linux/Documentation/kernel-parameters.txt
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   1                          Kernel Parameters
   2                          ~~~~~~~~~~~~~~~~~
   3
   4The following is a consolidated list of the kernel parameters as implemented
   5(mostly) by the __setup() macro and sorted into English Dictionary order
   6(defined as ignoring all punctuation and sorting digits before letters in a
   7case insensitive manner), and with descriptions where known.
   8
   9Module parameters for loadable modules are specified only as the
  10parameter name with optional '=' and value as appropriate, such as:
  11
  12        modprobe usbcore blinkenlights=1
  13
  14Module parameters for modules that are built into the kernel image
  15are specified on the kernel command line with the module name plus
  16'.' plus parameter name, with '=' and value if appropriate, such as:
  17
  18        usbcore.blinkenlights=1
  19
  20This document may not be entirely up to date and comprehensive. The command
  21"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  22module. Loadable modules, after being loaded into the running kernel, also
  23reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  24parameters may be changed at runtime by the command
  25"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  26
  27The parameters listed below are only valid if certain kernel build options were
  28enabled and if respective hardware is present. The text in square brackets at
  29the beginning of each description states the restrictions within which a
  30parameter is applicable:
  31
  32        ACPI    ACPI support is enabled.
  33        AGP     AGP (Accelerated Graphics Port) is enabled.
  34        ALSA    ALSA sound support is enabled.
  35        APIC    APIC support is enabled.
  36        APM     Advanced Power Management support is enabled.
  37        AVR32   AVR32 architecture is enabled.
  38        AX25    Appropriate AX.25 support is enabled.
  39        BLACKFIN Blackfin architecture is enabled.
  40        DRM     Direct Rendering Management support is enabled.
  41        EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
  42        EFI     EFI Partitioning (GPT) is enabled
  43        EIDE    EIDE/ATAPI support is enabled.
  44        FB      The frame buffer device is enabled.
  45        HW      Appropriate hardware is enabled.
  46        IA-64   IA-64 architecture is enabled.
  47        IOSCHED More than one I/O scheduler is enabled.
  48        IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
  49        ISAPNP  ISA PnP code is enabled.
  50        ISDN    Appropriate ISDN support is enabled.
  51        JOY     Appropriate joystick support is enabled.
  52        LIBATA  Libata driver is enabled
  53        LP      Printer support is enabled.
  54        LOOP    Loopback device support is enabled.
  55        M68k    M68k architecture is enabled.
  56                        These options have more detailed description inside of
  57                        Documentation/m68k/kernel-options.txt.
  58        MCA     MCA bus support is enabled.
  59        MDA     MDA console support is enabled.
  60        MOUSE   Appropriate mouse support is enabled.
  61        MSI     Message Signaled Interrupts (PCI).
  62        MTD     MTD (Memory Technology Device) support is enabled.
  63        NET     Appropriate network support is enabled.
  64        NUMA    NUMA support is enabled.
  65        GENERIC_TIME The generic timeofday code is enabled.
  66        NFS     Appropriate NFS support is enabled.
  67        OSS     OSS sound support is enabled.
  68        PV_OPS  A paravirtualized kernel is enabled.
  69        PARIDE  The ParIDE (parallel port IDE) subsystem is enabled.
  70        PARISC  The PA-RISC architecture is enabled.
  71        PCI     PCI bus support is enabled.
  72        PCIE    PCI Express support is enabled.
  73        PCMCIA  The PCMCIA subsystem is enabled.
  74        PNP     Plug & Play support is enabled.
  75        PPC     PowerPC architecture is enabled.
  76        PPT     Parallel port support is enabled.
  77        PS2     Appropriate PS/2 support is enabled.
  78        RAM     RAM disk support is enabled.
  79        ROOTPLUG The example Root Plug LSM is enabled.
  80        S390    S390 architecture is enabled.
  81        SCSI    Appropriate SCSI support is enabled.
  82                        A lot of drivers has their options described inside of
  83                        Documentation/scsi/.
  84        SECURITY Different security models are enabled.
  85        SELINUX SELinux support is enabled.
  86        SERIAL  Serial support is enabled.
  87        SH      SuperH architecture is enabled.
  88        SMP     The kernel is an SMP kernel.
  89        SPARC   Sparc architecture is enabled.
  90        SWSUSP  Software suspend (hibernation) is enabled.
  91        SUSPEND System suspend states are enabled.
  92        FTRACE  Function tracing enabled.
  93        TS      Appropriate touchscreen support is enabled.
  94        UMS     USB Mass Storage support is enabled.
  95        USB     USB support is enabled.
  96        USBHID  USB Human Interface Device support is enabled.
  97        V4L     Video For Linux support is enabled.
  98        VGA     The VGA console has been enabled.
  99        VT      Virtual terminal support is enabled.
 100        WDT     Watchdog support is enabled.
 101        XT      IBM PC/XT MFM hard disk support is enabled.
 102        X86-32  X86-32, aka i386 architecture is enabled.
 103        X86-64  X86-64 architecture is enabled.
 104                        More X86-64 boot options can be found in
 105                        Documentation/x86/x86_64/boot-options.txt .
 106        X86     Either 32bit or 64bit x86 (same as X86-32+X86-64)
 107
 108In addition, the following text indicates that the option:
 109
 110        BUGS=   Relates to possible processor bugs on the said processor.
 111        KNL     Is a kernel start-up parameter.
 112        BOOT    Is a boot loader parameter.
 113
 114Parameters denoted with BOOT are actually interpreted by the boot
 115loader, and have no meaning to the kernel directly.
 116Do not modify the syntax of boot loader parameters without extreme
 117need or coordination with <Documentation/x86/boot.txt>.
 118
 119There are also arch-specific kernel-parameters not documented here.
 120See for example <Documentation/x86/x86_64/boot-options.txt>.
 121
 122Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
 123a trailing = on the name of any parameter states that that parameter will
 124be entered as an environment variable, whereas its absence indicates that
 125it will appear as a kernel argument readable via /proc/cmdline by programs
 126running once the system is up.
 127
 128The number of kernel parameters is not limited, but the length of the
 129complete command line (parameters including spaces etc.) is limited to
 130a fixed number of characters. This limit depends on the architecture
 131and is between 256 and 4096 characters. It is defined in the file
 132./include/asm/setup.h as COMMAND_LINE_SIZE.
 133
 134
 135        acpi=           [HW,ACPI,X86-64,i386]
 136                        Advanced Configuration and Power Interface
 137                        Format: { force | off | ht | strict | noirq | rsdt }
 138                        force -- enable ACPI if default was off
 139                        off -- disable ACPI if default was on
 140                        noirq -- do not use ACPI for IRQ routing
 141                        ht -- run only enough ACPI to enable Hyper Threading
 142                        strict -- Be less tolerant of platforms that are not
 143                                strictly ACPI specification compliant.
 144                        rsdt -- prefer RSDT over (default) XSDT
 145
 146                        See also Documentation/power/pm.txt, pci=noacpi
 147
 148        acpi_apic_instance=     [ACPI, IOAPIC]
 149                        Format: <int>
 150                        2: use 2nd APIC table, if available
 151                        1,0: use 1st APIC table
 152                        default: 0
 153
 154        acpi_sleep=     [HW,ACPI] Sleep options
 155                        Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
 156                                  old_ordering, s4_nonvs }
 157                        See Documentation/power/video.txt for information on
 158                        s3_bios and s3_mode.
 159                        s3_beep is for debugging; it makes the PC's speaker beep
 160                        as soon as the kernel's real-mode entry point is called.
 161                        s4_nohwsig prevents ACPI hardware signature from being
 162                        used during resume from hibernation.
 163                        old_ordering causes the ACPI 1.0 ordering of the _PTS
 164                        control method, with respect to putting devices into
 165                        low power states, to be enforced (the ACPI 2.0 ordering
 166                        of _PTS is used by default).
 167                        s4_nonvs prevents the kernel from saving/restoring the
 168                        ACPI NVS memory during hibernation.
 169
 170        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
 171                        Format: { level | edge | high | low }
 172
 173        acpi_irq_balance [HW,ACPI]
 174                        ACPI will balance active IRQs
 175                        default in APIC mode
 176
 177        acpi_irq_nobalance [HW,ACPI]
 178                        ACPI will not move active IRQs (default)
 179                        default in PIC mode
 180
 181        acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
 182                        use by PCI
 183                        Format: <irq>,<irq>...
 184
 185        acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
 186                        Format: <irq>,<irq>...
 187
 188        acpi_no_auto_ssdt       [HW,ACPI] Disable automatic loading of SSDT
 189
 190        acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
 191                        Format: To spoof as Windows 98: ="Microsoft Windows"
 192
 193        acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
 194                        acpi_osi="string1"      # add string1 -- only one string
 195                        acpi_osi="!string2"     # remove built-in string2
 196                        acpi_osi=               # disable all strings
 197
 198        acpi_serialize  [HW,ACPI] force serialization of AML methods
 199
 200        acpi_skip_timer_override [HW,ACPI]
 201                        Recognize and ignore IRQ0/pin2 Interrupt Override.
 202                        For broken nForce2 BIOS resulting in XT-PIC timer.
 203        acpi_use_timer_override [HW,ACPI]
 204                        Use timer override. For some broken Nvidia NF5 boards
 205                        that require a timer override, but don't have
 206                        HPET
 207
 208        acpi_backlight= [HW,ACPI]
 209                        acpi_backlight=vendor
 210                        acpi_backlight=video
 211                        If set to vendor, prefer vendor specific driver
 212                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
 213                        of the ACPI video.ko driver.
 214
 215        acpi_display_output=    [HW,ACPI]
 216                        acpi_display_output=vendor
 217                        acpi_display_output=video
 218                        See above.
 219
 220        acpi.debug_layer=       [HW,ACPI,ACPI_DEBUG]
 221        acpi.debug_level=       [HW,ACPI,ACPI_DEBUG]
 222                        Format: <int>
 223                        CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
 224                        debug output.  Bits in debug_layer correspond to a
 225                        _COMPONENT in an ACPI source file, e.g.,
 226                            #define _COMPONENT ACPI_PCI_COMPONENT
 227                        Bits in debug_level correspond to a level in
 228                        ACPI_DEBUG_PRINT statements, e.g.,
 229                            ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
 230                        The debug_level mask defaults to "info".  See
 231                        Documentation/acpi/debug.txt for more information about
 232                        debug layers and levels.
 233
 234                        Enable processor driver info messages:
 235                            acpi.debug_layer=0x20000000
 236                        Enable PCI/PCI interrupt routing info messages:
 237                            acpi.debug_layer=0x400000
 238                        Enable AML "Debug" output, i.e., stores to the Debug
 239                        object while interpreting AML:
 240                            acpi.debug_layer=0xffffffff acpi.debug_level=0x2
 241                        Enable all messages related to ACPI hardware:
 242                            acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
 243
 244                        Some values produce so much output that the system is
 245                        unusable.  The "log_buf_len" parameter may be useful
 246                        if you need to capture more output.
 247
 248        acpi.power_nocheck=     [HW,ACPI]
 249                        Format: 1/0 enable/disable the check of power state.
 250                        On some bogus BIOS the _PSC object/_STA object of
 251                        power resource can't return the correct device power
 252                        state. In such case it is unneccessary to check its
 253                        power state again in power transition.
 254                        1 : disable the power state check
 255
 256        acpi_pm_good    [X86-32,X86-64]
 257                        Override the pmtimer bug detection: force the kernel
 258                        to assume that this machine's pmtimer latches its value
 259                        and always returns good values.
 260
 261        agp=            [AGP]
 262                        { off | try_unsupported }
 263                        off: disable AGP support
 264                        try_unsupported: try to drive unsupported chipsets
 265                                (may crash computer or cause data corruption)
 266
 267        enable_timer_pin_1 [i386,x86-64]
 268                        Enable PIN 1 of APIC timer
 269                        Can be useful to work around chipset bugs
 270                        (in particular on some ATI chipsets).
 271                        The kernel tries to set a reasonable default.
 272
 273        disable_timer_pin_1 [i386,x86-64]
 274                        Disable PIN 1 of APIC timer
 275                        Can be useful to work around chipset bugs.
 276
 277        ad1848=         [HW,OSS]
 278                        Format: <io>,<irq>,<dma>,<dma2>,<type>
 279
 280        advansys=       [HW,SCSI]
 281                        See header of drivers/scsi/advansys.c.
 282
 283        advwdt=         [HW,WDT] Advantech WDT
 284                        Format: <iostart>,<iostop>
 285
 286        aedsp16=        [HW,OSS] Audio Excel DSP 16
 287                        Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
 288                        See also header of sound/oss/aedsp16.c.
 289
 290        aha152x=        [HW,SCSI]
 291                        See Documentation/scsi/aha152x.txt.
 292
 293        aha1542=        [HW,SCSI]
 294                        Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
 295
 296        aic7xxx=        [HW,SCSI]
 297                        See Documentation/scsi/aic7xxx.txt.
 298
 299        aic79xx=        [HW,SCSI]
 300                        See Documentation/scsi/aic79xx.txt.
 301
 302        amd_iommu=      [HW,X86-84]
 303                        Pass parameters to the AMD IOMMU driver in the system.
 304                        Possible values are:
 305                        isolate - enable device isolation (each device, as far
 306                                  as possible, will get its own protection
 307                                  domain) [default]
 308                        share - put every device behind one IOMMU into the
 309                                same protection domain
 310                        fullflush - enable flushing of IO/TLB entries when
 311                                    they are unmapped. Otherwise they are
 312                                    flushed before they will be reused, which
 313                                    is a lot of faster
 314
 315        amd_iommu_size= [HW,X86-64]
 316                        Define the size of the aperture for the AMD IOMMU
 317                        driver. Possible values are:
 318                        '32M', '64M' (default), '128M', '256M', '512M', '1G'
 319
 320        amijoy.map=     [HW,JOY] Amiga joystick support
 321                        Map of devices attached to JOY0DAT and JOY1DAT
 322                        Format: <a>,<b>
 323                        See also Documentation/kernel/input/joystick.txt
 324
 325        analog.map=     [HW,JOY] Analog joystick and gamepad support
 326                        Specifies type or capabilities of an analog joystick
 327                        connected to one of 16 gameports
 328                        Format: <type1>,<type2>,..<type16>
 329
 330        apc=            [HW,SPARC]
 331                        Power management functions (SPARCstation-4/5 + deriv.)
 332                        Format: noidle
 333                        Disable APC CPU standby support. SPARCstation-Fox does
 334                        not play well with APC CPU idle - disable it if you have
 335                        APC and your system crashes randomly.
 336
 337        apic=           [APIC,i386] Advanced Programmable Interrupt Controller
 338                        Change the output verbosity whilst booting
 339                        Format: { quiet (default) | verbose | debug }
 340                        Change the amount of debugging information output
 341                        when initialising the APIC and IO-APIC components.
 342
 343        apm=            [APM] Advanced Power Management
 344                        See header of arch/x86/kernel/apm_32.c.
 345
 346        arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
 347                        Format: <io>,<irq>,<nodeID>
 348
 349        ataflop=        [HW,M68k]
 350
 351        atarimouse=     [HW,MOUSE] Atari Mouse
 352
 353        atascsi=        [HW,SCSI] Atari SCSI
 354
 355        atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
 356                        EzKey and similar keyboards
 357
 358        atkbd.reset=    [HW] Reset keyboard during initialization
 359
 360        atkbd.set=      [HW] Select keyboard code set
 361                        Format: <int> (2 = AT (default), 3 = PS/2)
 362
 363        atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
 364                        keyboards
 365
 366        atkbd.softraw=  [HW] Choose between synthetic and real raw mode
 367                        Format: <bool> (0 = real, 1 = synthetic (default))
 368
 369        atkbd.softrepeat= [HW]
 370                        Use software keyboard repeat
 371
 372        autotest        [IA64]
 373
 374        baycom_epp=     [HW,AX25]
 375                        Format: <io>,<mode>
 376
 377        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
 378                        Format: <io>,<mode>
 379                        See header of drivers/net/hamradio/baycom_par.c.
 380
 381        baycom_ser_fdx= [HW,AX25]
 382                        BayCom Serial Port AX.25 Modem (Full Duplex Mode)
 383                        Format: <io>,<irq>,<mode>[,<baud>]
 384                        See header of drivers/net/hamradio/baycom_ser_fdx.c.
 385
 386        baycom_ser_hdx= [HW,AX25]
 387                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
 388                        Format: <io>,<irq>,<mode>
 389                        See header of drivers/net/hamradio/baycom_ser_hdx.c.
 390
 391        boot_delay=     Milliseconds to delay each printk during boot.
 392                        Values larger than 10 seconds (10000) are changed to
 393                        no delay (0).
 394                        Format: integer
 395
 396        bootmem_debug   [KNL] Enable bootmem allocator debug messages.
 397
 398        bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
 399        bttv.radio=     Most important insmod options are available as
 400                        kernel args too.
 401        bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
 402        bttv.tuner=     and Documentation/video4linux/bttv/CARDLIST
 403
 404        BusLogic=       [HW,SCSI]
 405                        See drivers/scsi/BusLogic.c, comment before function
 406                        BusLogic_ParseDriverOptions().
 407
 408        c101=           [NET] Moxa C101 synchronous serial card
 409
 410        cachesize=      [BUGS=X86-32] Override level 2 CPU cache size detection.
 411                        Sometimes CPU hardware bugs make them report the cache
 412                        size incorrectly. The kernel will attempt work arounds
 413                        to fix known problems, but for some CPUs it is not
 414                        possible to determine what the correct size should be.
 415                        This option provides an override for these situations.
 416
 417        security=       [SECURITY] Choose a security module to enable at boot.
 418                        If this boot parameter is not specified, only the first
 419                        security module asking for security registration will be
 420                        loaded. An invalid security module name will be treated
 421                        as if no module has been chosen.
 422
 423        capability.disable=
 424                        [SECURITY] Disable capabilities.  This would normally
 425                        be used only if an alternative security model is to be
 426                        configured.  Potentially dangerous and should only be
 427                        used if you are entirely sure of the consequences.
 428
 429        ccw_timeout_log [S390]
 430                        See Documentation/s390/CommonIO for details.
 431
 432        cgroup_disable= [KNL] Disable a particular controller
 433                        Format: {name of the controller(s) to disable}
 434                                {Currently supported controllers - "memory"}
 435
 436        checkreqprot    [SELINUX] Set initial checkreqprot flag value.
 437                        Format: { "0" | "1" }
 438                        See security/selinux/Kconfig help text.
 439                        0 -- check protection applied by kernel (includes
 440                                any implied execute protection).
 441                        1 -- check protection requested by application.
 442                        Default value is set via a kernel config option.
 443                        Value can be changed at runtime via
 444                                /selinux/checkreqprot.
 445
 446        cio_ignore=     [S390]
 447                        See Documentation/s390/CommonIO for details.
 448
 449        clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
 450                        [Deprecated]
 451                        Forces specified clocksource (if available) to be used
 452                        when calculating gettimeofday(). If specified
 453                        clocksource is not available, it defaults to PIT.
 454                        Format: { pit | tsc | cyclone | pmtmr }
 455
 456        clocksource=    [GENERIC_TIME] Override the default clocksource
 457                        Format: <string>
 458                        Override the default clocksource and use the clocksource
 459                        with the name specified.
 460                        Some clocksource names to choose from, depending on
 461                        the platform:
 462                        [all] jiffies (this is the base, fallback clocksource)
 463                        [ACPI] acpi_pm
 464                        [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
 465                                pxa_timer,timer3,32k_counter,timer0_1
 466                        [AVR32] avr32
 467                        [X86-32] pit,hpet,tsc,vmi-timer;
 468                                scx200_hrt on Geode; cyclone on IBM x440
 469                        [MIPS] MIPS
 470                        [PARISC] cr16
 471                        [S390] tod
 472                        [SH] SuperH
 473                        [SPARC64] tick
 474                        [X86-64] hpet,tsc
 475
 476        clearcpuid=BITNUM [X86]
 477                        Disable CPUID feature X for the kernel. See
 478                        arch/x86/include/asm/cpufeature.h for the valid bit
 479                        numbers. Note the Linux specific bits are not necessarily
 480                        stable over kernel options, but the vendor specific
 481                        ones should be.
 482                        Also note that user programs calling CPUID directly
 483                        or using the feature without checking anything
 484                        will still see it. This just prevents it from
 485                        being used by the kernel or shown in /proc/cpuinfo.
 486                        Also note the kernel might malfunction if you disable
 487                        some critical bits.
 488
 489        code_bytes      [IA32/X86_64] How many bytes of object code to print
 490                        in an oops report.
 491                        Range: 0 - 8192
 492                        Default: 64
 493
 494        hpet=           [X86-32,HPET] option to control HPET usage
 495                        Format: { enable (default) | disable | force }
 496                        disable: disable HPET and use PIT instead
 497                        force: allow force enabled of undocumented chips (ICH4,
 498                        VIA, nVidia)
 499
 500        com20020=       [HW,NET] ARCnet - COM20020 chipset
 501                        Format:
 502                        <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
 503
 504        com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
 505                        Format: <io>[,<irq>]
 506
 507        com90xx=        [HW,NET]
 508                        ARCnet - COM90xx chipset (memory-mapped buffers)
 509                        Format: <io>[,<irq>[,<memstart>]]
 510
 511        condev=         [HW,S390] console device
 512        conmode=
 513
 514        console=        [KNL] Output console device and options.
 515
 516                tty<n>  Use the virtual console device <n>.
 517
 518                ttyS<n>[,options]
 519                ttyUSB0[,options]
 520                        Use the specified serial port.  The options are of
 521                        the form "bbbbpnf", where "bbbb" is the baud rate,
 522                        "p" is parity ("n", "o", or "e"), "n" is number of
 523                        bits, and "f" is flow control ("r" for RTS or
 524                        omit it).  Default is "9600n8".
 525
 526                        See Documentation/serial-console.txt for more
 527                        information.  See
 528                        Documentation/networking/netconsole.txt for an
 529                        alternative.
 530
 531                uart[8250],io,<addr>[,options]
 532                uart[8250],mmio,<addr>[,options]
 533                        Start an early, polled-mode console on the 8250/16550
 534                        UART at the specified I/O port or MMIO address,
 535                        switching to the matching ttyS device later.  The
 536                        options are the same as for ttyS, above.
 537
 538                If the device connected to the port is not a TTY but a braille
 539                device, prepend "brl," before the device type, for instance
 540                        console=brl,ttyS0
 541                For now, only VisioBraille is supported.
 542
 543        earlycon=       [KNL] Output early console device and options.
 544                uart[8250],io,<addr>[,options]
 545                uart[8250],mmio,<addr>[,options]
 546                        Start an early, polled-mode console on the 8250/16550
 547                        UART at the specified I/O port or MMIO address.
 548                        The options are the same as for ttyS, above.
 549
 550        no_console_suspend
 551                        [HW] Never suspend the console
 552                        Disable suspending of consoles during suspend and
 553                        hibernate operations.  Once disabled, debugging
 554                        messages can reach various consoles while the rest
 555                        of the system is being put to sleep (ie, while
 556                        debugging driver suspend/resume hooks).  This may
 557                        not work reliably with all consoles, but is known
 558                        to work with serial and VGA consoles.
 559
 560        coredump_filter=
 561                        [KNL] Change the default value for
 562                        /proc/<pid>/coredump_filter.
 563                        See also Documentation/filesystems/proc.txt.
 564
 565        cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
 566                        Format:
 567                        <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
 568
 569        crashkernel=nn[KMG]@ss[KMG]
 570                        [KNL] Reserve a chunk of physical memory to
 571                        hold a kernel to switch to with kexec on panic.
 572
 573        crashkernel=range1:size1[,range2:size2,...][@offset]
 574                        [KNL] Same as above, but depends on the memory
 575                        in the running system. The syntax of range is
 576                        start-[end] where start and end are both
 577                        a memory unit (amount[KMG]). See also
 578                        Documentation/kdump/kdump.txt for a example.
 579
 580        cs89x0_dma=     [HW,NET]
 581                        Format: <dma>
 582
 583        cs89x0_media=   [HW,NET]
 584                        Format: { rj45 | aui | bnc }
 585
 586        dasd=           [HW,NET]
 587                        See header of drivers/s390/block/dasd_devmap.c.
 588
 589        db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
 590                        (one device per port)
 591                        Format: <port#>,<type>
 592                        See also Documentation/input/joystick-parport.txt
 593
 594        debug           [KNL] Enable kernel debugging (events log level).
 595
 596        debug_locks_verbose=
 597                        [KNL] verbose self-tests
 598                        Format=<0|1>
 599                        Print debugging info while doing the locking API
 600                        self-tests.
 601                        We default to 0 (no extra messages), setting it to
 602                        1 will print _a lot_ more information - normally
 603                        only useful to kernel developers.
 604
 605        debug_objects   [KNL] Enable object debugging
 606
 607        debugpat        [X86] Enable PAT debugging
 608
 609        decnet.addr=    [HW,NET]
 610                        Format: <area>[,<node>]
 611                        See also Documentation/networking/decnet.txt.
 612
 613        vt.default_blu= [VT]
 614                        Format: <blue0>,<blue1>,<blue2>,...,<blue15>
 615                        Change the default blue palette of the console.
 616                        This is a 16-member array composed of values
 617                        ranging from 0-255.
 618
 619        vt.default_grn= [VT]
 620                        Format: <green0>,<green1>,<green2>,...,<green15>
 621                        Change the default green palette of the console.
 622                        This is a 16-member array composed of values
 623                        ranging from 0-255.
 624
 625        vt.default_red= [VT]
 626                        Format: <red0>,<red1>,<red2>,...,<red15>
 627                        Change the default red palette of the console.
 628                        This is a 16-member array composed of values
 629                        ranging from 0-255.
 630
 631        vt.default_utf8=
 632                        [VT]
 633                        Format=<0|1>
 634                        Set system-wide default UTF-8 mode for all tty's.
 635                        Default is 1, i.e. UTF-8 mode is enabled for all
 636                        newly opened terminals.
 637
 638        dhash_entries=  [KNL]
 639                        Set number of hash buckets for dentry cache.
 640
 641        digi=           [HW,SERIAL]
 642                        IO parameters + enable/disable command.
 643
 644        digiepca=       [HW,SERIAL]
 645                        See drivers/char/README.epca and
 646                        Documentation/serial/digiepca.txt.
 647
 648        disable_mtrr_cleanup [X86]
 649        enable_mtrr_cleanup [X86]
 650                        The kernel tries to adjust MTRR layout from continuous
 651                        to discrete, to make X server driver able to add WB
 652                        entry later. This parameter enables/disables that.
 653
 654        mtrr_chunk_size=nn[KMG] [X86]
 655                        used for mtrr cleanup. It is largest continous chunk
 656                        that could hold holes aka. UC entries.
 657
 658        mtrr_gran_size=nn[KMG] [X86]
 659                        Used for mtrr cleanup. It is granularity of mtrr block.
 660                        Default is 1.
 661                        Large value could prevent small alignment from
 662                        using up MTRRs.
 663
 664        mtrr_spare_reg_nr=n [X86]
 665                        Format: <integer>
 666                        Range: 0,7 : spare reg number
 667                        Default : 1
 668                        Used for mtrr cleanup. It is spare mtrr entries number.
 669                        Set to 2 or more if your graphical card needs more.
 670
 671        disable_mtrr_trim [X86, Intel and AMD only]
 672                        By default the kernel will trim any uncacheable
 673                        memory out of your available memory pool based on
 674                        MTRR settings.  This parameter disables that behavior,
 675                        possibly causing your machine to run very slowly.
 676
 677        dmasound=       [HW,OSS] Sound subsystem buffers
 678
 679        dscc4.setup=    [NET]
 680
 681        dtc3181e=       [HW,SCSI]
 682
 683        earlyprintk=    [X86-32,X86-64,SH,BLACKFIN]
 684                        earlyprintk=vga
 685                        earlyprintk=serial[,ttySn[,baudrate]]
 686                        earlyprintk=dbgp
 687
 688                        Append ",keep" to not disable it when the real console
 689                        takes over.
 690
 691                        Only vga or serial or usb debug port at a time.
 692
 693                        Currently only ttyS0 and ttyS1 are supported.
 694
 695                        Interaction with the standard serial driver is not
 696                        very good.
 697
 698                        The VGA output is eventually overwritten by the real
 699                        console.
 700
 701        eata=           [HW,SCSI]
 702
 703        edd=            [EDD]
 704                        Format: {"off" | "on" | "skip[mbr]"}
 705
 706        eisa_irq_edge=  [PARISC,HW]
 707                        See header of drivers/parisc/eisa.c.
 708
 709        elanfreq=       [X86-32]
 710                        See comment before function elanfreq_setup() in
 711                        arch/x86/kernel/cpu/cpufreq/elanfreq.c.
 712
 713        elevator=       [IOSCHED]
 714                        Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
 715                        See Documentation/block/as-iosched.txt and
 716                        Documentation/block/deadline-iosched.txt for details.
 717
 718        elfcorehdr=     [IA64,PPC,SH,X86-32,X86_64]
 719                        Specifies physical address of start of kernel core
 720                        image elf header. Generally kexec loader will
 721                        pass this option to capture kernel.
 722                        See Documentation/kdump/kdump.txt for details.
 723
 724        enforcing       [SELINUX] Set initial enforcing status.
 725                        Format: {"0" | "1"}
 726                        See security/selinux/Kconfig help text.
 727                        0 -- permissive (log only, no denials).
 728                        1 -- enforcing (deny and log).
 729                        Default value is 0.
 730                        Value can be changed at runtime via /selinux/enforce.
 731
 732        ether=          [HW,NET] Ethernet cards parameters
 733                        This option is obsoleted by the "netdev=" option, which
 734                        has equivalent usage. See its documentation for details.
 735
 736        eurwdt=         [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
 737                        Format: <io>[,<irq>]
 738
 739        failslab=
 740        fail_page_alloc=
 741        fail_make_request=[KNL]
 742                        General fault injection mechanism.
 743                        Format: <interval>,<probability>,<space>,<times>
 744                        See also /Documentation/fault-injection/.
 745
 746        fd_mcs=         [HW,SCSI]
 747                        See header of drivers/scsi/fd_mcs.c.
 748
 749        fdomain=        [HW,SCSI]
 750                        See header of drivers/scsi/fdomain.c.
 751
 752        floppy=         [HW]
 753                        See Documentation/blockdev/floppy.txt.
 754
 755        force_pal_cache_flush
 756                        [IA-64] Avoid check_sal_cache_flush which may hang on
 757                        buggy SAL_CACHE_FLUSH implementations. Using this
 758                        parameter will force ia64_sal_cache_flush to call
 759                        ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
 760
 761        ftrace=[tracer]
 762                        [ftrace] will set and start the specified tracer
 763                        as early as possible in order to facilitate early
 764                        boot debugging.
 765
 766        ftrace_dump_on_oops
 767                        [ftrace] will dump the trace buffers on oops.
 768
 769        gamecon.map[2|3]=
 770                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
 771                        support via parallel port (up to 5 devices per port)
 772                        Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
 773                        See also Documentation/input/joystick-parport.txt
 774
 775        gamma=          [HW,DRM]
 776
 777        gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
 778                        Format: off | on
 779                        default: on
 780
 781        gdth=           [HW,SCSI]
 782                        See header of drivers/scsi/gdth.c.
 783
 784        gpt             [EFI] Forces disk with valid GPT signature but
 785                        invalid Protective MBR to be treated as GPT.
 786
 787        gvp11=          [HW,SCSI]
 788
 789        hashdist=       [KNL,NUMA] Large hashes allocated during boot
 790                        are distributed across NUMA nodes.  Defaults on
 791                        for IA-64, off otherwise.
 792                        Format: 0 | 1 (for off | on)
 793
 794        hcl=            [IA-64] SGI's Hardware Graph compatibility layer
 795
 796        hd=             [EIDE] (E)IDE hard drive subsystem geometry
 797                        Format: <cyl>,<head>,<sect>
 798
 799        highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
 800                        size of <nn>. This works even on boxes that have no
 801                        highmem otherwise. This also works to reduce highmem
 802                        size on bigger boxes.
 803
 804        highres=        [KNL] Enable/disable high resolution timer mode.
 805                        Valid parameters: "on", "off"
 806                        Default: "on"
 807
 808        hisax=          [HW,ISDN]
 809                        See Documentation/isdn/README.HiSax.
 810
 811        hugepages=      [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
 812        hugepagesz=     [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
 813                        On x86-64 and powerpc, this option can be specified
 814                        multiple times interleaved with hugepages= to reserve
 815                        huge pages of different sizes. Valid pages sizes on
 816                        x86-64 are 2M (when the CPU supports "pse") and 1G
 817                        (when the CPU supports the "pdpe1gb" cpuinfo flag)
 818                        Note that 1GB pages can only be allocated at boot time
 819                        using hugepages= and not freed afterwards.
 820        default_hugepagesz=
 821                        [same as hugepagesz=] The size of the default
 822                        HugeTLB page size. This is the size represented by
 823                        the legacy /proc/ hugepages APIs, used for SHM, and
 824                        default size when mounting hugetlbfs filesystems.
 825                        Defaults to the default architecture's huge page size
 826                        if not specified.
 827
 828        hlt             [BUGS=ARM,SH]
 829
 830        hvc_iucv=       [S390] Number of z/VM IUCV hypervisor console (HVC)
 831                               terminal devices. Valid values: 0..8
 832
 833        i8042.debug     [HW] Toggle i8042 debug mode
 834        i8042.direct    [HW] Put keyboard port into non-translated mode
 835        i8042.dumbkbd   [HW] Pretend that controller can only read data from
 836                             keyboard and cannot control its state
 837                             (Don't attempt to blink the leds)
 838        i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
 839        i8042.nokbd     [HW] Don't check/create keyboard port
 840        i8042.noloop    [HW] Disable the AUX Loopback command while probing
 841                             for the AUX port
 842        i8042.nomux     [HW] Don't check presence of an active multiplexing
 843                             controller
 844        i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
 845                             controllers
 846        i8042.panicblink=
 847                        [HW] Frequency with which keyboard LEDs should blink
 848                             when kernel panics (default is 0.5 sec)
 849        i8042.reset     [HW] Reset the controller during init and cleanup
 850        i8042.unlock    [HW] Unlock (ignore) the keylock
 851
 852        i810=           [HW,DRM]
 853
 854        i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
 855                        indicates that the driver is running on unsupported
 856                        hardware.
 857        i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
 858                        does not match list of supported models.
 859        i8k.power_status
 860                        [HW] Report power status in /proc/i8k
 861                        (disabled by default)
 862        i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
 863                        capability is set.
 864
 865        ibmmcascsi=     [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
 866                        See Documentation/mca.txt.
 867
 868        icn=            [HW,ISDN]
 869                        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
 870
 871        ide-core.nodma= [HW] (E)IDE subsystem
 872                        Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
 873                        .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
 874                        .chs .ignore_cable are additional options
 875                        See Documentation/ide/ide.txt.
 876
 877        idebus=         [HW] (E)IDE subsystem - VLB/PCI bus speed
 878                        See Documentation/ide/ide.txt.
 879
 880        idle=           [X86]
 881                        Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
 882                        Poll forces a polling idle loop that can slightly
 883                        improve the performance of waking up a idle CPU, but
 884                        will use a lot of power and make the system run hot.
 885                        Not recommended.
 886                        idle=mwait: On systems which support MONITOR/MWAIT but
 887                        the kernel chose to not use it because it doesn't save
 888                        as much power as a normal idle loop, use the
 889                        MONITOR/MWAIT idle loop anyways. Performance should be
 890                        the same as idle=poll.
 891                        idle=halt: Halt is forced to be used for CPU idle.
 892                        In such case C2/C3 won't be used again.
 893                        idle=nomwait: Disable mwait for CPU C-states
 894
 895        ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
 896                        Claim all unknown PCI IDE storage controllers.
 897
 898        ignore_loglevel [KNL]
 899                        Ignore loglevel setting - this will print /all/
 900                        kernel messages to the console. Useful for debugging.
 901
 902        ihash_entries=  [KNL]
 903                        Set number of hash buckets for inode cache.
 904
 905        in2000=         [HW,SCSI]
 906                        See header of drivers/scsi/in2000.c.
 907
 908        init=           [KNL]
 909                        Format: <full_path>
 910                        Run specified binary instead of /sbin/init as init
 911                        process.
 912
 913        initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
 914                        for working out where the kernel is dying during
 915                        startup.
 916
 917        initrd=         [BOOT] Specify the location of the initial ramdisk
 918
 919        inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
 920                        Format: <irq>
 921
 922        inttest=        [IA64]
 923
 924        iomem=          Disable strict checking of access to MMIO memory
 925                strict  regions from userspace.
 926                relaxed
 927
 928        iommu=          [x86]
 929                off
 930                force
 931                noforce
 932                biomerge
 933                panic
 934                nopanic
 935                merge
 936                nomerge
 937                forcesac
 938                soft
 939
 940
 941        intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
 942                on
 943                        Enable intel iommu driver.
 944                off
 945                        Disable intel iommu driver.
 946                igfx_off [Default Off]
 947                        By default, gfx is mapped as normal device. If a gfx
 948                        device has a dedicated DMAR unit, the DMAR unit is
 949                        bypassed by not enabling DMAR with this option. In
 950                        this case, gfx device will use physical address for
 951                        DMA.
 952                forcedac [x86_64]
 953                        With this option iommu will not optimize to look
 954                        for io virtual address below 32 bit forcing dual
 955                        address cycle on pci bus for cards supporting greater
 956                        than 32 bit addressing. The default is to look
 957                        for translation below 32 bit and if not available
 958                        then look in the higher range.
 959                strict [Default Off]
 960                        With this option on every unmap_single operation will
 961                        result in a hardware IOTLB flush operation as opposed
 962                        to batching them for performance.
 963
 964        io_delay=       [X86-32,X86-64] I/O delay method
 965                0x80
 966                        Standard port 0x80 based delay
 967                0xed
 968                        Alternate port 0xed based delay (needed on some systems)
 969                udelay
 970                        Simple two microseconds delay
 971                none
 972                        No delay
 973
 974        io7=            [HW] IO7 for Marvel based alpha systems
 975                        See comment before marvel_specify_io7 in
 976                        arch/alpha/kernel/core_marvel.c.
 977
 978        ip=             [IP_PNP]
 979                        See Documentation/filesystems/nfsroot.txt.
 980
 981        ip2=            [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
 982                        See comment before ip2_setup() in
 983                        drivers/char/ip2/ip2base.c.
 984
 985        ips=            [HW,SCSI] Adaptec / IBM ServeRAID controller
 986                        See header of drivers/scsi/ips.c.
 987
 988        ports=          [IP_VS_FTP] IPVS ftp helper module
 989                        Default is 21.
 990                        Up to 8 (IP_VS_APP_MAX_PORTS) ports
 991                        may be specified.
 992                        Format: <port>,<port>....
 993
 994        irqfixup        [HW]
 995                        When an interrupt is not handled search all handlers
 996                        for it. Intended to get systems with badly broken
 997                        firmware running.
 998
 999        irqpoll         [HW]
1000                        When an interrupt is not handled search all handlers
1001                        for it. Also check all handlers each timer
1002                        interrupt. Intended to get systems with badly broken
1003                        firmware running.
1004
1005        isapnp=         [ISAPNP]
1006                        Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1007
1008        isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
1009                        Format:
1010                        <cpu number>,...,<cpu number>
1011                        or
1012                        <cpu number>-<cpu number>
1013                        (must be a positive range in ascending order)
1014                        or a mixture
1015                        <cpu number>,...,<cpu number>-<cpu number>
1016
1017                        This option can be used to specify one or more CPUs
1018                        to isolate from the general SMP balancing and scheduling
1019                        algorithms. You can move a process onto or off an
1020                        "isolated" CPU via the CPU affinity syscalls or cpuset.
1021                        <cpu number> begins at 0 and the maximum value is
1022                        "number of CPUs in system - 1".
1023
1024                        This option is the preferred way to isolate CPUs. The
1025                        alternative -- manually setting the CPU mask of all
1026                        tasks in the system -- can cause problems and
1027                        suboptimal load balancer performance.
1028
1029        iucv=           [HW,NET]
1030
1031        js=             [HW,JOY] Analog joystick
1032                        See Documentation/input/joystick.txt.
1033
1034        kernelcore=nn[KMG]      [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1035                        specifies the amount of memory usable by the kernel
1036                        for non-movable allocations.  The requested amount is
1037                        spread evenly throughout all nodes in the system. The
1038                        remaining memory in each node is used for Movable
1039                        pages. In the event, a node is too small to have both
1040                        kernelcore and Movable pages, kernelcore pages will
1041                        take priority and other nodes will have a larger number
1042                        of kernelcore pages.  The Movable zone is used for the
1043                        allocation of pages that may be reclaimed or moved
1044                        by the page migration subsystem.  This means that
1045                        HugeTLB pages may not be allocated from this zone.
1046                        Note that allocations like PTEs-from-HighMem still
1047                        use the HighMem zone if it exists, and the Normal
1048                        zone if it does not.
1049
1050        movablecore=nn[KMG]     [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1051                        is similar to kernelcore except it specifies the
1052                        amount of memory used for migratable allocations.
1053                        If both kernelcore and movablecore is specified,
1054                        then kernelcore will be at *least* the specified
1055                        value but may be more. If movablecore on its own
1056                        is specified, the administrator must be careful
1057                        that the amount of memory usable for all allocations
1058                        is not too small.
1059
1060        keepinitrd      [HW,ARM]
1061
1062        kstack=N        [X86-32,X86-64] Print N words from the kernel stack
1063                        in oops dumps.
1064
1065        kgdboc=         [HW] kgdb over consoles.
1066                        Requires a tty driver that supports console polling.
1067                        (only serial suported for now)
1068                        Format: <serial_device>[,baud]
1069
1070        kmac=           [MIPS] korina ethernet MAC address.
1071                        Configure the RouterBoard 532 series on-chip
1072                        Ethernet adapter MAC address.
1073
1074        l2cr=           [PPC]
1075
1076        l3cr=           [PPC]
1077
1078        lapic           [X86-32,APIC] Enable the local APIC even if BIOS
1079                        disabled it.
1080
1081        lapic_timer_c2_ok       [X86-32,x86-64,APIC] trust the local apic timer
1082                        in C2 power state.
1083
1084        libata.dma=     [LIBATA] DMA control
1085                        libata.dma=0      Disable all PATA and SATA DMA
1086                        libata.dma=1      PATA and SATA Disk DMA only
1087                        libata.dma=2      ATAPI (CDROM) DMA only
1088                        libata.dma=4      Compact Flash DMA only 
1089                        Combinations also work, so libata.dma=3 enables DMA
1090                        for disks and CDROMs, but not CFs.
1091
1092        libata.noacpi   [LIBATA] Disables use of ACPI in libata suspend/resume
1093                        when set.
1094                        Format: <int>
1095
1096        libata.force=   [LIBATA] Force configurations.  The format is comma
1097                        separated list of "[ID:]VAL" where ID is
1098                        PORT[:DEVICE].  PORT and DEVICE are decimal numbers
1099                        matching port, link or device.  Basically, it matches
1100                        the ATA ID string printed on console by libata.  If
1101                        the whole ID part is omitted, the last PORT and DEVICE
1102                        values are used.  If ID hasn't been specified yet, the
1103                        configuration applies to all ports, links and devices.
1104
1105                        If only DEVICE is omitted, the parameter applies to
1106                        the port and all links and devices behind it.  DEVICE
1107                        number of 0 either selects the first device or the
1108                        first fan-out link behind PMP device.  It does not
1109                        select the host link.  DEVICE number of 15 selects the
1110                        host link and device attached to it.
1111
1112                        The VAL specifies the configuration to force.  As long
1113                        as there's no ambiguity shortcut notation is allowed.
1114                        For example, both 1.5 and 1.5G would work for 1.5Gbps.
1115                        The following configurations can be forced.
1116
1117                        * Cable type: 40c, 80c, short40c, unk, ign or sata.
1118                          Any ID with matching PORT is used.
1119
1120                        * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1121
1122                        * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1123                          udma[/][16,25,33,44,66,100,133] notation is also
1124                          allowed.
1125
1126                        * [no]ncq: Turn on or off NCQ.
1127
1128                        * nohrst, nosrst, norst: suppress hard, soft
1129                          and both resets.
1130
1131                        If there are multiple matching configurations changing
1132                        the same attribute, the last one is used.
1133
1134        lmb=debug       [KNL] Enable lmb debug messages.
1135
1136        load_ramdisk=   [RAM] List of ramdisks to load from floppy
1137                        See Documentation/blockdev/ramdisk.txt.
1138
1139        lockd.nlm_grace_period=P  [NFS] Assign grace period.
1140                        Format: <integer>
1141
1142        lockd.nlm_tcpport=N     [NFS] Assign TCP port.
1143                        Format: <integer>
1144
1145        lockd.nlm_timeout=T     [NFS] Assign timeout value.
1146                        Format: <integer>
1147
1148        lockd.nlm_udpport=M     [NFS] Assign UDP port.
1149                        Format: <integer>
1150
1151        logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
1152                        Format: <irq>
1153
1154        loglevel=       All Kernel Messages with a loglevel smaller than the
1155                        console loglevel will be printed to the console. It can
1156                        also be changed with klogd or other programs. The
1157                        loglevels are defined as follows:
1158
1159                        0 (KERN_EMERG)          system is unusable
1160                        1 (KERN_ALERT)          action must be taken immediately
1161                        2 (KERN_CRIT)           critical conditions
1162                        3 (KERN_ERR)            error conditions
1163                        4 (KERN_WARNING)        warning conditions
1164                        5 (KERN_NOTICE)         normal but significant condition
1165                        6 (KERN_INFO)           informational
1166                        7 (KERN_DEBUG)          debug-level messages
1167
1168        log_buf_len=n   Sets the size of the printk ring buffer, in bytes.
1169                        Format: { n | nk | nM }
1170                        n must be a power of two.  The default size
1171                        is set in the kernel config file.
1172
1173        logo.nologo     [FB] Disables display of the built-in Linux logo.
1174                        This may be used to provide more screen space for
1175                        kernel log messages and is useful when debugging
1176                        kernel boot problems.
1177
1178        lp=0            [LP]    Specify parallel ports to use, e.g,
1179        lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
1180        lp=reset                first parallel port). 'lp=0' disables the
1181        lp=auto                 printer driver. 'lp=reset' (which can be
1182                                specified in addition to the ports) causes
1183                                attached printers to be reset. Using
1184                                lp=port1,port2,... specifies the parallel ports
1185                                to associate lp devices with, starting with
1186                                lp0. A port specification may be 'none' to skip
1187                                that lp device, or a parport name such as
1188                                'parport0'. Specifying 'lp=auto' instead of a
1189                                port specification list means that device IDs
1190                                from each port should be examined, to see if
1191                                an IEEE 1284-compliant printer is attached; if
1192                                so, the driver will manage that printer.
1193                                See also header of drivers/char/lp.c.
1194
1195        lpj=n           [KNL]
1196                        Sets loops_per_jiffy to given constant, thus avoiding
1197                        time-consuming boot-time autodetection (up to 250 ms per
1198                        CPU). 0 enables autodetection (default). To determine
1199                        the correct value for your kernel, boot with normal
1200                        autodetection and see what value is printed. Note that
1201                        on SMP systems the preset will be applied to all CPUs,
1202                        which is likely to cause problems if your CPUs need
1203                        significantly divergent settings. An incorrect value
1204                        will cause delays in the kernel to be wrong, leading to
1205                        unpredictable I/O errors and other breakage. Although
1206                        unlikely, in the extreme case this might damage your
1207                        hardware.
1208
1209        ltpc=           [NET]
1210                        Format: <io>,<irq>,<dma>
1211
1212        mac5380=        [HW,SCSI] Format:
1213                        <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1214
1215        machvec=        [IA64] Force the use of a particular machine-vector
1216                        (machvec) in a generic kernel.
1217                        Example: machvec=hpzx1_swiotlb
1218
1219        max_loop=       [LOOP] Maximum number of loopback devices that can
1220                        be mounted
1221                        Format: <1-256>
1222
1223        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
1224                        should make use of.  maxcpus=n : n >= 0 limits the
1225                        kernel to using 'n' processors.  n=0 is a special case,
1226                        it is equivalent to "nosmp", which also disables
1227                        the IO APIC.
1228
1229        max_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory greater than
1230                        or equal to this physical address is ignored.
1231
1232        max_luns=       [SCSI] Maximum number of LUNs to probe.
1233                        Should be between 1 and 2^32-1.
1234
1235        max_report_luns=
1236                        [SCSI] Maximum number of LUNs received.
1237                        Should be between 1 and 16384.
1238
1239        mcatest=        [IA-64]
1240
1241        mce             [X86-32] Machine Check Exception
1242
1243        mce=option      [X86-64] See Documentation/x86/x86_64/boot-options.txt
1244
1245        md=             [HW] RAID subsystems devices and level
1246                        See Documentation/md.txt.
1247
1248        mdacon=         [MDA]
1249                        Format: <first>,<last>
1250                        Specifies range of consoles to be captured by the MDA.
1251
1252        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
1253                        Amount of memory to be used when the kernel is not able
1254                        to see the whole system memory or for test.
1255                        [X86-32] Use together with memmap= to avoid physical
1256                        address space collisions. Without memmap= PCI devices
1257                        could be placed at addresses belonging to unused RAM.
1258
1259        mem=nopentium   [BUGS=X86-32] Disable usage of 4MB pages for kernel
1260                        memory.
1261
1262        memchunk=nn[KMG]
1263                        [KNL,SH] Allow user to override the default size for
1264                        per-device physically contiguous DMA buffers.
1265
1266        memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1267                        E820 memory map, as specified by the user.
1268                        Such memmap=exactmap lines can be constructed based on
1269                        BIOS output or other requirements. See the memmap=nn@ss
1270                        option description.
1271
1272        memmap=nn[KMG]@ss[KMG]
1273                        [KNL] Force usage of a specific region of memory
1274                        Region of memory to be used, from ss to ss+nn.
1275
1276        memmap=nn[KMG]#ss[KMG]
1277                        [KNL,ACPI] Mark specific memory as ACPI data.
1278                        Region of memory to be used, from ss to ss+nn.
1279
1280        memmap=nn[KMG]$ss[KMG]
1281                        [KNL,ACPI] Mark specific memory as reserved.
1282                        Region of memory to be used, from ss to ss+nn.
1283                        Example: Exclude memory from 0x18690000-0x1869ffff
1284                                 memmap=64K$0x18690000
1285                                 or
1286                                 memmap=0x10000$0x18690000
1287
1288        memory_corruption_check=0/1 [X86]
1289                        Some BIOSes seem to corrupt the first 64k of
1290                        memory when doing things like suspend/resume.
1291                        Setting this option will scan the memory
1292                        looking for corruption.  Enabling this will
1293                        both detect corruption and prevent the kernel
1294                        from using the memory being corrupted.
1295                        However, its intended as a diagnostic tool; if
1296                        repeatable BIOS-originated corruption always
1297                        affects the same memory, you can use memmap=
1298                        to prevent the kernel from using that memory.
1299
1300        memory_corruption_check_size=size [X86]
1301                        By default it checks for corruption in the low
1302                        64k, making this memory unavailable for normal
1303                        use.  Use this parameter to scan for
1304                        corruption in more or less memory.
1305
1306        memory_corruption_check_period=seconds [X86]
1307                        By default it checks for corruption every 60
1308                        seconds.  Use this parameter to check at some
1309                        other rate.  0 disables periodic checking.
1310
1311        memtest=        [KNL,X86] Enable memtest
1312                        Format: <integer>
1313                        range: 0,4 : pattern number
1314                        default : 0 <disable>
1315
1316        meye.*=         [HW] Set MotionEye Camera parameters
1317                        See Documentation/video4linux/meye.txt.
1318
1319        mfgpt_irq=      [IA-32] Specify the IRQ to use for the
1320                        Multi-Function General Purpose Timers on AMD Geode
1321                        platforms.
1322
1323        mfgptfix        [X86-32] Fix MFGPT timers on AMD Geode platforms when
1324                        the BIOS has incorrectly applied a workaround. TinyBIOS
1325                        version 0.98 is known to be affected, 0.99 fixes the
1326                        problem by letting the user disable the workaround.
1327
1328        mga=            [HW,DRM]
1329
1330        min_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory below this
1331                        physical address is ignored.
1332
1333        mminit_loglevel=
1334                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1335                        parameter allows control of the logging verbosity for
1336                        the additional memory initialisation checks. A value
1337                        of 0 disables mminit logging and a level of 4 will
1338                        log everything. Information is printed at KERN_DEBUG
1339                        so loglevel=8 may also need to be specified.
1340
1341        mousedev.tap_time=
1342                        [MOUSE] Maximum time between finger touching and
1343                        leaving touchpad surface for touch to be considered
1344                        a tap and be reported as a left button click (for
1345                        touchpads working in absolute mode only).
1346                        Format: <msecs>
1347        mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
1348                        reporting absolute coordinates, such as tablets
1349        mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
1350                        reporting absolute coordinates, such as tablets
1351
1352        mpu401=         [HW,OSS]
1353                        Format: <io>,<irq>
1354
1355        MTD_Partition=  [MTD]
1356                        Format: <name>,<region-number>,<size>,<offset>
1357
1358        MTD_Region=     [MTD] Format:
1359                        <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1360
1361        mtdparts=       [MTD]
1362                        See drivers/mtd/cmdlinepart.c.
1363
1364        mtdset=         [ARM]
1365                        ARM/S3C2412 JIVE boot control
1366
1367                        See arch/arm/mach-s3c2412/mach-jive.c
1368
1369        mtouchusb.raw_coordinates=
1370                        [HW] Make the MicroTouch USB driver use raw coordinates
1371                        ('y', default) or cooked coordinates ('n')
1372
1373        n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card
1374
1375        NCR_D700=       [HW,SCSI]
1376                        See header of drivers/scsi/NCR_D700.c.
1377
1378        ncr5380=        [HW,SCSI]
1379
1380        ncr53c400=      [HW,SCSI]
1381
1382        ncr53c400a=     [HW,SCSI]
1383
1384        ncr53c406a=     [HW,SCSI]
1385
1386        ncr53c8xx=      [HW,SCSI]
1387
1388        netdev=         [NET] Network devices parameters
1389                        Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1390                        Note that mem_start is often overloaded to mean
1391                        something different and driver-specific.
1392                        This usage is only documented in each driver source
1393                        file if at all.
1394
1395        nf_conntrack.acct=
1396                        [NETFILTER] Enable connection tracking flow accounting
1397                        0 to disable accounting
1398                        1 to enable accounting
1399                        Default value depends on CONFIG_NF_CT_ACCT that is
1400                        going to be removed in 2.6.29.
1401
1402        nfsaddrs=       [NFS]
1403                        See Documentation/filesystems/nfsroot.txt.
1404
1405        nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
1406                        See Documentation/filesystems/nfsroot.txt.
1407
1408        nfs.callback_tcpport=
1409                        [NFS] set the TCP port on which the NFSv4 callback
1410                        channel should listen.
1411
1412        nfs.idmap_cache_timeout=
1413                        [NFS] set the maximum lifetime for idmapper cache
1414                        entries.
1415
1416        nfs.enable_ino64=
1417                        [NFS] enable 64-bit inode numbers.
1418                        If zero, the NFS client will fake up a 32-bit inode
1419                        number for the readdir() and stat() syscalls instead
1420                        of returning the full 64-bit number.
1421                        The default is to return 64-bit inode numbers.
1422
1423        nmi_debug=      [KNL,AVR32] Specify one or more actions to take
1424                        when a NMI is triggered.
1425                        Format: [state][,regs][,debounce][,die]
1426
1427        nmi_watchdog=   [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels
1428                        Format: [panic,][num]
1429                        Valid num: 0,1,2
1430                        0 - turn nmi_watchdog off
1431                        1 - use the IO-APIC timer for the NMI watchdog
1432                        2 - use the local APIC for the NMI watchdog using
1433                        a performance counter. Note: This will use one performance
1434                        counter and the local APIC's performance vector.
1435                        When panic is specified panic when an NMI watchdog timeout occurs.
1436                        This is useful when you use a panic=... timeout and need the box
1437                        quickly up again.
1438                        Instead of 1 and 2 it is possible to use the following
1439                        symbolic names: lapic and ioapic
1440                        Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1441
1442        no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
1443                        emulation library even if a 387 maths coprocessor
1444                        is present.
1445
1446        noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
1447                        caches in the slab allocator.  Saves per-node memory,
1448                        but will impact performance.
1449
1450        noalign         [KNL,ARM]
1451
1452        noapic          [SMP,APIC] Tells the kernel to not make use of any
1453                        IOAPICs that may be present in the system.
1454
1455        nobats          [PPC] Do not use BATs for mapping kernel lowmem
1456                        on "Classic" PPC cores.
1457
1458        nocache         [ARM]
1459
1460        nodelayacct     [KNL] Disable per-task delay accounting
1461
1462        nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.
1463
1464        nodsp           [SH] Disable hardware DSP at boot time.
1465
1466        noefi           [X86-32,X86-64] Disable EFI runtime services support.
1467
1468        noexec          [IA-64]
1469
1470        noexec          [X86-32,X86-64]
1471                        On X86-32 available only on PAE configured kernels.
1472                        noexec=on: enable non-executable mappings (default)
1473                        noexec=off: disable non-executable mappings
1474
1475        noexec32        [X86-64]
1476                        This affects only 32-bit executables.
1477                        noexec32=on: enable non-executable mappings (default)
1478                                read doesn't imply executable mappings
1479                        noexec32=off: disable non-executable mappings
1480                                read implies executable mappings
1481
1482        nofpu           [SH] Disable hardware FPU at boot time.
1483
1484        nofxsr          [BUGS=X86-32] Disables x86 floating point extended
1485                        register save and restore. The kernel will only save
1486                        legacy floating-point registers on task switch.
1487
1488        noclflush       [BUGS=X86] Don't use the CLFLUSH instruction
1489
1490        nohlt           [BUGS=ARM,SH]
1491
1492        no-hlt          [BUGS=X86-32] Tells the kernel that the hlt
1493                        instruction doesn't work correctly and not to
1494                        use it.
1495
1496        no_file_caps    Tells the kernel not to honor file capabilities.  The
1497                        only way then for a file to be executed with privilege
1498                        is to be setuid root or executed by root.
1499
1500        nohalt          [IA-64] Tells the kernel not to use the power saving
1501                        function PAL_HALT_LIGHT when idle. This increases
1502                        power-consumption. On the positive side, it reduces
1503                        interrupt wake-up latency, which may improve performance
1504                        in certain environments such as networked servers or
1505                        real-time systems.
1506
1507        nohz=           [KNL] Boottime enable/disable dynamic ticks
1508                        Valid arguments: on, off
1509                        Default: on
1510
1511        noirqdebug      [X86-32] Disables the code which attempts to detect and
1512                        disable unhandled interrupt sources.
1513
1514        no_timer_check  [X86-32,X86_64,APIC] Disables the code which tests for
1515                        broken timer IRQ sources.
1516
1517        noisapnp        [ISAPNP] Disables ISA PnP code.
1518
1519        noinitrd        [RAM] Tells the kernel not to load any configured
1520                        initial RAM disk.
1521
1522        nointroute      [IA-64]
1523
1524        nojitter        [IA64] Disables jitter checking for ITC timers.
1525
1526        nolapic         [X86-32,APIC] Do not enable or use the local APIC.
1527
1528        nolapic_timer   [X86-32,APIC] Do not use the local APIC timer.
1529
1530        nox2apic        [X86-64,APIC] Do not enable x2APIC mode.
1531
1532        x2apic_phys     [X86-64,APIC] Use x2apic physical mode instead of
1533                        default x2apic cluster mode on platforms
1534                        supporting x2apic.
1535
1536        noltlbs         [PPC] Do not use large page/tlb entries for kernel
1537                        lowmem mapping on PPC40x.
1538
1539        nomca           [IA-64] Disable machine check abort handling
1540
1541        nomce           [X86-32] Machine Check Exception
1542
1543        nomfgpt         [X86-32] Disable Multi-Function General Purpose
1544                        Timer usage (for AMD Geode machines).
1545
1546        noreplace-paravirt      [X86-32,PV_OPS] Don't patch paravirt_ops
1547
1548        noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
1549                        with UP alternatives
1550
1551        noresidual      [PPC] Don't use residual data on PReP machines.
1552
1553        noresume        [SWSUSP] Disables resume and restores original swap
1554                        space.
1555
1556        no-scroll       [VGA] Disables scrollback.
1557                        This is required for the Braillex ib80-piezo Braille
1558                        reader made by F.H. Papenmeier (Germany).
1559
1560        nosbagart       [IA-64]
1561
1562        nosep           [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1563
1564        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
1565                        and disable the IO APIC.  legacy for "maxcpus=0".
1566
1567        nosoftlockup    [KNL] Disable the soft-lockup detector.
1568
1569        noswapaccount   [KNL] Disable accounting of swap in memory resource
1570                        controller. (See Documentation/controllers/memory.txt)
1571
1572        nosync          [HW,M68K] Disables sync negotiation for all devices.
1573
1574        notsc           [BUGS=X86-32] Disable Time Stamp Counter
1575
1576        nousb           [USB] Disable the USB subsystem
1577
1578        nowb            [ARM]
1579
1580        nptcg=          [IA64] Override max number of concurrent global TLB
1581                        purges which is reported from either PAL_VM_SUMMARY or
1582                        SAL PALO.
1583
1584        numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1585                        one of ['zone', 'node', 'default'] can be specified
1586                        This can be set from sysctl after boot.
1587                        See Documentation/sysctl/vm.txt for details.
1588
1589        nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
1590
1591        ohci1394_dma=early      [HW] enable debugging via the ohci1394 driver.
1592                        See Documentation/debugging-via-ohci1394.txt for more
1593                        info.
1594
1595        olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1596                        Rather than timing out after 20 ms if an EC
1597                        command is not properly ACKed, override the length
1598                        of the timeout.  We have interrupts disabled while
1599                        waiting for the ACK, so if this is set too high
1600                        interrupts *may* be lost!
1601
1602        opl3=           [HW,OSS]
1603                        Format: <io>
1604
1605        oprofile.timer= [HW]
1606                        Use timer interrupt instead of performance counters
1607
1608        osst=           [HW,SCSI] SCSI Tape Driver
1609                        Format: <buffer_size>,<write_threshold>
1610                        See also Documentation/scsi/st.txt.
1611
1612        panic=          [KNL] Kernel behaviour on panic
1613                        Format: <timeout>
1614
1615        parkbd.port=    [HW] Parallel port number the keyboard adapter is
1616                        connected to, default is 0.
1617                        Format: <parport#>
1618        parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
1619                        0 for XT, 1 for AT (default is AT).
1620                        Format: <mode>
1621
1622        parport=        [HW,PPT] Specify parallel ports. 0 disables.
1623                        Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1624                        Use 'auto' to force the driver to use any
1625                        IRQ/DMA settings detected (the default is to
1626                        ignore detected IRQ/DMA settings because of
1627                        possible conflicts). You can specify the base
1628                        address, IRQ, and DMA settings; IRQ and DMA
1629                        should be numbers, or 'auto' (for using detected
1630                        settings on that particular port), or 'nofifo'
1631                        (to avoid using a FIFO even if it is detected).
1632                        Parallel ports are assigned in the order they
1633                        are specified on the command line, starting
1634                        with parport0.
1635
1636        parport_init_mode=      [HW,PPT]
1637                        Configure VIA parallel port to operate in
1638                        a specific mode. This is necessary on Pegasos
1639                        computer where firmware has no options for setting
1640                        up parallel port mode and sets it to spp.
1641                        Currently this function knows 686a and 8231 chips.
1642                        Format: [spp|ps2|epp|ecp|ecpepp]
1643
1644        pas2=           [HW,OSS] Format:
1645                        <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1646
1647        pas16=          [HW,SCSI]
1648                        See header of drivers/scsi/pas16.c.
1649
1650        pause_on_oops=
1651                        Halt all CPUs after the first oops has been printed for
1652                        the specified number of seconds.  This is to be used if
1653                        your oopses keep scrolling off the screen.
1654
1655        pcbit=          [HW,ISDN]
1656
1657        pcd.            [PARIDE]
1658                        See header of drivers/block/paride/pcd.c.
1659                        See also Documentation/blockdev/paride.txt.
1660
1661        pci=option[,option...]  [PCI] various PCI subsystem options:
1662                off             [X86] don't probe for the PCI bus
1663                bios            [X86-32] force use of PCI BIOS, don't access
1664                                the hardware directly. Use this if your machine
1665                                has a non-standard PCI host bridge.
1666                nobios          [X86-32] disallow use of PCI BIOS, only direct
1667                                hardware access methods are allowed. Use this
1668                                if you experience crashes upon bootup and you
1669                                suspect they are caused by the BIOS.
1670                conf1           [X86] Force use of PCI Configuration
1671                                Mechanism 1.
1672                conf2           [X86] Force use of PCI Configuration
1673                                Mechanism 2.
1674                noaer           [PCIE] If the PCIEAER kernel config parameter is
1675                                enabled, this kernel boot option can be used to
1676                                disable the use of PCIE advanced error reporting.
1677                nodomains       [PCI] Disable support for multiple PCI
1678                                root domains (aka PCI segments, in ACPI-speak).
1679                nommconf        [X86-32,X86_64] Disable use of MMCONFIG for PCI
1680                                Configuration
1681                nomsi           [MSI] If the PCI_MSI kernel config parameter is
1682                                enabled, this kernel boot option can be used to
1683                                disable the use of MSI interrupts system-wide.
1684                noioapicquirk   [APIC] Disable all boot interrupt quirks.
1685                                Safety option to keep boot IRQs enabled. This
1686                                should never be necessary.
1687                ioapicreroute   [APIC] Enable rerouting of boot IRQs to the
1688                                primary IO-APIC for bridges that cannot disable
1689                                boot IRQs. This fixes a source of spurious IRQs
1690                                when the system masks IRQs.
1691                noioapicreroute [APIC] Disable workaround that uses the
1692                                boot IRQ equivalent of an IRQ that connects to
1693                                a chipset where boot IRQs cannot be disabled.
1694                                The opposite of ioapicreroute.
1695                biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
1696                                routing table. These calls are known to be buggy
1697                                on several machines and they hang the machine
1698                                when used, but on other computers it's the only
1699                                way to get the interrupt routing table. Try
1700                                this option if the kernel is unable to allocate
1701                                IRQs or discover secondary PCI buses on your
1702                                motherboard.
1703                rom             [X86] Assign address space to expansion ROMs.
1704                                Use with caution as certain devices share
1705                                address decoders between ROMs and other
1706                                resources.
1707                norom           [X86] Do not assign address space to
1708                                expansion ROMs that do not already have
1709                                BIOS assigned address ranges.
1710                irqmask=0xMMMM  [X86] Set a bit mask of IRQs allowed to be
1711                                assigned automatically to PCI devices. You can
1712                                make the kernel exclude IRQs of your ISA cards
1713                                this way.
1714                pirqaddr=0xAAAAA        [X86] Specify the physical address
1715                                of the PIRQ table (normally generated
1716                                by the BIOS) if it is outside the
1717                                F0000h-100000h range.
1718                lastbus=N       [X86] Scan all buses thru bus #N. Can be
1719                                useful if the kernel is unable to find your
1720                                secondary buses and you want to tell it
1721                                explicitly which ones they are.
1722                assign-busses   [X86] Always assign all PCI bus
1723                                numbers ourselves, overriding
1724                                whatever the firmware may have done.
1725                usepirqmask     [X86] Honor the possible IRQ mask stored
1726                                in the BIOS $PIR table. This is needed on
1727                                some systems with broken BIOSes, notably
1728                                some HP Pavilion N5400 and Omnibook XE3
1729                                notebooks. This will have no effect if ACPI
1730                                IRQ routing is enabled.
1731                noacpi          [X86] Do not use ACPI for IRQ routing
1732                                or for PCI scanning.
1733                use_crs         [X86] Use _CRS for PCI resource
1734                                allocation.
1735                routeirq        Do IRQ routing for all PCI devices.
1736                                This is normally done in pci_enable_device(),
1737                                so this option is a temporary workaround
1738                                for broken drivers that don't call it.
1739                skip_isa_align  [X86] do not align io start addr, so can
1740                                handle more pci cards
1741                firmware        [ARM] Do not re-enumerate the bus but instead
1742                                just use the configuration from the
1743                                bootloader. This is currently used on
1744                                IXP2000 systems where the bus has to be
1745                                configured a certain way for adjunct CPUs.
1746                noearly         [X86] Don't do any early type 1 scanning.
1747                                This might help on some broken boards which
1748                                machine check when some devices' config space
1749                                is read. But various workarounds are disabled
1750                                and some IOMMU drivers will not work.
1751                bfsort          Sort PCI devices into breadth-first order.
1752                                This sorting is done to get a device
1753                                order compatible with older (<= 2.4) kernels.
1754                nobfsort        Don't sort PCI devices into breadth-first order.
1755                cbiosize=nn[KMG]        The fixed amount of bus space which is
1756                                reserved for the CardBus bridge's IO window.
1757                                The default value is 256 bytes.
1758                cbmemsize=nn[KMG]       The fixed amount of bus space which is
1759                                reserved for the CardBus bridge's memory
1760                                window. The default value is 64 megabytes.
1761
1762        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
1763                        Management.
1764                off     Disable ASPM.
1765                force   Enable ASPM even on devices that claim not to support it.
1766                        WARNING: Forcing ASPM on may cause system lockups.
1767
1768        pcmv=           [HW,PCMCIA] BadgePAD 4
1769
1770        pd.             [PARIDE]
1771                        See Documentation/blockdev/paride.txt.
1772
1773        pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1774                        boot time.
1775                        Format: { 0 | 1 }
1776                        See arch/parisc/kernel/pdc_chassis.c
1777
1778        pf.             [PARIDE]
1779                        See Documentation/blockdev/paride.txt.
1780
1781        pg.             [PARIDE]
1782                        See Documentation/blockdev/paride.txt.
1783
1784        pirq=           [SMP,APIC] Manual mp-table setup
1785                        See Documentation/x86/i386/IO-APIC.txt.
1786
1787        plip=           [PPT,NET] Parallel port network link
1788                        Format: { parport<nr> | timid | 0 }
1789                        See also Documentation/parport.txt.
1790
1791        pmtmr=          [X86] Manual setup of pmtmr I/O Port. 
1792                        Override pmtimer IOPort with a hex value.
1793                        e.g. pmtmr=0x508
1794
1795        pnp.debug       [PNP]
1796                        Enable PNP debug messages.  This depends on the
1797                        CONFIG_PNP_DEBUG_MESSAGES option.
1798
1799        pnpacpi=        [ACPI]
1800                        { off }
1801
1802        pnpbios=        [ISAPNP]
1803                        { on | off | curr | res | no-curr | no-res }
1804
1805        pnp_reserve_irq=
1806                        [ISAPNP] Exclude IRQs for the autoconfiguration
1807
1808        pnp_reserve_dma=
1809                        [ISAPNP] Exclude DMAs for the autoconfiguration
1810
1811        pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1812                        Ranges are in pairs (I/O port base and size).
1813
1814        pnp_reserve_mem=
1815                        [ISAPNP] Exclude memory regions for the
1816                        autoconfiguration.
1817                        Ranges are in pairs (memory base and size).
1818
1819        dynamic_printk  Enables pr_debug()/dev_dbg() calls if
1820                        CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
1821                        These can also be switched on/off via
1822                        <debugfs>/dynamic_printk/modules
1823
1824        print-fatal-signals=
1825                        [KNL] debug: print fatal signals
1826                        print-fatal-signals=1: print segfault info to
1827                        the kernel console.
1828                        default: off.
1829
1830        printk.time=    Show timing data prefixed to each printk message line
1831                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
1832
1833        profile=        [KNL] Enable kernel profiling via /proc/profile
1834                        Format: [schedule,]<number>
1835                        Param: "schedule" - profile schedule points.
1836                        Param: <number> - step/bucket size as a power of 2 for
1837                                statistical time based profiling.
1838                        Param: "sleep" - profile D-state sleeping (millisecs).
1839                                Requires CONFIG_SCHEDSTATS
1840                        Param: "kvm" - profile VM exits.
1841
1842        processor.max_cstate=   [HW,ACPI]
1843                        Limit processor to maximum C-state
1844                        max_cstate=9 overrides any DMI blacklist limit.
1845
1846        processor.nocst [HW,ACPI]
1847                        Ignore the _CST method to determine C-states,
1848                        instead using the legacy FADT method
1849
1850        prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1851                        before loading.
1852                        See Documentation/blockdev/ramdisk.txt.
1853
1854        psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
1855                        probe for; one of (bare|imps|exps|lifebook|any).
1856        psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
1857                        per second.
1858        psmouse.resetafter=     [HW,MOUSE]
1859                        Try to reset the device after so many bad packets
1860                        (0 = never).
1861        psmouse.resolution=
1862                        [HW,MOUSE] Set desired mouse resolution, in dpi.
1863        psmouse.smartscroll=
1864                        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1865                        0 = disabled, 1 = enabled (default).
1866
1867        pss=            [HW,OSS] Personal Sound System (ECHO ESC614)
1868                        Format:
1869                        <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1870
1871        pt.             [PARIDE]
1872                        See Documentation/blockdev/paride.txt.
1873
1874        pty.legacy_count=
1875                        [KNL] Number of legacy pty's. Overwrites compiled-in
1876                        default number.
1877
1878        quiet           [KNL] Disable most log messages
1879
1880        r128=           [HW,DRM]
1881
1882        raid=           [HW,RAID]
1883                        See Documentation/md.txt.
1884
1885        ramdisk_blocksize=      [RAM]
1886                        See Documentation/blockdev/ramdisk.txt.
1887
1888        ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
1889                        See Documentation/blockdev/ramdisk.txt.
1890
1891        rcupdate.blimit=        [KNL,BOOT]
1892                        Set maximum number of finished RCU callbacks to process
1893                        in one batch.
1894
1895        rcupdate.qhimark=       [KNL,BOOT]
1896                        Set threshold of queued
1897                        RCU callbacks over which batch limiting is disabled.
1898
1899        rcupdate.qlowmark=      [KNL,BOOT]
1900                        Set threshold of queued RCU callbacks below which
1901                        batch limiting is re-enabled.
1902
1903        rdinit=         [KNL]
1904                        Format: <full_path>
1905                        Run specified binary instead of /init from the ramdisk,
1906                        used for early userspace startup. See initrd.
1907
1908        reboot=         [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1909                        Format: <reboot_mode>[,<reboot_mode2>[,...]]
1910                        See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1911
1912        relax_domain_level=
1913                        [KNL, SMP] Set scheduler's default relax_domain_level.
1914                        See Documentation/cpusets.txt.
1915
1916        reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area
1917
1918        reservetop=     [X86-32]
1919                        Format: nn[KMG]
1920                        Reserves a hole at the top of the kernel virtual
1921                        address space.
1922
1923        reset_devices   [KNL] Force drivers to reset the underlying device
1924                        during initialization.
1925
1926        resume=         [SWSUSP]
1927                        Specify the partition device for software suspend
1928
1929        resume_offset=  [SWSUSP]
1930                        Specify the offset from the beginning of the partition
1931                        given by "resume=" at which the swap header is located,
1932                        in <PAGE_SIZE> units (needed only for swap files).
1933                        See  Documentation/power/swsusp-and-swap-files.txt
1934
1935        retain_initrd   [RAM] Keep initrd memory after extraction
1936
1937        rhash_entries=  [KNL,NET]
1938                        Set number of hash buckets for route cache
1939
1940        riscom8=        [HW,SERIAL]
1941                        Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1942
1943        ro              [KNL] Mount root device read-only on boot
1944
1945        root=           [KNL] Root filesystem
1946
1947        rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
1948                        mount the root filesystem
1949
1950        rootflags=      [KNL] Set root filesystem mount option string
1951
1952        rootfstype=     [KNL] Set root filesystem type
1953
1954        rootwait        [KNL] Wait (indefinitely) for root device to show up.
1955                        Useful for devices that are detected asynchronously
1956                        (e.g. USB and MMC devices).
1957
1958        root_plug.vendor_id=
1959                        [ROOTPLUG] Override the default vendor ID
1960
1961        root_plug.product_id=
1962                        [ROOTPLUG] Override the default product ID
1963
1964        root_plug.debug=
1965                        [ROOTPLUG] Enable debugging output
1966
1967        rw              [KNL] Mount root device read-write on boot
1968
1969        S               [KNL] Run init in single mode
1970
1971        sa1100ir        [NET]
1972                        See drivers/net/irda/sa1100_ir.c.
1973
1974        sbni=           [NET] Granch SBNI12 leased line adapter
1975
1976        sc1200wdt=      [HW,WDT] SC1200 WDT (watchdog) driver
1977                        Format: <io>[,<timeout>[,<isapnp>]]
1978
1979        scsi_debug_*=   [SCSI]
1980                        See drivers/scsi/scsi_debug.c.
1981
1982        scsi_default_dev_flags=
1983                        [SCSI] SCSI default device flags
1984                        Format: <integer>
1985
1986        scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1987                        Format: <vendor>:<model>:<flags>
1988                        (flags are integer value)
1989
1990        scsi_logging_level=     [SCSI] a bit mask of logging levels
1991                        See drivers/scsi/scsi_logging.h for bits.  Also
1992                        settable via sysctl at dev.scsi.logging_level
1993                        (/proc/sys/dev/scsi/logging_level).
1994                        There is also a nice 'scsi_logging_level' script in the
1995                        S390-tools package, available for download at
1996                        http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1997
1998        scsi_mod.scan=  [SCSI] sync (default) scans SCSI busses as they are
1999                        discovered.  async scans them in kernel threads,
2000                        allowing boot to proceed.  none ignores them, expecting
2001                        user space to do the scan.
2002
2003        selinux         [SELINUX] Disable or enable SELinux at boot time.
2004                        Format: { "0" | "1" }
2005                        See security/selinux/Kconfig help text.
2006                        0 -- disable.
2007                        1 -- enable.
2008                        Default value is set via kernel config option.
2009                        If enabled at boot time, /selinux/disable can be used
2010                        later to disable prior to initial policy load.
2011
2012        selinux_compat_net =
2013                        [SELINUX] Set initial selinux_compat_net flag value.
2014                        Format: { "0" | "1" }
2015                        0 -- use new secmark-based packet controls
2016                        1 -- use legacy packet controls
2017                        Default value is 0 (preferred).
2018                        Value can be changed at runtime via
2019                        /selinux/compat_net.
2020
2021        serialnumber    [BUGS=X86-32]
2022
2023        shapers=        [NET]
2024                        Maximal number of shapers.
2025
2026        show_msr=       [x86] show boot-time MSR settings
2027                        Format: { <integer> }
2028                        Show boot-time (BIOS-initialized) MSR settings.
2029                        The parameter means the number of CPUs to show,
2030                        for example 1 means boot CPU only.
2031
2032        sim710=         [SCSI,HW]
2033                        See header of drivers/scsi/sim710.c.
2034
2035        simeth=         [IA-64]
2036        simscsi=
2037
2038        slram=          [HW,MTD]
2039
2040        slub_debug[=options[,slabs]]    [MM, SLUB]
2041                        Enabling slub_debug allows one to determine the
2042                        culprit if slab objects become corrupted. Enabling
2043                        slub_debug can create guard zones around objects and
2044                        may poison objects when not in use. Also tracks the
2045                        last alloc / free. For more information see
2046                        Documentation/vm/slub.txt.
2047
2048        slub_max_order= [MM, SLUB]
2049                        Determines the maximum allowed order for slabs.
2050                        A high setting may cause OOMs due to memory
2051                        fragmentation. For more information see
2052                        Documentation/vm/slub.txt.
2053
2054        slub_min_objects=       [MM, SLUB]
2055                        The minimum number of objects per slab. SLUB will
2056                        increase the slab order up to slub_max_order to
2057                        generate a sufficiently large slab able to contain
2058                        the number of objects indicated. The higher the number
2059                        of objects the smaller the overhead of tracking slabs
2060                        and the less frequently locks need to be acquired.
2061                        For more information see Documentation/vm/slub.txt.
2062
2063        slub_min_order= [MM, SLUB]
2064                        Determines the mininum page order for slabs. Must be
2065                        lower than slub_max_order.
2066                        For more information see Documentation/vm/slub.txt.
2067
2068        slub_nomerge    [MM, SLUB]
2069                        Disable merging of slabs with similar size. May be
2070                        necessary if there is some reason to distinguish
2071                        allocs to different slabs. Debug options disable
2072                        merging on their own.
2073                        For more information see Documentation/vm/slub.txt.
2074
2075        smart2=         [HW]
2076                        Format: <io1>[,<io2>[,...,<io8>]]
2077
2078        smp-alt-once    [X86-32,SMP] On a hotplug CPU system, only
2079                        attempt to substitute SMP alternatives once at boot.
2080
2081        smsc-ircc2.nopnp        [HW] Don't use PNP to discover SMC devices
2082        smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
2083        smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
2084        smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
2085        smsc-ircc2.ircc_irq=    [HW] IRQ line
2086        smsc-ircc2.ircc_dma=    [HW] DMA channel
2087        smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2088                                0: Toshiba Satellite 1800 (GP data pin select)
2089                                1: Fast pin select (default)
2090                                2: ATC IRMode
2091
2092        snd-ad1816a=    [HW,ALSA]
2093
2094        snd-ad1848=     [HW,ALSA]
2095
2096        snd-ali5451=    [HW,ALSA]
2097
2098        snd-als100=     [HW,ALSA]
2099
2100        snd-als4000=    [HW,ALSA]
2101
2102        snd-azt2320=    [HW,ALSA]
2103
2104        snd-cmi8330=    [HW,ALSA]
2105
2106        snd-cmipci=     [HW,ALSA]
2107
2108        snd-cs4231=     [HW,ALSA]
2109
2110        snd-cs4232=     [HW,ALSA]
2111
2112        snd-cs4236=     [HW,ALSA]
2113
2114        snd-cs4281=     [HW,ALSA]
2115
2116        snd-cs46xx=     [HW,ALSA]
2117
2118        snd-dt019x=     [HW,ALSA]
2119
2120        snd-dummy=      [HW,ALSA]
2121
2122        snd-emu10k1=    [HW,ALSA]
2123
2124        snd-ens1370=    [HW,ALSA]
2125
2126        snd-ens1371=    [HW,ALSA]
2127
2128        snd-es968=      [HW,ALSA]
2129
2130        snd-es1688=     [HW,ALSA]
2131
2132        snd-es18xx=     [HW,ALSA]
2133
2134        snd-es1938=     [HW,ALSA]
2135
2136        snd-es1968=     [HW,ALSA]
2137
2138        snd-fm801=      [HW,ALSA]
2139
2140        snd-gusclassic= [HW,ALSA]
2141
2142        snd-gusextreme= [HW,ALSA]
2143
2144        snd-gusmax=     [HW,ALSA]
2145
2146        snd-hdsp=       [HW,ALSA]
2147
2148        snd-ice1712=    [HW,ALSA]
2149
2150        snd-intel8x0=   [HW,ALSA]
2151
2152        snd-interwave=  [HW,ALSA]
2153
2154        snd-interwave-stb=
2155                        [HW,ALSA]
2156
2157        snd-korg1212=   [HW,ALSA]
2158
2159        snd-maestro3=   [HW,ALSA]
2160
2161        snd-mpu401=     [HW,ALSA]
2162
2163        snd-mtpav=      [HW,ALSA]
2164
2165        snd-nm256=      [HW,ALSA]
2166
2167        snd-opl3sa2=    [HW,ALSA]
2168
2169        snd-opti92x-ad1848=
2170                        [HW,ALSA]
2171
2172        snd-opti92x-cs4231=
2173                        [HW,ALSA]
2174
2175        snd-opti93x=    [HW,ALSA]
2176
2177        snd-pmac=       [HW,ALSA]
2178
2179        snd-rme32=      [HW,ALSA]
2180
2181        snd-rme96=      [HW,ALSA]
2182
2183        snd-rme9652=    [HW,ALSA]
2184
2185        snd-sb8=        [HW,ALSA]
2186
2187        snd-sb16=       [HW,ALSA]
2188
2189        snd-sbawe=      [HW,ALSA]
2190
2191        snd-serial=     [HW,ALSA]
2192
2193        snd-sgalaxy=    [HW,ALSA]
2194
2195        snd-sonicvibes= [HW,ALSA]
2196
2197        snd-sun-amd7930=
2198                        [HW,ALSA]
2199
2200        snd-sun-cs4231= [HW,ALSA]
2201
2202        snd-trident=    [HW,ALSA]
2203
2204        snd-usb-audio=  [HW,ALSA,USB]
2205
2206        snd-via82xx=    [HW,ALSA]
2207
2208        snd-virmidi=    [HW,ALSA]
2209
2210        snd-wavefront=  [HW,ALSA]
2211
2212        snd-ymfpci=     [HW,ALSA]
2213
2214        softlockup_panic=
2215                        [KNL] Should the soft-lockup detector generate panics.
2216
2217        sonypi.*=       [HW] Sony Programmable I/O Control Device driver
2218                        See Documentation/sonypi.txt
2219
2220        specialix=      [HW,SERIAL] Specialix multi-serial port adapter
2221                        See Documentation/serial/specialix.txt.
2222
2223        spia_io_base=   [HW,MTD]
2224        spia_fio_base=
2225        spia_pedr=
2226        spia_peddr=
2227
2228        sscape=         [HW,OSS]
2229                        Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2230
2231        st=             [HW,SCSI] SCSI tape parameters (buffers, etc.)
2232                        See Documentation/scsi/st.txt.
2233
2234        stacktrace      [FTRACE]
2235                        Enabled the stack tracer on boot up.
2236
2237        sti=            [PARISC,HW]
2238                        Format: <num>
2239                        Set the STI (builtin display/keyboard on the HP-PARISC
2240                        machines) console (graphic card) which should be used
2241                        as the initial boot-console.
2242                        See also comment in drivers/video/console/sticore.c.
2243
2244        sti_font=       [HW]
2245                        See comment in drivers/video/console/sticore.c.
2246
2247        stifb=          [HW]
2248                        Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2249
2250        sunrpc.pool_mode=
2251                        [NFS]
2252                        Control how the NFS server code allocates CPUs to
2253                        service thread pools.  Depending on how many NICs
2254                        you have and where their interrupts are bound, this
2255                        option will affect which CPUs will do NFS serving.
2256                        Note: this parameter cannot be changed while the
2257                        NFS server is running.
2258
2259                        auto        the server chooses an appropriate mode
2260                                    automatically using heuristics
2261                        global      a single global pool contains all CPUs
2262                        percpu      one pool for each CPU
2263                        pernode     one pool for each NUMA node (equivalent
2264                                    to global on non-NUMA machines)
2265
2266        swiotlb=        [IA-64] Number of I/O TLB slabs
2267
2268        switches=       [HW,M68k]
2269
2270        sym53c416=      [HW,SCSI]
2271                        See header of drivers/scsi/sym53c416.c.
2272
2273        sysrq_always_enabled
2274                        [KNL]
2275                        Ignore sysrq setting - this boot parameter will
2276                        neutralize any effect of /proc/sys/kernel/sysrq.
2277                        Useful for debugging.
2278
2279        t128=           [HW,SCSI]
2280                        See header of drivers/scsi/t128.c.
2281
2282        tdfx=           [HW,DRM]
2283
2284        test_suspend=   [SUSPEND]
2285                        Specify "mem" (for Suspend-to-RAM) or "standby" (for
2286                        standby suspend) as the system sleep state to briefly
2287                        enter during system startup.  The system is woken from
2288                        this state using a wakeup-capable RTC alarm.
2289
2290        thash_entries=  [KNL,NET]
2291                        Set number of hash buckets for TCP connection
2292
2293        thermal.act=    [HW,ACPI]
2294                        -1: disable all active trip points in all thermal zones
2295                        <degrees C>: override all lowest active trip points
2296
2297        thermal.crt=    [HW,ACPI]
2298                        -1: disable all critical trip points in all thermal zones
2299                        <degrees C>: override all critical trip points
2300
2301        thermal.nocrt=  [HW,ACPI]
2302                        Set to disable actions on ACPI thermal zone
2303                        critical and hot trip points.
2304
2305        thermal.off=    [HW,ACPI]
2306                        1: disable ACPI thermal control
2307
2308        thermal.psv=    [HW,ACPI]
2309                        -1: disable all passive trip points
2310                        <degrees C>: override all passive trip points to this
2311                        value
2312
2313        thermal.tzp=    [HW,ACPI]
2314                        Specify global default ACPI thermal zone polling rate
2315                        <deci-seconds>: poll all this frequency
2316                        0: no polling (default)
2317
2318        tmscsim=        [HW,SCSI]
2319                        See comment before function dc390_setup() in
2320                        drivers/scsi/tmscsim.c.
2321
2322        topology=       [S390]
2323                        Format: {off | on}
2324                        Specify if the kernel should make use of the cpu
2325                        topology informations if the hardware supports these.
2326                        The scheduler will make use of these informations and
2327                        e.g. base its process migration decisions on it.
2328                        Default is off.
2329
2330        tp720=          [HW,PS2]
2331
2332        trix=           [HW,OSS] MediaTrix AudioTrix Pro
2333                        Format:
2334                        <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2335
2336        tsc=            Disable clocksource-must-verify flag for TSC.
2337                        Format: <string>
2338                        [x86] reliable: mark tsc clocksource as reliable, this
2339                        disables clocksource verification at runtime.
2340                        Used to enable high-resolution timer mode on older
2341                        hardware, and in virtualized environment.
2342
2343        turbografx.map[2|3]=    [HW,JOY]
2344                        TurboGraFX parallel port interface
2345                        Format:
2346                        <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2347                        See also Documentation/input/joystick-parport.txt
2348
2349        u14-34f=        [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2350                        See header of drivers/scsi/u14-34f.c.
2351
2352        uart401=        [HW,OSS]
2353                        Format: <io>,<irq>
2354
2355        uart6850=       [HW,OSS]
2356                        Format: <io>,<irq>
2357
2358        uhci-hcd.ignore_oc=
2359                        [USB] Ignore overcurrent events (default N).
2360                        Some badly-designed motherboards generate lots of
2361                        bogus events, for ports that aren't wired to
2362                        anything.  Set this parameter to avoid log spamming.
2363                        Note that genuine overcurrent events won't be
2364                        reported either.
2365
2366        unknown_nmi_panic
2367                        [X86-32,X86-64]
2368                        Set unknown_nmi_panic=1 early on boot.
2369
2370        usbcore.autosuspend=
2371                        [USB] The autosuspend time delay (in seconds) used
2372                        for newly-detected USB devices (default 2).  This
2373                        is the time required before an idle device will be
2374                        autosuspended.  Devices for which the delay is set
2375                        to a negative value won't be autosuspended at all.
2376
2377        usbcore.usbfs_snoop=
2378                        [USB] Set to log all usbfs traffic (default 0 = off).
2379
2380        usbcore.blinkenlights=
2381                        [USB] Set to cycle leds on hubs (default 0 = off).
2382
2383        usbcore.old_scheme_first=
2384                        [USB] Start with the old device initialization
2385                        scheme (default 0 = off).
2386
2387        usbcore.use_both_schemes=
2388                        [USB] Try the other device initialization scheme
2389                        if the first one fails (default 1 = enabled).
2390
2391        usbcore.initial_descriptor_timeout=
2392                        [USB] Specifies timeout for the initial 64-byte
2393                        USB_REQ_GET_DESCRIPTOR request in milliseconds
2394                        (default 5000 = 5.0 seconds).
2395
2396        usbhid.mousepoll=
2397                        [USBHID] The interval which mice are to be polled at.
2398
2399        usb-storage.delay_use=
2400                        [UMS] The delay in seconds before a new device is
2401                        scanned for Logical Units (default 5).
2402
2403        usb-storage.quirks=
2404                        [UMS] A list of quirks entries to supplement or
2405                        override the built-in unusual_devs list.  List
2406                        entries are separated by commas.  Each entry has
2407                        the form VID:PID:Flags where VID and PID are Vendor
2408                        and Product ID values (4-digit hex numbers) and
2409                        Flags is a set of characters, each corresponding
2410                        to a common usb-storage quirk flag as follows:
2411                                a = SANE_SENSE (collect more than 18 bytes
2412                                        of sense data);
2413                                c = FIX_CAPACITY (decrease the reported
2414                                        device capacity by one sector);
2415                                h = CAPACITY_HEURISTICS (decrease the
2416                                        reported device capacity by one
2417                                        sector if the number is odd);
2418                                i = IGNORE_DEVICE (don't bind to this
2419                                        device);
2420                                l = NOT_LOCKABLE (don't try to lock and
2421                                        unlock ejectable media);
2422                                m = MAX_SECTORS_64 (don't transfer more
2423                                        than 64 sectors = 32 KB at a time);
2424                                o = CAPACITY_OK (accept the capacity
2425                                        reported by the device);
2426                                r = IGNORE_RESIDUE (the device reports
2427                                        bogus residue values);
2428                                s = SINGLE_LUN (the device has only one
2429                                        Logical Unit);
2430                                w = NO_WP_DETECT (don't test whether the
2431                                        medium is write-protected).
2432                        Example: quirks=0419:aaf5:rl,0421:0433:rc
2433
2434        add_efi_memmap  [EFI; x86-32,X86-64] Include EFI memory map in
2435                        kernel's map of available physical RAM.
2436
2437        vdso=           [X86-32,SH,x86-64]
2438                        vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2439                        vdso=1: enable VDSO (default)
2440                        vdso=0: disable VDSO mapping
2441
2442        vdso32=         [X86-32,X86-64]
2443                        vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2444                        vdso32=1: enable 32-bit VDSO (default)
2445                        vdso32=0: disable 32-bit VDSO mapping
2446
2447        vector=         [IA-64,SMP]
2448                        vector=percpu: enable percpu vector domain
2449
2450        video=          [FB] Frame buffer configuration
2451                        See Documentation/fb/modedb.txt.
2452
2453        vga=            [BOOT,X86-32] Select a particular video mode
2454                        See Documentation/x86/boot.txt and
2455                        Documentation/svga.txt.
2456                        Use vga=ask for menu.
2457                        This is actually a boot loader parameter; the value is
2458                        passed to the kernel using a special protocol.
2459
2460        vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2461                        size of <nn>. This can be used to increase the
2462                        minimum size (128MB on x86). It can also be used to
2463                        decrease the size and leave more room for directly
2464                        mapped kernel RAM.
2465
2466        vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
2467                        Format: <command>
2468
2469        vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
2470                        Format: <command>
2471
2472        vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
2473                        Format: <command>
2474
2475        waveartist=     [HW,OSS]
2476                        Format: <io>,<irq>,<dma>,<dma2>
2477
2478        wd33c93=        [HW,SCSI]
2479                        See header of drivers/scsi/wd33c93.c.
2480
2481        wd7000=         [HW,SCSI]
2482                        See header of drivers/scsi/wd7000.c.
2483
2484        wdt=            [WDT] Watchdog
2485                        See Documentation/watchdog/wdt.txt.
2486
2487        xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2488        xd_geo=         See header of drivers/block/xd.c.
2489
2490        xirc2ps_cs=     [NET,PCMCIA]
2491                        Format:
2492                        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2493
2494        norandmaps      Don't use address space randomization.  Equivalent to
2495                        echo 0 > /proc/sys/kernel/randomize_va_space
2496
2497______________________________________________________________________
2498
2499TODO:
2500
2501        Add documentation for ALSA options.
2502        Add more DRM drivers.
2503