diff options
Diffstat (limited to 'Documentation/kbuild/kconfig-language.txt')
| -rw-r--r-- | Documentation/kbuild/kconfig-language.txt | 44 |
1 files changed, 36 insertions, 8 deletions
diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt index 262722d8867b..f5b9493f04ad 100644 --- a/Documentation/kbuild/kconfig-language.txt +++ b/Documentation/kbuild/kconfig-language.txt @@ -77,6 +77,27 @@ applicable everywhere (see syntax). Optionally, dependencies only for this default value can be added with "if". + The default value deliberately defaults to 'n' in order to avoid bloating the + build. With few exceptions, new config options should not change this. The + intent is for "make oldconfig" to add as little as possible to the config from + release to release. + + Note: + Things that merit "default y/m" include: + + a) A new Kconfig option for something that used to always be built + should be "default y". + + b) A new gatekeeping Kconfig option that hides/shows other Kconfig + options (but does not generate any code of its own), should be + "default y" so people will see those other options. + + c) Sub-driver behavior or similar options for a driver that is + "default n". This allows you to provide sane defaults. + + d) Hardware or infrastructure that everybody expects, such as CONFIG_NET + or CONFIG_BLOCK. These are rare exceptions. + - type definition + default value: "def_bool"/"def_tristate" <expr> ["if" <expr>] This is a shorthand notation for a type definition plus a value. @@ -200,10 +221,14 @@ 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) + <symbol1> '<' <symbol2> (4) + <symbol1> '>' <symbol2> (4) + <symbol1> '<=' <symbol2> (4) + <symbol1> '>=' <symbol2> (4) + '(' <expr> ')' (5) + '!' <expr> (6) + <expr> '&&' <expr> (7) + <expr> '||' <expr> (8) Expressions are listed in decreasing order of precedence. @@ -214,10 +239,13 @@ Expressions are listed in decreasing order of precedence. 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/). +(4) If value of <symbol1> is respectively lower, greater, lower-or-equal, + or greater-or-equal than value of <symbol2>, it returns 'y', + otherwise 'n'. +(5) Returns the value of the expression. Used to override precedence. +(6) Returns the result of (2-/expr/). +(7) Returns the result of min(/expr/, /expr/). +(8) 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 |