kconfig.txt

- usage help for make *config

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 'diff' the previous and

new .config files to see the differences:

diff .config.old .config | less

(Yes, we need something better here.)

======================================================================

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, 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

______________________________________________________________________

Color Themes for 'menuconfig'

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)

______________________________________________________________________

Environment variables in 'menuconfig'

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, "make *config" checks for a file named

"all{yes/mod/no/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 dependencies of your miniconfig file, based on the 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.

KCONFIG_NOSILENTUPDATE

--------------------------------------------------

If this variable has a non-blank value, it prevents silent kernel

config udpates (requires explicit updates).

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.

KCONFIG_NOTIMESTAMP

--------------------------------------------------

If this environment variable exists and is non-null, the timestamp line

in generated .config files is omitted.

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_AUTOHEADER

--------------------------------------------------

This environment variable can be set to specify the path & name of the

"autoconf.h" (header) file. Its default value is "include/linux/autoconf.h".

______________________________________________________________________

menuconfig User Interface Options

----------------------------------------------------------------------

MENUCONFIG_MODE

--------------------------------------------------

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

Example:

MENUCONFIG_MODE=single_menu make 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.

###

number of formats: PostScript (.ps), PDF, HTML, & man-pages, among others.

After installation, "make psdocs", "make pdfdocs", "make htmldocs",

or "make mandocs" will render the documentation in the requested format.

INSTALLING the kernel source:

You can find more information on using the Linux kernel config tools

in Documentation/kbuild/make-configs.txt.

- Verbose kernel compile/build output:

Normally the kernel build system runs in a fairly quiet mode (but not

totally silent). However, sometimes you or other kernel developers need

to see compile, link, or other commands exactly as they are executed.

For this, use "verbose" build mode. This is done by inserting

"V=1" in the "make" command. E.g.:

make V=1 all

To have the build system also tell the reason for the rebuild of each

target, use "V=2". The default is "V=0".