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