Root/Documentation/kbuild/kconfig.txt

1This file contains some assistance for using "make *config".
2
3Use "make help" to list all of the possible configuration targets.
4
5The xconfig ('qconf') and menuconfig ('mconf') programs also
6have embedded help text. Be sure to check it for navigation,
7search, and other general help text.
8
9======================================================================
10General
11--------------------------------------------------
12
13New kernel releases often introduce new config symbols. Often more
14important, new kernel releases may rename config symbols. When
15this happens, using a previously working .config file and running
16"make oldconfig" won't necessarily produce a working new kernel
17for you, so you may find that you need to see what NEW kernel
18symbols have been introduced.
19
20To 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
25and the config program will list as (NEW) any new symbols that have
26unknown values. Of course, the .config file is also updated with
27new (default) values, so you can use:
28
29    grep "(NEW)" conf.new
30
31to see the new config symbols or you can 'diff' the previous and
32new .config files to see the differences:
33
34    diff .config.old .config | less
35
36(Yes, we need something better here.)
37
38______________________________________________________________________
39Environment variables for '*config'
40
41KCONFIG_CONFIG
42--------------------------------------------------
43This environment variable can be used to specify a default kernel config
44file name to override the default name of ".config".
45
46KCONFIG_OVERWRITECONFIG
47--------------------------------------------------
48If you set KCONFIG_OVERWRITECONFIG in the environment, Kconfig will not
49break symlinks when .config is a symlink to somewhere else.
50
51KCONFIG_NOTIMESTAMP
52--------------------------------------------------
53If this environment variable exists and is non-null, the timestamp line
54in generated .config files is omitted.
55
56______________________________________________________________________
57Environment variables for '{allyes/allmod/allno/rand}config'
58
59KCONFIG_ALLCONFIG
60--------------------------------------------------
61(partially based on lkml email from/by Rob Landley, re: miniconfig)
62--------------------------------------------------
63The allyesconfig/allmodconfig/allnoconfig/randconfig variants can
64also use the environment variable KCONFIG_ALLCONFIG as a flag or a
65filename that contains config symbols that the user requires to be
66set to a specific value. If KCONFIG_ALLCONFIG is used without a
67filename, "make *config" checks for a file named
68"all{yes/mod/no/random}.config" (corresponding to the *config command
69that was used) for symbol values that are to be forced. If this file
70is not found, it checks for a file named "all.config" to contain forced
71values.
72
73This enables you to create "miniature" config (miniconfig) or custom
74config files containing just the config symbols that you are interested
75in. Then the kernel config system generates the full .config file,
76including symbols of your miniconfig file.
77
78This 'KCONFIG_ALLCONFIG' file is a config file which contains
79(usually a subset of all) preset config symbols. These variable
80settings are still subject to normal dependency checks.
81
82Examples:
83    KCONFIG_ALLCONFIG=custom-notebook.config make allnoconfig
84or
85    KCONFIG_ALLCONFIG=mini.config make allnoconfig
86or
87    make KCONFIG_ALLCONFIG=mini.config allnoconfig
88
89These examples will disable most options (allnoconfig) but enable or
90disable the options that are explicitly listed in the specified
91mini-config files.
92
93______________________________________________________________________
94Environment variables for 'silentoldconfig'
95
96KCONFIG_NOSILENTUPDATE
97--------------------------------------------------
98If this variable has a non-blank value, it prevents silent kernel
99config udpates (requires explicit updates).
100
101KCONFIG_AUTOCONFIG
102--------------------------------------------------
103This 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
106KCONFIG_TRISTATE
107--------------------------------------------------
108This environment variable can be set to specify the path & name of the
109"tristate.conf" file. Its default value is "include/config/tristate.conf".
110
111KCONFIG_AUTOHEADER
112--------------------------------------------------
113This environment variable can be set to specify the path & name of the
114"autoconf.h" (header) file.
115Its default value is "include/generated/autoconf.h".
116
117
118======================================================================
119menuconfig
120--------------------------------------------------
121
122SEARCHING for CONFIG symbols
123
124Searching in menuconfig:
125
126    The Search function searches for kernel configuration symbol
127    names, so you have to know something close to what you are
128    looking for.
129
130    Example:
131        /hotplug
132        This lists all config symbols that contain "hotplug",
133        e.g., HOTPLUG, HOTPLUG_CPU, MEMORY_HOTPLUG.
134
135    For search help, enter / followed TAB-TAB-TAB (to highlight
136    <Help>) and Enter. This will tell you that you can also use
137    regular expressions (regexes) in the search string, so if you
138    are not interested in MEMORY_HOTPLUG, you could try
139
140        /^hotplug
141
142______________________________________________________________________
143User interface options for 'menuconfig'
144
145MENUCONFIG_COLOR
146--------------------------------------------------
147It is possible to select different color themes using the variable
148MENUCONFIG_COLOR. To select a theme use:
149
150    make MENUCONFIG_COLOR=<theme> menuconfig
151
152Available themes are:
153  mono => selects colors suitable for monochrome displays
154  blackbg => selects a color scheme with black background
155  classic => theme with blue background. The classic look
156  bluetitle => a LCD friendly version of classic. (default)
157
158MENUCONFIG_MODE
159--------------------------------------------------
160This mode shows all sub-menus in one large tree.
161
162Example:
163    make MENUCONFIG_MODE=single_menu menuconfig
164
165
166======================================================================
167xconfig
168--------------------------------------------------
169
170Searching in xconfig:
171
172    The Search function searches for kernel configuration symbol
173    names, so you have to know something close to what you are
174    looking for.
175
176    Example:
177        Ctrl-F hotplug
178    or
179        Menu: File, Search, hotplug
180
181    lists all config symbol entries that contain "hotplug" in
182    the symbol name. In this Search dialog, you may change the
183    config setting for any of the entries that are not grayed out.
184    You can also enter a different search string without having
185    to return to the main menu.
186
187
188======================================================================
189gconfig
190--------------------------------------------------
191
192Searching in gconfig:
193
194    None (gconfig isn't maintained as well as xconfig or menuconfig);
195    however, gconfig does have a few more viewing choices than
196    xconfig does.
197
198###
199

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