Documentation/kbuild/kconfig.rst

   1 ===================
   2 Kconfig make config
   3 ===================
   4
   5 This file contains some assistance for using `make *config`.
   6
   7 Use "make help" to list all of the possible configuration targets.
   8
   9 The xconfig ('qconf'), menuconfig ('mconf'), and nconfig ('nconf')
  10 programs also have embedded help text.  Be sure to check that for
  11 navigation, search, and other general help text.
  12
  13 General
  14 -------
  15
  16 New kernel releases often introduce new config symbols.  Often more
  17 important, new kernel releases may rename config symbols.  When
  18 this happens, using a previously working .config file and running
  19 "make oldconfig" won't necessarily produce a working new kernel
  20 for you, so you may find that you need to see what NEW kernel
  21 symbols have been introduced.
  22
  23 To see a list of new config symbols, use::
  24
  25         cp user/some/old.config .config
  26         make listnewconfig
  27
  28 and the config program will list any new symbols, one per line.
  29
  30 Alternatively, you can use the brute force method::
  31
  32         make oldconfig
  33         scripts/diffconfig .config.old .config | less
  34
  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
  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 --------------------------------------------------
  64
  65 The allyesconfig/allmodconfig/allnoconfig/randconfig variants can also
  66 use the environment variable KCONFIG_ALLCONFIG as a flag or a filename
  67 that contains config symbols that the user requires to be set to a
  68 specific value.  If KCONFIG_ALLCONFIG is used without a filename where
  69 KCONFIG_ALLCONFIG == "" or KCONFIG_ALLCONFIG == "1", `make *config`
  70 checks for a file named "all{yes/mod/no/def/random}.config"
  71 (corresponding to the `*config` command that was used) for symbol values
  72 that are to be forced.  If this file is not found, it checks for a
  73 file named "all.config" to contain forced values.
  74
  75 This enables you to create "miniature" config (miniconfig) or custom
  76 config files containing just the config symbols that you are interested
  77 in.  Then the kernel config system generates the full .config file,
  78 including symbols of your miniconfig file.
  79
  80 This 'KCONFIG_ALLCONFIG' file is a config file which contains
  81 (usually a subset of all) preset config symbols.  These variable
  82 settings are still subject to normal dependency checks.
  83
  84 Examples::
  85
  86         KCONFIG_ALLCONFIG=custom-notebook.config make allnoconfig
  87
  88 or::
  89
  90         KCONFIG_ALLCONFIG=mini.config make allnoconfig
  91
  92 or::
  93
  94         make KCONFIG_ALLCONFIG=mini.config allnoconfig
  95
  96 These examples will disable most options (allnoconfig) but enable or
  97 disable the options that are explicitly listed in the specified
  98 mini-config files.
  99
 100 ----------------------------------------------------------------------
 101
 102 Environment variables for 'randconfig'
 103
 104 KCONFIG_SEED
 105 ------------
 106 You can set this to the integer value used to seed the RNG, if you want
 107 to somehow debug the behaviour of the kconfig parser/frontends.
 108 If not set, the current time will be used.
 109
 110 KCONFIG_PROBABILITY
 111 -------------------
 112 This variable can be used to skew the probabilities. This variable can
 113 be unset or empty, or set to three different formats:
 114
 115     =======================     ==================  =====================
 116         KCONFIG_PROBABILITY     y:n split           y:m:n split
 117     =======================     ==================  =====================
 118         unset or empty          50  : 50            33  : 33  : 34
 119         N                        N  : 100-N         N/2 : N/2 : 100-N
 120     [1] N:M                     N+M : 100-(N+M)      N  :  M  : 100-(N+M)
 121     [2] N:M:L                    N  : 100-N          M  :  L  : 100-(M+L)
 122     =======================     ==================  =====================
 123
 124 where N, M and L are integers (in base 10) in the range [0,100], and so
 125 that:
 126
 127     [1] N+M is in the range [0,100]
 128
 129     [2] M+L is in the range [0,100]
 130
 131 Examples::
 132
 133         KCONFIG_PROBABILITY=10
 134                 10% of booleans will be set to 'y', 90% to 'n'
 135                 5% of tristates will be set to 'y', 5% to 'm', 90% to 'n'
 136         KCONFIG_PROBABILITY=15:25
 137                 40% of booleans will be set to 'y', 60% to 'n'
 138                 15% of tristates will be set to 'y', 25% to 'm', 60% to 'n'
 139         KCONFIG_PROBABILITY=10:15:15
 140                 10% of booleans will be set to 'y', 90% to 'n'
 141                 15% of tristates will be set to 'y', 15% to 'm', 70% to 'n'
 142
 143 ----------------------------------------------------------------------
 144
 145 Environment variables for 'syncconfig'
 146
 147 KCONFIG_NOSILENTUPDATE
 148 ----------------------
 149 If this variable has a non-blank value, it prevents silent kernel
 150 config updates (requires explicit updates).
 151
 152 KCONFIG_AUTOCONFIG
 153 ------------------
 154 This environment variable can be set to specify the path & name of the
 155 "auto.conf" file.  Its default value is "include/config/auto.conf".
 156
 157 KCONFIG_AUTOHEADER
 158 ------------------
 159 This environment variable can be set to specify the path & name of the
 160 "autoconf.h" (header) file.
 161 Its default value is "include/generated/autoconf.h".
 162
 163
 164 ----------------------------------------------------------------------
 165
 166 menuconfig
 167 ----------
 168
 169 SEARCHING for CONFIG symbols
 170
 171 Searching in menuconfig:
 172
 173         The Search function searches for kernel configuration symbol
 174         names, so you have to know something close to what you are
 175         looking for.
 176
 177         Example::
 178
 179                 /hotplug
 180                 This lists all config symbols that contain "hotplug",
 181                 e.g., HOTPLUG_CPU, MEMORY_HOTPLUG.
 182
 183         For search help, enter / followed by TAB-TAB (to highlight
 184         <Help>) and Enter.  This will tell you that you can also use
 185         regular expressions (regexes) in the search string, so if you
 186         are not interested in MEMORY_HOTPLUG, you could try::
 187
 188                 /^hotplug
 189
 190         When searching, symbols are sorted thus:
 191
 192           - first, exact matches, sorted alphabetically (an exact match
 193             is when the search matches the complete symbol name);
 194           - then, other matches, sorted alphabetically.
 195
 196         For example: ^ATH.K matches:
 197
 198             ATH5K ATH9K ATH5K_AHB ATH5K_DEBUG [...] ATH6KL ATH6KL_DEBUG
 199             [...] ATH9K_AHB ATH9K_BTCOEX_SUPPORT ATH9K_COMMON [...]
 200
 201         of which only ATH5K and ATH9K match exactly and so are sorted
 202         first (and in alphabetical order), then come all other symbols,
 203         sorted in alphabetical order.
 204
 205 ----------------------------------------------------------------------
 206
 207 User interface options for 'menuconfig'
 208
 209 MENUCONFIG_COLOR
 210 ----------------
 211 It is possible to select different color themes using the variable
 212 MENUCONFIG_COLOR.  To select a theme use::
 213
 214         make MENUCONFIG_COLOR=<theme> menuconfig
 215
 216 Available themes are::
 217
 218   - mono       => selects colors suitable for monochrome displays
 219   - blackbg    => selects a color scheme with black background
 220   - classic    => theme with blue background. The classic look
 221   - bluetitle  => a LCD friendly version of classic. (default)
 222
 223 MENUCONFIG_MODE
 224 ---------------
 225 This mode shows all sub-menus in one large tree.
 226
 227 Example::
 228
 229         make MENUCONFIG_MODE=single_menu menuconfig
 230
 231 ----------------------------------------------------------------------
 232
 233 nconfig
 234 -------
 235
 236 nconfig is an alternate text-based configurator.  It lists function
 237 keys across the bottom of the terminal (window) that execute commands.
 238 You can also just use the corresponding numeric key to execute the
 239 commands unless you are in a data entry window.  E.g., instead of F6
 240 for Save, you can just press 6.
 241
 242 Use F1 for Global help or F3 for the Short help menu.
 243
 244 Searching in nconfig:
 245
 246         You can search either in the menu entry "prompt" strings
 247         or in the configuration symbols.
 248
 249         Use / to begin a search through the menu entries.  This does
 250         not support regular expressions.  Use <Down> or <Up> for
 251         Next hit and Previous hit, respectively.  Use <Esc> to
 252         terminate the search mode.
 253
 254         F8 (SymSearch) searches the configuration symbols for the
 255         given string or regular expression (regex).
 256
 257 NCONFIG_MODE
 258 ------------
 259 This mode shows all sub-menus in one large tree.
 260
 261 Example::
 262
 263         make NCONFIG_MODE=single_menu nconfig
 264
 265 ----------------------------------------------------------------------
 266
 267 xconfig
 268 -------
 269
 270 Searching in xconfig:
 271
 272         The Search function searches for kernel configuration symbol
 273         names, so you have to know something close to what you are
 274         looking for.
 275
 276         Example::
 277
 278                 Ctrl-F hotplug
 279
 280         or::
 281
 282                 Menu: File, Search, hotplug
 283
 284         lists all config symbol entries that contain "hotplug" in
 285         the symbol name.  In this Search dialog, you may change the
 286         config setting for any of the entries that are not grayed out.
 287         You can also enter a different search string without having
 288         to return to the main menu.
 289
 290
 291 ----------------------------------------------------------------------
 292
 293 gconfig
 294 -------
 295
 296 Searching in gconfig:
 297
 298         There is no search command in gconfig.  However, gconfig does
 299         have several different viewing choices, modes, and options.