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 'diff' the previous and
  32 new .config files to see the differences:
  33
  34         diff .config.old .config | less
  35
  36 (Yes, we need something better here.)
  37
  38 ______________________________________________________________________
  39 Environment variables for '*config'
  40
  41 KCONFIG_CONFIG
  42 --------------------------------------------------
  43 This environment variable can be used to specify a default kernel config
  44 file name to override the default name of ".config".
  45
  46 KCONFIG_OVERWRITECONFIG
  47 --------------------------------------------------
  48 If you set KCONFIG_OVERWRITECONFIG in the environment, Kconfig will not
  49 break symlinks when .config is a symlink to somewhere else.
  50
  51 ______________________________________________________________________
  52 Environment variables for '{allyes/allmod/allno/rand}config'
  53
  54 KCONFIG_ALLCONFIG
  55 --------------------------------------------------
  56 (partially based on lkml email from/by Rob Landley, re: miniconfig)
  57 --------------------------------------------------
  58 The allyesconfig/allmodconfig/allnoconfig/randconfig variants can
  59 also use the environment variable KCONFIG_ALLCONFIG as a flag or a
  60 filename that contains config symbols that the user requires to be
  61 set to a specific value.  If KCONFIG_ALLCONFIG is used without a
  62 filename, "make *config" checks for a file named
  63 "all{yes/mod/no/def/random}.config" (corresponding to the *config command
  64 that was used) for symbol values that are to be forced.  If this file
  65 is not found, it checks for a file named "all.config" to contain forced
  66 values.
  67
  68 This enables you to create "miniature" config (miniconfig) or custom
  69 config files containing just the config symbols that you are interested
  70 in.  Then the kernel config system generates the full .config file,
  71 including symbols of your miniconfig file.
  72
  73 This 'KCONFIG_ALLCONFIG' file is a config file which contains
  74 (usually a subset of all) preset config symbols.  These variable
  75 settings are still subject to normal dependency checks.
  76
  77 Examples:
  78         KCONFIG_ALLCONFIG=custom-notebook.config make allnoconfig
  79 or
  80         KCONFIG_ALLCONFIG=mini.config make allnoconfig
  81 or
  82         make KCONFIG_ALLCONFIG=mini.config allnoconfig
  83
  84 These examples will disable most options (allnoconfig) but enable or
  85 disable the options that are explicitly listed in the specified
  86 mini-config files.
  87
  88 ______________________________________________________________________
  89 Environment variables for 'silentoldconfig'
  90
  91 KCONFIG_NOSILENTUPDATE
  92 --------------------------------------------------
  93 If this variable has a non-blank value, it prevents silent kernel
  94 config updates (requires explicit updates).
  95
  96 KCONFIG_AUTOCONFIG
  97 --------------------------------------------------
  98 This environment variable can be set to specify the path & name of the
  99 "auto.conf" file.  Its default value is "include/config/auto.conf".
 100
 101 KCONFIG_TRISTATE
 102 --------------------------------------------------
 103 This environment variable can be set to specify the path & name of the
 104 "tristate.conf" file.  Its default value is "include/config/tristate.conf".
 105
 106 KCONFIG_AUTOHEADER
 107 --------------------------------------------------
 108 This environment variable can be set to specify the path & name of the
 109 "autoconf.h" (header) file.
 110 Its default value is "include/generated/autoconf.h".
 111
 112
 113 ======================================================================
 114 menuconfig
 115 --------------------------------------------------
 116
 117 SEARCHING for CONFIG symbols
 118
 119 Searching in menuconfig:
 120
 121         The Search function searches for kernel configuration symbol
 122         names, so you have to know something close to what you are
 123         looking for.
 124
 125         Example:
 126                 /hotplug
 127                 This lists all config symbols that contain "hotplug",
 128                 e.g., HOTPLUG, HOTPLUG_CPU, MEMORY_HOTPLUG.
 129
 130         For search help, enter / followed TAB-TAB-TAB (to highlight
 131         <Help>) and Enter.  This will tell you that you can also use
 132         regular expressions (regexes) in the search string, so if you
 133         are not interested in MEMORY_HOTPLUG, you could try
 134
 135                 /^hotplug
 136
 137 ______________________________________________________________________
 138 User interface options for 'menuconfig'
 139
 140 MENUCONFIG_COLOR
 141 --------------------------------------------------
 142 It is possible to select different color themes using the variable
 143 MENUCONFIG_COLOR.  To select a theme use:
 144
 145         make MENUCONFIG_COLOR=<theme> menuconfig
 146
 147 Available themes are:
 148   mono       => selects colors suitable for monochrome displays
 149   blackbg    => selects a color scheme with black background
 150   classic    => theme with blue background. The classic look
 151   bluetitle  => a LCD friendly version of classic. (default)
 152
 153 MENUCONFIG_MODE
 154 --------------------------------------------------
 155 This mode shows all sub-menus in one large tree.
 156
 157 Example:
 158         make MENUCONFIG_MODE=single_menu menuconfig
 159
 160
 161 ======================================================================
 162 xconfig
 163 --------------------------------------------------
 164
 165 Searching in xconfig:
 166
 167         The Search function searches for kernel configuration symbol
 168         names, so you have to know something close to what you are
 169         looking for.
 170
 171         Example:
 172                 Ctrl-F hotplug
 173         or
 174                 Menu: File, Search, hotplug
 175
 176         lists all config symbol entries that contain "hotplug" in
 177         the symbol name.  In this Search dialog, you may change the
 178         config setting for any of the entries that are not grayed out.
 179         You can also enter a different search string without having
 180         to return to the main menu.
 181
 182
 183 ======================================================================
 184 gconfig
 185 --------------------------------------------------
 186
 187 Searching in gconfig:
 188
 189         None (gconfig isn't maintained as well as xconfig or menuconfig);
 190         however, gconfig does have a few more viewing choices than
 191         xconfig does.
 192
 193 ###