linux/Documentation/kbuild/kconfig.txt
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   1This file contains some assistance for using "make *config".
   2
   3Use "make help" to list all of the possible configuration targets.
   4
   5The xconfig ('qconf') and menuconfig ('mconf') programs also
   6have embedded help text.  Be sure to check it for navigation,
   7search, and other general help text.
   8
   9======================================================================
  10General
  11--------------------------------------------------
  12
  13New kernel releases often introduce new config symbols.  Often more
  14important, new kernel releases may rename config symbols.  When
  15this happens, using a previously working .config file and running
  16"make oldconfig" won't necessarily produce a working new kernel
  17for you, so you may find that you need to see what NEW kernel
  18symbols have been introduced.
  19
  20To see a list of new config symbols when using "make oldconfig", use
  21
  22        cp user/some/old.config .config
  23        yes "" | make oldconfig >conf.new
  24
  25and the config program will list as (NEW) any new symbols that have
  26unknown values.  Of course, the .config file is also updated with
  27new (default) values, so you can use:
  28
  29        grep "(NEW)" conf.new
  30
  31to see the new config symbols or you can use diffconfig to see the
  32differences between the previous and new .config files:
  33
  34        scripts/diffconfig .config.old .config | less
  35
  36______________________________________________________________________
  37Environment variables for '*config'
  38
  39KCONFIG_CONFIG
  40--------------------------------------------------
  41This environment variable can be used to specify a default kernel config
  42file name to override the default name of ".config".
  43
  44KCONFIG_OVERWRITECONFIG
  45--------------------------------------------------
  46If you set KCONFIG_OVERWRITECONFIG in the environment, Kconfig will not
  47break symlinks when .config is a symlink to somewhere else.
  48
  49CONFIG_
  50--------------------------------------------------
  51If you set CONFIG_ in the environment, Kconfig will prefix all symbols
  52with its value when saving the configuration, instead of using the default,
  53"CONFIG_".
  54
  55______________________________________________________________________
  56Environment variables for '{allyes/allmod/allno/rand}config'
  57
  58KCONFIG_ALLCONFIG
  59--------------------------------------------------
  60(partially based on lkml email from/by Rob Landley, re: miniconfig)
  61--------------------------------------------------
  62The allyesconfig/allmodconfig/allnoconfig/randconfig variants can also
  63use the environment variable KCONFIG_ALLCONFIG as a flag or a filename
  64that contains config symbols that the user requires to be set to a
  65specific value.  If KCONFIG_ALLCONFIG is used without a filename where
  66KCONFIG_ALLCONFIG == "" or KCONFIG_ALLCONFIG == "1", "make *config"
  67checks for a file named "all{yes/mod/no/def/random}.config"
  68(corresponding to the *config command that was used) for symbol values
  69that are to be forced.  If this file is not found, it checks for a
  70file named "all.config" to contain forced values.
  71
  72This enables you to create "miniature" config (miniconfig) or custom
  73config files containing just the config symbols that you are interested
  74in.  Then the kernel config system generates the full .config file,
  75including symbols of your miniconfig file.
  76
  77This 'KCONFIG_ALLCONFIG' file is a config file which contains
  78(usually a subset of all) preset config symbols.  These variable
  79settings are still subject to normal dependency checks.
  80
  81Examples:
  82        KCONFIG_ALLCONFIG=custom-notebook.config make allnoconfig
  83or
  84        KCONFIG_ALLCONFIG=mini.config make allnoconfig
  85or
  86        make KCONFIG_ALLCONFIG=mini.config allnoconfig
  87
  88These examples will disable most options (allnoconfig) but enable or
  89disable the options that are explicitly listed in the specified
  90mini-config files.
  91
  92______________________________________________________________________
  93Environment variables for 'randconfig'
  94
  95KCONFIG_SEED
  96--------------------------------------------------
  97You can set this to the integer value used to seed the RNG, if you want
  98to somehow debug the behaviour of the kconfig parser/frontends.
  99If not set, the current time will be used.
 100
 101KCONFIG_PROBABILITY
 102--------------------------------------------------
 103This variable can be used to skew the probabilities. This variable can
 104be unset or empty, or set to three different formats:
 105        KCONFIG_PROBABILITY     y:n split           y:m:n split
 106        -----------------------------------------------------------------
 107        unset or empty          50  : 50            33  : 33  : 34
 108        N                        N  : 100-N         N/2 : N/2 : 100-N
 109    [1] N:M                     N+M : 100-(N+M)      N  :  M  : 100-(N+M)
 110    [2] N:M:L                    N  : 100-N          M  :  L  : 100-(M+L)
 111
 112where N, M and L are integers (in base 10) in the range [0,100], and so
 113that:
 114    [1] N+M is in the range [0,100]
 115    [2] M+L is in the range [0,100]
 116
 117Examples:
 118        KCONFIG_PROBABILITY=10
 119                10% of booleans will be set to 'y', 90% to 'n'
 120                5% of tristates will be set to 'y', 5% to 'm', 90% to 'n'
 121        KCONFIG_PROBABILITY=15:25
 122                40% of booleans will be set to 'y', 60% to 'n'
 123                15% of tristates will be set to 'y', 25% to 'm', 60% to 'n'
 124        KCONFIG_PROBABILITY=10:15:15
 125                10% of booleans will be set to 'y', 90% to 'n'
 126                15% of tristates will be set to 'y', 15% to 'm', 70% to 'n'
 127
 128______________________________________________________________________
 129Environment variables for 'silentoldconfig'
 130
 131KCONFIG_NOSILENTUPDATE
 132--------------------------------------------------
 133If this variable has a non-blank value, it prevents silent kernel
 134config updates (requires explicit updates).
 135
 136KCONFIG_AUTOCONFIG
 137--------------------------------------------------
 138This environment variable can be set to specify the path & name of the
 139"auto.conf" file.  Its default value is "include/config/auto.conf".
 140
 141KCONFIG_TRISTATE
 142--------------------------------------------------
 143This environment variable can be set to specify the path & name of the
 144"tristate.conf" file.  Its default value is "include/config/tristate.conf".
 145
 146KCONFIG_AUTOHEADER
 147--------------------------------------------------
 148This environment variable can be set to specify the path & name of the
 149"autoconf.h" (header) file.
 150Its default value is "include/generated/autoconf.h".
 151
 152
 153======================================================================
 154menuconfig
 155--------------------------------------------------
 156
 157SEARCHING for CONFIG symbols
 158
 159Searching in menuconfig:
 160
 161        The Search function searches for kernel configuration symbol
 162        names, so you have to know something close to what you are
 163        looking for.
 164
 165        Example:
 166                /hotplug
 167                This lists all config symbols that contain "hotplug",
 168                e.g., HOTPLUG, HOTPLUG_CPU, MEMORY_HOTPLUG.
 169
 170        For search help, enter / followed TAB-TAB-TAB (to highlight
 171        <Help>) and Enter.  This will tell you that you can also use
 172        regular expressions (regexes) in the search string, so if you
 173        are not interested in MEMORY_HOTPLUG, you could try
 174
 175                /^hotplug
 176
 177______________________________________________________________________
 178User interface options for 'menuconfig'
 179
 180MENUCONFIG_COLOR
 181--------------------------------------------------
 182It is possible to select different color themes using the variable
 183MENUCONFIG_COLOR.  To select a theme use:
 184
 185        make MENUCONFIG_COLOR=<theme> menuconfig
 186
 187Available themes are:
 188  mono       => selects colors suitable for monochrome displays
 189  blackbg    => selects a color scheme with black background
 190  classic    => theme with blue background. The classic look
 191  bluetitle  => a LCD friendly version of classic. (default)
 192
 193MENUCONFIG_MODE
 194--------------------------------------------------
 195This mode shows all sub-menus in one large tree.
 196
 197Example:
 198        make MENUCONFIG_MODE=single_menu menuconfig
 199
 200
 201======================================================================
 202xconfig
 203--------------------------------------------------
 204
 205Searching in xconfig:
 206
 207        The Search function searches for kernel configuration symbol
 208        names, so you have to know something close to what you are
 209        looking for.
 210
 211        Example:
 212                Ctrl-F hotplug
 213        or
 214                Menu: File, Search, hotplug
 215
 216        lists all config symbol entries that contain "hotplug" in
 217        the symbol name.  In this Search dialog, you may change the
 218        config setting for any of the entries that are not grayed out.
 219        You can also enter a different search string without having
 220        to return to the main menu.
 221
 222
 223======================================================================
 224gconfig
 225--------------------------------------------------
 226
 227Searching in gconfig:
 228
 229        None (gconfig isn't maintained as well as xconfig or menuconfig);
 230        however, gconfig does have a few more viewing choices than
 231        xconfig does.
 232
 233###
 234
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