Documentation/kbuild/kconfig.txt - linux - Git at Google

 This file contains some assistance for using "make *config".

 Use "make help" to list all of the possible configuration targets.

 The xconfig ('qconf') and menuconfig ('mconf') programs also
 have embedded help text.  Be sure to check it for navigation,
 search, and other general help text.

 ======================================================================
 General
 --------------------------------------------------

 New kernel releases often introduce new config symbols.  Often more
 important, new kernel releases may rename config symbols.  When
 this happens, using a previously working .config file and running
 "make oldconfig" won't necessarily produce a working new kernel
 for you, so you may find that you need to see what NEW kernel
 symbols have been introduced.

 To see a list of new config symbols when using "make oldconfig", use

 	cp user/some/old.config .config
 	yes "" | make oldconfig >conf.new

 and the config program will list as (NEW) any new symbols that have
 unknown values.  Of course, the .config file is also updated with
 new (default) values, so you can use:

 	grep "(NEW)" conf.new

 to see the new config symbols or you can use diffconfig to see the
 differences between the previous and new .config files:

 	scripts/diffconfig .config.old .config | less

 ______________________________________________________________________
 Environment variables for '*config'

 KCONFIG_CONFIG
 --------------------------------------------------
 This environment variable can be used to specify a default kernel config
 file name to override the default name of ".config".

 KCONFIG_OVERWRITECONFIG
 --------------------------------------------------
 If you set KCONFIG_OVERWRITECONFIG in the environment, Kconfig will not
 break symlinks when .config is a symlink to somewhere else.

 CONFIG_
 --------------------------------------------------
 If you set CONFIG_ in the environment, Kconfig will prefix all symbols
 with its value when saving the configuration, instead of using the default,
 "CONFIG_".

 ______________________________________________________________________
 Environment variables for '{allyes/allmod/allno/rand}config'

 KCONFIG_ALLCONFIG
 --------------------------------------------------
 (partially based on lkml email from/by Rob Landley, re: miniconfig)
 --------------------------------------------------
 The allyesconfig/allmodconfig/allnoconfig/randconfig variants can also
 use the environment variable KCONFIG_ALLCONFIG as a flag or a filename
 that contains config symbols that the user requires to be set to a
 specific value.  If KCONFIG_ALLCONFIG is used without a filename where
 KCONFIG_ALLCONFIG == "" or KCONFIG_ALLCONFIG == "1", "make *config"
 checks for a file named "all{yes/mod/no/def/random}.config"
 (corresponding to the *config command that was used) for symbol values
 that are to be forced.  If this file is not found, it checks for a
 file named "all.config" to contain forced values.

 This enables you to create "miniature" config (miniconfig) or custom
 config files containing just the config symbols that you are interested
 in.  Then the kernel config system generates the full .config file,
 including symbols of your miniconfig file.

 This 'KCONFIG_ALLCONFIG' file is a config file which contains
 (usually a subset of all) preset config symbols.  These variable
 settings are still subject to normal dependency checks.

 Examples:
 	KCONFIG_ALLCONFIG=custom-notebook.config make allnoconfig
 or
 	KCONFIG_ALLCONFIG=mini.config make allnoconfig
 or
 	make KCONFIG_ALLCONFIG=mini.config allnoconfig

 These examples will disable most options (allnoconfig) but enable or
 disable the options that are explicitly listed in the specified
 mini-config files.

 ______________________________________________________________________
 Environment variables for 'randconfig'

 KCONFIG_SEED
 --------------------------------------------------
 You can set this to the integer value used to seed the RNG, if you want
 to somehow debug the behaviour of the kconfig parser/frontends.
 If not set, the current time will be used.

 KCONFIG_PROBABILITY
 --------------------------------------------------
 This variable can be used to skew the probabilities. This variable can
 be unset or empty, or set to three different formats:
 	KCONFIG_PROBABILITY     y:n split           y:m:n split
 	-----------------------------------------------------------------
 	unset or empty          50  : 50            33  : 33  : 34
 	N                        N  : 100-N         N/2 : N/2 : 100-N
     [1] N:M                     N+M : 100-(N+M)      N  :  M  : 100-(N+M)
     [2] N:M:L                    N  : 100-N          M  :  L  : 100-(M+L)

 where N, M and L are integers (in base 10) in the range [0,100], and so
 that:
     [1] N+M is in the range [0,100]
     [2] M+L is in the range [0,100]

 Examples:
 	KCONFIG_PROBABILITY=10
 		10% of booleans will be set to 'y', 90% to 'n'
 		5% of tristates will be set to 'y', 5% to 'm', 90% to 'n'
 	KCONFIG_PROBABILITY=15:25
 		40% of booleans will be set to 'y', 60% to 'n'
 		15% of tristates will be set to 'y', 25% to 'm', 60% to 'n'
 	KCONFIG_PROBABILITY=10:15:15
 		10% of booleans will be set to 'y', 90% to 'n'
 		15% of tristates will be set to 'y', 15% to 'm', 70% to 'n'

 ______________________________________________________________________
 Environment variables for 'silentoldconfig'

 KCONFIG_NOSILENTUPDATE
 --------------------------------------------------
 If this variable has a non-blank value, it prevents silent kernel
 config updates (requires explicit updates).

 KCONFIG_AUTOCONFIG
 --------------------------------------------------
 This environment variable can be set to specify the path & name of the
 "auto.conf" file.  Its default value is "include/config/auto.conf".

 KCONFIG_TRISTATE
 --------------------------------------------------
 This environment variable can be set to specify the path & name of the
 "tristate.conf" file.  Its default value is "include/config/tristate.conf".

 KCONFIG_AUTOHEADER
 --------------------------------------------------
 This environment variable can be set to specify the path & name of the
 "autoconf.h" (header) file.
 Its default value is "include/generated/autoconf.h".


 ======================================================================
 menuconfig
 --------------------------------------------------

 SEARCHING for CONFIG symbols

 Searching in menuconfig:

 	The Search function searches for kernel configuration symbol
 	names, so you have to know something close to what you are
 	looking for.

 	Example:
 		/hotplug
 		This lists all config symbols that contain "hotplug",
 		e.g., HOTPLUG_CPU, MEMORY_HOTPLUG.

 	For search help, enter / followed TAB-TAB-TAB (to highlight
 	<Help>) and Enter.  This will tell you that you can also use
 	regular expressions (regexes) in the search string, so if you
 	are not interested in MEMORY_HOTPLUG, you could try

 		/^hotplug

 ______________________________________________________________________
 User interface options for 'menuconfig'

 MENUCONFIG_COLOR
 --------------------------------------------------
 It is possible to select different color themes using the variable
 MENUCONFIG_COLOR.  To select a theme use:

 	make MENUCONFIG_COLOR=<theme> menuconfig

 Available themes are:
   mono       => selects colors suitable for monochrome displays
   blackbg    => selects a color scheme with black background
   classic    => theme with blue background. The classic look
   bluetitle  => a LCD friendly version of classic. (default)

 MENUCONFIG_MODE
 --------------------------------------------------
 This mode shows all sub-menus in one large tree.

 Example:
 	make MENUCONFIG_MODE=single_menu menuconfig


 ======================================================================
 xconfig
 --------------------------------------------------

 Searching in xconfig:

 	The Search function searches for kernel configuration symbol
 	names, so you have to know something close to what you are
 	looking for.

 	Example:
 		Ctrl-F hotplug
 	or
 		Menu: File, Search, hotplug

 	lists all config symbol entries that contain "hotplug" in
 	the symbol name.  In this Search dialog, you may change the
 	config setting for any of the entries that are not grayed out.
 	You can also enter a different search string without having
 	to return to the main menu.


 ======================================================================
 gconfig
 --------------------------------------------------

 Searching in gconfig:

 	None (gconfig isn't maintained as well as xconfig or menuconfig);
 	however, gconfig does have a few more viewing choices than
 	xconfig does.

 ###
	This file contains some assistance for using "make *config".

	Use "make help" to list all of the possible configuration targets.

	The xconfig ('qconf') and menuconfig ('mconf') programs also
	have embedded help text. Be sure to check it for navigation,
	search, and other general help text.

	======================================================================
	General
	--------------------------------------------------

	New kernel releases often introduce new config symbols. Often more
	important, new kernel releases may rename config symbols. When
	this happens, using a previously working .config file and running
	"make oldconfig" won't necessarily produce a working new kernel
	for you, so you may find that you need to see what NEW kernel
	symbols have been introduced.

	To see a list of new config symbols when using "make oldconfig", use

	cp user/some/old.config .config
	yes "" \| make oldconfig >conf.new

	and the config program will list as (NEW) any new symbols that have
	unknown values. Of course, the .config file is also updated with
	new (default) values, so you can use:

	grep "(NEW)" conf.new

	to see the new config symbols or you can use diffconfig to see the
	differences between the previous and new .config files:

	scripts/diffconfig .config.old .config \| less

	______________________________________________________________________
	Environment variables for '*config'

	KCONFIG_CONFIG
	--------------------------------------------------
	This environment variable can be used to specify a default kernel config
	file name to override the default name of ".config".

	KCONFIG_OVERWRITECONFIG
	--------------------------------------------------
	If you set KCONFIG_OVERWRITECONFIG in the environment, Kconfig will not
	break symlinks when .config is a symlink to somewhere else.

	CONFIG_
	--------------------------------------------------
	If you set CONFIG_ in the environment, Kconfig will prefix all symbols
	with its value when saving the configuration, instead of using the default,
	"CONFIG_".

	______________________________________________________________________
	Environment variables for '{allyes/allmod/allno/rand}config'

	KCONFIG_ALLCONFIG
	--------------------------------------------------
	(partially based on lkml email from/by Rob Landley, re: miniconfig)
	--------------------------------------------------
	The allyesconfig/allmodconfig/allnoconfig/randconfig variants can also
	use the environment variable KCONFIG_ALLCONFIG as a flag or a filename
	that contains config symbols that the user requires to be set to a
	specific value. If KCONFIG_ALLCONFIG is used without a filename where
	KCONFIG_ALLCONFIG == "" or KCONFIG_ALLCONFIG == "1", "make *config"
	checks for a file named "all{yes/mod/no/def/random}.config"
	(corresponding to the *config command that was used) for symbol values
	that are to be forced. If this file is not found, it checks for a
	file named "all.config" to contain forced values.

	This enables you to create "miniature" config (miniconfig) or custom
	config files containing just the config symbols that you are interested
	in. Then the kernel config system generates the full .config file,
	including symbols of your miniconfig file.

	This 'KCONFIG_ALLCONFIG' file is a config file which contains
	(usually a subset of all) preset config symbols. These variable
	settings are still subject to normal dependency checks.

	Examples:
	KCONFIG_ALLCONFIG=custom-notebook.config make allnoconfig
	or
	KCONFIG_ALLCONFIG=mini.config make allnoconfig
	or
	make KCONFIG_ALLCONFIG=mini.config allnoconfig

	These examples will disable most options (allnoconfig) but enable or
	disable the options that are explicitly listed in the specified
	mini-config files.

	______________________________________________________________________
	Environment variables for 'randconfig'

	KCONFIG_SEED
	--------------------------------------------------
	You can set this to the integer value used to seed the RNG, if you want
	to somehow debug the behaviour of the kconfig parser/frontends.
	If not set, the current time will be used.

	KCONFIG_PROBABILITY
	--------------------------------------------------
	This variable can be used to skew the probabilities. This variable can
	be unset or empty, or set to three different formats:
	KCONFIG_PROBABILITY y:n split y:m:n split
	-----------------------------------------------------------------
	unset or empty 50 : 50 33 : 33 : 34
	N N : 100-N N/2 : N/2 : 100-N
	[1] N:M N+M : 100-(N+M) N : M : 100-(N+M)
	[2] N:M:L N : 100-N M : L : 100-(M+L)

	where N, M and L are integers (in base 10) in the range [0,100], and so
	that:
	[1] N+M is in the range [0,100]
	[2] M+L is in the range [0,100]

	Examples:
	KCONFIG_PROBABILITY=10
	10% of booleans will be set to 'y', 90% to 'n'
	5% of tristates will be set to 'y', 5% to 'm', 90% to 'n'
	KCONFIG_PROBABILITY=15:25
	40% of booleans will be set to 'y', 60% to 'n'
	15% of tristates will be set to 'y', 25% to 'm', 60% to 'n'
	KCONFIG_PROBABILITY=10:15:15
	10% of booleans will be set to 'y', 90% to 'n'
	15% of tristates will be set to 'y', 15% to 'm', 70% to 'n'

	______________________________________________________________________
	Environment variables for 'silentoldconfig'

	KCONFIG_NOSILENTUPDATE
	--------------------------------------------------
	If this variable has a non-blank value, it prevents silent kernel
	config updates (requires explicit updates).

	KCONFIG_AUTOCONFIG
	--------------------------------------------------
	This environment variable can be set to specify the path & name of the
	"auto.conf" file. Its default value is "include/config/auto.conf".

	KCONFIG_TRISTATE
	--------------------------------------------------
	This environment variable can be set to specify the path & name of the
	"tristate.conf" file. Its default value is "include/config/tristate.conf".

	KCONFIG_AUTOHEADER
	--------------------------------------------------
	This environment variable can be set to specify the path & name of the
	"autoconf.h" (header) file.
	Its default value is "include/generated/autoconf.h".


	======================================================================
	menuconfig
	--------------------------------------------------

	SEARCHING for CONFIG symbols

	Searching in menuconfig:

	The Search function searches for kernel configuration symbol
	names, so you have to know something close to what you are
	looking for.

	Example:
	/hotplug
	This lists all config symbols that contain "hotplug",
	e.g., HOTPLUG_CPU, MEMORY_HOTPLUG.

	For search help, enter / followed TAB-TAB-TAB (to highlight
	<Help>) and Enter. This will tell you that you can also use
	regular expressions (regexes) in the search string, so if you
	are not interested in MEMORY_HOTPLUG, you could try

	/^hotplug

	______________________________________________________________________
	User interface options for 'menuconfig'

	MENUCONFIG_COLOR
	--------------------------------------------------
	It is possible to select different color themes using the variable
	MENUCONFIG_COLOR. To select a theme use:

	make MENUCONFIG_COLOR=<theme> menuconfig

	Available themes are:
	mono => selects colors suitable for monochrome displays
	blackbg => selects a color scheme with black background
	classic => theme with blue background. The classic look
	bluetitle => a LCD friendly version of classic. (default)

	MENUCONFIG_MODE
	--------------------------------------------------
	This mode shows all sub-menus in one large tree.

	Example:
	make MENUCONFIG_MODE=single_menu menuconfig


	======================================================================
	xconfig
	--------------------------------------------------

	Searching in xconfig:

	The Search function searches for kernel configuration symbol
	names, so you have to know something close to what you are
	looking for.

	Example:
	Ctrl-F hotplug
	or
	Menu: File, Search, hotplug

	lists all config symbol entries that contain "hotplug" in
	the symbol name. In this Search dialog, you may change the
	config setting for any of the entries that are not grayed out.
	You can also enter a different search string without having
	to return to the main menu.


	======================================================================
	gconfig
	--------------------------------------------------

	Searching in gconfig:

	None (gconfig isn't maintained as well as xconfig or menuconfig);
	however, gconfig does have a few more viewing choices than
	xconfig does.

	###