ARM处理器的IP软核

Introduction ------------ The configuration database is 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 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"/"integer" 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". - dependencies: "depends on"/"requires" <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. - numerical ranges: "range" <symbol> <symbol> ["if" <expr>] This allows to limit the range of possible input values for integer 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 seperate configuration logic from help within the file as an aid to developers. 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 max(/expr/, /expr/). (7) Returns the result of min(/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 it's expression evaluates to 'm' or 'y'. There are two types of symbols: constant and nonconstant symbols. Nonconstant symbols are the most common ones and are defined with the 'config' statement. Nonconstant 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 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 MODULES comment "module support disabled" depends !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 hel