linux/Documentation/arm/Setup
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   1Kernel initialisation parameters on ARM Linux
   2---------------------------------------------
   3
   4The following document describes the kernel initialisation parameter
   5structure, otherwise known as 'struct param_struct' which is used
   6for most ARM Linux architectures.
   7
   8This structure is used to pass initialisation parameters from the
   9kernel loader to the Linux kernel proper, and may be short lived
  10through the kernel initialisation process.  As a general rule, it
  11should not be referenced outside of arch/arm/kernel/setup.c:setup_arch().
  12
  13There are a lot of parameters listed in there, and they are described
  14below:
  15
  16 page_size
  17
  18   This parameter must be set to the page size of the machine, and
  19   will be checked by the kernel.
  20
  21 nr_pages
  22
  23   This is the total number of pages of memory in the system.  If
  24   the memory is banked, then this should contain the total number
  25   of pages in the system.
  26
  27   If the system contains separate VRAM, this value should not
  28   include this information.
  29
  30 ramdisk_size
  31
  32   This is now obsolete, and should not be used.
  33
  34 flags
  35
  36   Various kernel flags, including:
  37    bit 0 - 1 = mount root read only
  38    bit 1 - unused
  39    bit 2 - 0 = load ramdisk
  40    bit 3 - 0 = prompt for ramdisk
  41
  42 rootdev
  43
  44   major/minor number pair of device to mount as the root filesystem.
  45
  46 video_num_cols
  47 video_num_rows
  48
  49   These two together describe the character size of the dummy console,
  50   or VGA console character size.  They should not be used for any other
  51   purpose.
  52
  53   It's generally a good idea to set these to be either standard VGA, or
  54   the equivalent character size of your fbcon display.  This then allows
  55   all the bootup messages to be displayed correctly.
  56
  57 video_x
  58 video_y
  59
  60   This describes the character position of cursor on VGA console, and
  61   is otherwise unused. (should not be used for other console types, and
  62   should not be used for other purposes).
  63
  64 memc_control_reg
  65
  66   MEMC chip control register for Acorn Archimedes and Acorn A5000
  67   based machines.  May be used differently by different architectures.
  68
  69 sounddefault
  70
  71   Default sound setting on Acorn machines.  May be used differently by
  72   different architectures.
  73
  74 adfsdrives
  75
  76   Number of ADFS/MFM disks.  May be used differently by different
  77   architectures.
  78
  79 bytes_per_char_h
  80 bytes_per_char_v
  81
  82   These are now obsolete, and should not be used.
  83
  84 pages_in_bank[4]
  85
  86   Number of pages in each bank of the systems memory (used for RiscPC).
  87   This is intended to be used on systems where the physical memory
  88   is non-contiguous from the processors point of view.
  89
  90 pages_in_vram
  91
  92   Number of pages in VRAM (used on Acorn RiscPC).  This value may also
  93   be used by loaders if the size of the video RAM can't be obtained
  94   from the hardware.
  95
  96 initrd_start
  97 initrd_size
  98
  99   This describes the kernel virtual start address and size of the
 100   initial ramdisk.
 101
 102 rd_start
 103
 104   Start address in sectors of the ramdisk image on a floppy disk.
 105
 106 system_rev
 107
 108   system revision number.
 109
 110 system_serial_low
 111 system_serial_high
 112
 113   system 64-bit serial number
 114
 115 mem_fclk_21285
 116
 117   The speed of the external oscillator to the 21285 (footbridge),
 118   which control's the speed of the memory bus, timer & serial port.
 119   Depending upon the speed of the cpu its value can be between
 120   0-66 MHz. If no params are passed or a value of zero is passed,
 121   then a value of 50 Mhz is the default on 21285 architectures.
 122
 123 paths[8][128]
 124
 125   These are now obsolete, and should not be used.
 126
 127 commandline
 128
 129   Kernel command line parameters.  Details can be found elsewhere.
 130
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