diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/kconfig-language.txt | 395 | ||||
| -rw-r--r-- | Documentation/kconfig.txt | 237 |
2 files changed, 632 insertions, 0 deletions
diff --git a/Documentation/kconfig-language.txt b/Documentation/kconfig-language.txt new file mode 100644 index 0000000..350f733 --- /dev/null +++ b/Documentation/kconfig-language.txt @@ -0,0 +1,395 @@ +Introduction +------------ + +The configuration database is a collection of configuration options +organized in a tree structure: + + +- Code maturity level options + | +- Prompt for development and/or incomplete code/drivers + +- General setup + | +- Networking support + | +- System V IPC + | +- BSD Process Accounting + | +- Sysctl support + +- Loadable module support + | +- Enable loadable module support + | +- Set version information on all module symbols + | +- Kernel module loader + +- ... + +Every entry has its own dependencies. These dependencies are used +to determine the visibility of an entry. Any child entry is only +visible if its parent entry is also visible. + +Menu entries +------------ + +Most entries define a config option; all other entries help to organize +them. A single configuration option is defined like this: + +config MODVERSIONS + bool "Set version information on all module symbols" + depends on MODULES + help + Usually, modules have to be recompiled whenever you switch to a new + kernel. ... + +Every line starts with a key word and can be followed by multiple +arguments. "config" starts a new config entry. The following lines +define attributes for this config option. Attributes can be the type of +the config option, input prompt, dependencies, help text and default +values. A config option can be defined multiple times with the same +name, but every definition can have only a single input prompt and the +type must not conflict. + +Menu attributes +--------------- + +A menu entry can have a number of attributes. Not all of them are +applicable everywhere (see syntax). + +- type definition: "bool"/"tristate"/"string"/"hex"/"int" + Every config option must have a type. There are only two basic types: + tristate and string; the other types are based on these two. The type + definition optionally accepts an input prompt, so these two examples + are equivalent: + + bool "Networking support" + and + bool + prompt "Networking support" + +- input prompt: "prompt" <prompt> ["if" <expr>] + Every menu entry can have at most one prompt, which is used to display + to the user. Optionally dependencies only for this prompt can be added + with "if". + +- default value: "default" <expr> ["if" <expr>] + A config option can have any number of default values. If multiple + default values are visible, only the first defined one is active. + Default values are not limited to the menu entry where they are + defined. This means the default can be defined somewhere else or be + overridden by an earlier definition. + The default value is only assigned to the config symbol if no other + value was set by the user (via the input prompt above). If an input + prompt is visible the default value is presented to the user and can + be overridden by him. + Optionally, dependencies only for this default value can be added with + "if". + +- type definition + default value: + "def_bool"/"def_tristate" <expr> ["if" <expr>] + This is a shorthand notation for a type definition plus a value. + Optionally dependencies for this default value can be added with "if". + +- dependencies: "depends on" <expr> + This defines a dependency for this menu entry. If multiple + dependencies are defined, they are connected with '&&'. Dependencies + are applied to all other options within this menu entry (which also + accept an "if" expression), so these two examples are equivalent: + + bool "foo" if BAR + default y if BAR + and + depends on BAR + bool "foo" + default y + +- reverse dependencies: "select" <symbol> ["if" <expr>] + While normal dependencies reduce the upper limit of a symbol (see + below), reverse dependencies can be used to force a lower limit of + another symbol. The value of the current menu symbol is used as the + minimal value <symbol> can be set to. If <symbol> is selected multiple + times, the limit is set to the largest selection. + Reverse dependencies can only be used with boolean or tristate + symbols. + Note: + select should be used with care. select will force + a symbol to a value without visiting the dependencies. + By abusing select you are able to select a symbol FOO even + if FOO depends on BAR that is not set. + In general use select only for non-visible symbols + (no prompts anywhere) and for symbols with no dependencies. + That will limit the usefulness but on the other hand avoid + the illegal configurations all over. + +- limiting menu display: "visible if" <expr> + This attribute is only applicable to menu blocks, if the condition is + false, the menu block is not displayed to the user (the symbols + contained there can still be selected by other symbols, though). It is + similar to a conditional "prompt" attribute for individual menu + entries. Default value of "visible" is true. + +- numerical ranges: "range" <symbol> <symbol> ["if" <expr>] + This allows to limit the range of possible input values for int + and hex symbols. The user can only input a value which is larger than + or equal to the first symbol and smaller than or equal to the second + symbol. + +- help text: "help" or "---help---" + This defines a help text. The end of the help text is determined by + the indentation level, this means it ends at the first line which has + a smaller indentation than the first line of the help text. + "---help---" and "help" do not differ in behaviour, "---help---" is + used to help visually separate configuration logic from help within + the file as an aid to developers. + +- misc options: "option" <symbol>[=<value>] + Various less common options can be defined via this option syntax, + which can modify the behaviour of the menu entry and its config + symbol. These options are currently possible: + + - "defconfig_list" + This declares a list of default entries which can be used when + looking for the default configuration (which is used when the main + .config doesn't exists yet.) + + - "modules" + This declares the symbol to be used as the MODULES symbol, which + enables the third modular state for all config symbols. + At most one symbol may have the "modules" option set. + + - "env"=<value> + This imports the environment variable into Kconfig. It behaves like + a default, except that the value comes from the environment, this + also means that the behaviour when mixing it with normal defaults is + undefined at this point. The symbol is currently not exported back + to the build environment (if this is desired, it can be done via + another symbol). + + - "allnoconfig_y" + This declares the symbol as one that should have the value y when + using "allnoconfig". Used for symbols that hide other symbols. + +Menu dependencies +----------------- + +Dependencies define the visibility of a menu entry and can also reduce +the input range of tristate symbols. The tristate logic used in the +expressions uses one more state than normal boolean logic to express the +module state. Dependency expressions have the following syntax: + +<expr> ::= <symbol> (1) + <symbol> '=' <symbol> (2) + <symbol> '!=' <symbol> (3) + '(' <expr> ')' (4) + '!' <expr> (5) + <expr> '&&' <expr> (6) + <expr> '||' <expr> (7) + +Expressions are listed in decreasing order of precedence. + +(1) Convert the symbol into an expression. Boolean and tristate symbols + are simply converted into the respective expression values. All + other symbol types result in 'n'. +(2) If the values of both symbols are equal, it returns 'y', + otherwise 'n'. +(3) If the values of both symbols are equal, it returns 'n', + otherwise 'y'. +(4) Returns the value of the expression. Used to override precedence. +(5) Returns the result of (2-/expr/). +(6) Returns the result of min(/expr/, /expr/). +(7) Returns the result of max(/expr/, /expr/). + +An expression can have a value of 'n', 'm' or 'y' (or 0, 1, 2 +respectively for calculations). A menu entry becomes visible when its +expression evaluates to 'm' or 'y'. + +There are two types of symbols: constant and non-constant symbols. +Non-constant symbols are the most common ones and are defined with the +'config' statement. Non-constant symbols consist entirely of alphanumeric +characters or underscores. +Constant symbols are only part of expressions. Constant symbols are +always surrounded by single or double quotes. Within the quote, any +other character is allowed and the quotes can be escaped using '\'. + +Menu structure +-------------- + +The position of a menu entry in the tree is determined in two ways. First +it can be specified explicitly: + +menu "Network device support" + depends on NET + +config NETDEVICES + ... + +endmenu + +All entries within the "menu" ... "endmenu" block become a submenu of +"Network device support". All subentries inherit the dependencies from +the menu entry, e.g. this means the dependency "NET" is added to the +dependency list of the config option NETDEVICES. + +The other way to generate the menu structure is done by analyzing the +dependencies. If a menu entry somehow depends on the previous entry, it +can be made a submenu of it. First, the previous (parent) symbol must +be part of the dependency list and then one of these two conditions +must be true: +- the child entry must become invisible, if the parent is set to 'n' +- the child entry must only be visible, if the parent is visible + +config MODULES + bool "Enable loadable module support" + +config MODVERSIONS + bool "Set version information on all module symbols" + depends on MODULES + +comment "module support disabled" + depends on !MODULES + +MODVERSIONS directly depends on MODULES, this means it's only visible if +MODULES is different from 'n'. The comment on the other hand is always +visible when MODULES is visible (the (empty) dependency of MODULES is +also part of the comment dependencies). + + +Kconfig syntax +-------------- + +The configuration file describes a series of menu entries, where every +line starts with a keyword (except help texts). The following keywords +end a menu entry: +- config +- menuconfig +- choice/endchoice +- comment +- menu/endmenu +- if/endif +- source +The first five also start the definition of a menu entry. + +config: + + "config" <symbol> + <config options> + +This defines a config symbol <symbol> and accepts any of above +attributes as options. + +menuconfig: + "menuconfig" <symbol> + <config options> + +This is similar to the simple config entry above, but it also gives a +hint to front ends, that all suboptions should be displayed as a +separate list of options. + +choices: + + "choice" [symbol] + <choice options> + <choice block> + "endchoice" + +This defines a choice group and accepts any of the above attributes as +options. A choice can only be of type bool or tristate, while a boolean +choice only allows a single config entry to be selected, a tristate +choice also allows any number of config entries to be set to 'm'. This +can be used if multiple drivers for a single hardware exists and only a +single driver can be compiled/loaded into the kernel, but all drivers +can be compiled as modules. +A choice accepts another option "optional", which allows to set the +choice to 'n' and no entry needs to be selected. +If no [symbol] is associated with a choice, then you can not have multiple +definitions of that choice. If a [symbol] is associated to the choice, +then you may define the same choice (ie. with the same entries) in another +place. + +comment: + + "comment" <prompt> + <comment options> + +This defines a comment which is displayed to the user during the +configuration process and is also echoed to the output files. The only +possible options are dependencies. + +menu: + + "menu" <prompt> + <menu options> + <menu block> + "endmenu" + +This defines a menu block, see "Menu structure" above for more +information. The only possible options are dependencies and "visible" +attributes. + +if: + + "if" <expr> + <if block> + "endif" + +This defines an if block. The dependency expression <expr> is appended +to all enclosed menu entries. + +source: + + "source" <prompt> + +This reads the specified configuration file. This file is always parsed. + +mainmenu: + + "mainmenu" <prompt> + +This sets the config program's title bar if the config program chooses +to use it. It should be placed at the top of the configuration, before any +other statement. + + +Kconfig hints +------------- +This is a collection of Kconfig tips, most of which aren't obvious at +first glance and most of which have become idioms in several Kconfig +files. + +Adding common features and make the usage configurable +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +It is a common idiom to implement a feature/functionality that are +relevant for some architectures but not all. +The recommended way to do so is to use a config variable named HAVE_* +that is defined in a common Kconfig file and selected by the relevant +architectures. +An example is the generic IOMAP functionality. + +We would in lib/Kconfig see: + +# Generic IOMAP is used to ... +config HAVE_GENERIC_IOMAP + +config GENERIC_IOMAP + depends on HAVE_GENERIC_IOMAP && FOO + +And in lib/Makefile we would see: +obj-$(CONFIG_GENERIC_IOMAP) += iomap.o + +For each architecture using the generic IOMAP functionality we would see: + +config X86 + select ... + select HAVE_GENERIC_IOMAP + select ... + +Note: we use the existing config option and avoid creating a new +config variable to select HAVE_GENERIC_IOMAP. + +Note: the use of the internal config variable HAVE_GENERIC_IOMAP, it is +introduced to overcome the limitation of select which will force a +config option to 'y' no matter the dependencies. +The dependencies are moved to the symbol GENERIC_IOMAP and we avoid the +situation where select forces a symbol equals to 'y'. + +Build as module only +~~~~~~~~~~~~~~~~~~~~ +To restrict a component build to module-only, qualify its config symbol +with "depends on m". E.g.: + +config FOO + depends on BAR && m + +limits FOO to module (=m) or disabled (=n). diff --git a/Documentation/kconfig.txt b/Documentation/kconfig.txt new file mode 100644 index 0000000..bbc99c0 --- /dev/null +++ b/Documentation/kconfig.txt @@ -0,0 +1,237 @@ +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 + make listnewconfig + +and the config program will list any new symbols, one per line. + + 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 + + When searching, symbols are sorted thus: + - first, exact matches, sorted alphabetically (an exact match + is when the search matches the complete symbol name); + - then, other matches, sorted alphabetically. + For example: ^ATH.K matches: + ATH5K ATH9K ATH5K_AHB ATH5K_DEBUG [...] ATH6KL ATH6KL_DEBUG + [...] ATH9K_AHB ATH9K_BTCOEX_SUPPORT ATH9K_COMMON [...] + of which only ATH5K and ATH9K match exactly and so are sorted + first (and in alphabetical order), then come all other symbols, + sorted in alphabetical order. + +______________________________________________________________________ +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. + +### |