Documentation/kbuild/kconfig.txt

   1 This file contains some assistance for using "make *config".
   2
   3 Use "make help" to list all of the possible configuration targets.
   4
   5 The xconfig ('qconf') and menuconfig ('mconf') programs also
   6 have embedded help text.  Be sure to check it for navigation,
   7 search, and other general help text.
   8
   9 ======================================================================
  10 General
  11 --------------------------------------------------
  12
  13 New kernel releases often introduce new config symbols.  Often more
  14 important, new kernel releases may rename config symbols.  When
  15 this happens, using a previously working .config file and running
  16 "make oldconfig" won't necessarily produce a working new kernel
  17 for you, so you may find that you need to see what NEW kernel
  18 symbols have been introduced.
  19
  20 To 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
  25 and the config program will list as (NEW) any new symbols that have
  26 unknown values.  Of course, the .config file is also updated with
  27 new (default) values, so you can use:
  28
  29         grep "(NEW)" conf.new
  30
  31 to see the new config symbols or you can use diffconfig to see the
  32 differences between the previous and new .config files:
  33
  34         scripts/diffconfig .config.old .config | less
  35
  36 ______________________________________________________________________
  37 Environment variables for '*config'
  38
  39 KCONFIG_CONFIG
  40 --------------------------------------------------
  41 This environment variable can be used to specify a default kernel config
  42 file name to override the default name of ".config".
  43
  44 KCONFIG_OVERWRITECONFIG
  45 --------------------------------------------------
  46 If you set KCONFIG_OVERWRITECONFIG in the environment, Kconfig will not
  47 break symlinks when .config is a symlink to somewhere else.
  48
  49 CONFIG_
  50 --------------------------------------------------
  51 If you set CONFIG_ in the environment, Kconfig will prefix all symbols
  52 with its value when saving the configuration, instead of using the default,
  53 "CONFIG_".
  54
  55 ______________________________________________________________________
  56 Environment variables for '{allyes/allmod/allno/rand}config'
  57
  58 KCONFIG_ALLCONFIG
  59 --------------------------------------------------
  60 (partially based on lkml email from/by Rob Landley, re: miniconfig)
  61 --------------------------------------------------
  62 The allyesconfig/allmodconfig/allnoconfig/randconfig variants can also
  63 use the environment variable KCONFIG_ALLCONFIG as a flag or a filename
  64 that contains config symbols that the user requires to be set to a
  65 specific value.  If KCONFIG_ALLCONFIG is used without a filename where
  66 KCONFIG_ALLCONFIG == "" or KCONFIG_ALLCONFIG == "1", "make *config"
  67 checks for a file named "all{yes/mod/no/def/random}.config"
  68 (corresponding to the *config command that was used) for symbol values
  69 that are to be forced.  If this file is not found, it checks for a
  70 file named "all.config" to contain forced values.
  71
  72 This enables you to create "miniature" config (miniconfig) or custom
  73 config files containing just the config symbols that you are interested
  74 in.  Then the kernel config system generates the full .config file,
  75 including symbols of your miniconfig file.
  76
  77 This 'KCONFIG_ALLCONFIG' file is a config file which contains
  78 (usually a subset of all) preset config symbols.  These variable
  79 settings are still subject to normal dependency checks.
  80
  81 Examples:
  82         KCONFIG_ALLCONFIG=custom-notebook.config make allnoconfig
  83 or
  84         KCONFIG_ALLCONFIG=mini.config make allnoconfig
  85 or
  86         make KCONFIG_ALLCONFIG=mini.config allnoconfig
  87
  88 These examples will disable most options (allnoconfig) but enable or
  89 disable the options that are explicitly listed in the specified
  90 mini-config files.
  91
  92 ______________________________________________________________________
  93 Environment variables for 'randconfig'
  94
  95 KCONFIG_SEED
  96 --------------------------------------------------
  97 You can set this to the integer value used to seed the RNG, if you want
  98 to somehow debug the behaviour of the kconfig parser/frontends.
  99 If not set, the current time will be used.
 100
 101 KCONFIG_PROBABILITY
 102 --------------------------------------------------
 103 This variable can be used to skew the probabilities. This variable can
 104 be 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
 112 where N, M and L are integers (in base 10) in the range [0,100], and so
 113 that:
 114     [1] N+M is in the range [0,100]
 115     [2] M+L is in the range [0,100]
 116
 117 Examples:
 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 ______________________________________________________________________
 129 Environment variables for 'silentoldconfig'
 130
 131 KCONFIG_NOSILENTUPDATE
 132 --------------------------------------------------
 133 If this variable has a non-blank value, it prevents silent kernel
 134 config updates (requires explicit updates).
 135
 136 KCONFIG_AUTOCONFIG
 137 --------------------------------------------------
 138 This 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
 141 KCONFIG_TRISTATE
 142 --------------------------------------------------
 143 This 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
 146 KCONFIG_AUTOHEADER
 147 --------------------------------------------------
 148 This environment variable can be set to specify the path & name of the
 149 "autoconf.h" (header) file.
 150 Its default value is "include/generated/autoconf.h".
 151
 152
 153 ======================================================================
 154 menuconfig
 155 --------------------------------------------------
 156
 157 SEARCHING for CONFIG symbols
 158
 159 Searching 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_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         When searching, symbols are sorted thus:
 178           - first, exact matches, sorted alphabetically (an exact match
 179             is when the search matches the complete symbol name);
 180           - then, other matches, sorted alphabetically.
 181         For example: ^ATH.K matches:
 182             ATH5K ATH9K ATH5K_AHB ATH5K_DEBUG [...] ATH6KL ATH6KL_DEBUG
 183             [...] ATH9K_AHB ATH9K_BTCOEX_SUPPORT ATH9K_COMMON [...]
 184         of which only ATH5K and ATH9K match exactly and so are sorted
 185         first (and in alphabetical order), then come all other symbols,
 186         sorted in alphabetical order.
 187
 188 ______________________________________________________________________
 189 User interface options for 'menuconfig'
 190
 191 MENUCONFIG_COLOR
 192 --------------------------------------------------
 193 It is possible to select different color themes using the variable
 194 MENUCONFIG_COLOR.  To select a theme use:
 195
 196         make MENUCONFIG_COLOR=<theme> menuconfig
 197
 198 Available themes are:
 199   mono       => selects colors suitable for monochrome displays
 200   blackbg    => selects a color scheme with black background
 201   classic    => theme with blue background. The classic look
 202   bluetitle  => a LCD friendly version of classic. (default)
 203
 204 MENUCONFIG_MODE
 205 --------------------------------------------------
 206 This mode shows all sub-menus in one large tree.
 207
 208 Example:
 209         make MENUCONFIG_MODE=single_menu menuconfig
 210
 211
 212 ======================================================================
 213 xconfig
 214 --------------------------------------------------
 215
 216 Searching in xconfig:
 217
 218         The Search function searches for kernel configuration symbol
 219         names, so you have to know something close to what you are
 220         looking for.
 221
 222         Example:
 223                 Ctrl-F hotplug
 224         or
 225                 Menu: File, Search, hotplug
 226
 227         lists all config symbol entries that contain "hotplug" in
 228         the symbol name.  In this Search dialog, you may change the
 229         config setting for any of the entries that are not grayed out.
 230         You can also enter a different search string without having
 231         to return to the main menu.
 232
 233
 234 ======================================================================
 235 gconfig
 236 --------------------------------------------------
 237
 238 Searching in gconfig:
 239
 240         None (gconfig isn't maintained as well as xconfig or menuconfig);
 241         however, gconfig does have a few more viewing choices than
 242         xconfig does.
 243
 244 ###