diff options
Diffstat (limited to 'extra/config/kconfig-language.txt')
| -rw-r--r-- | extra/config/kconfig-language.txt | 41 |
1 files changed, 9 insertions, 32 deletions
diff --git a/extra/config/kconfig-language.txt b/extra/config/kconfig-language.txt index 649cb8799..c412c2458 100644 --- a/extra/config/kconfig-language.txt +++ b/extra/config/kconfig-language.txt @@ -104,14 +104,15 @@ applicable everywhere (see syntax). Reverse dependencies can only be used with boolean or tristate symbols. Note: - select is evil.... select will by brute force set a symbol - equal to 'y' without visiting the dependencies. So 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. kconfig - should one day warn about such things. + 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. + kconfig should one day warn about such things. - numerical ranges: "range" <symbol> <symbol> ["if" <expr>] This allows to limit the range of possible input values for int @@ -376,27 +377,3 @@ config FOO limits FOO to module (=m) or disabled (=n). - -Build limited by a third config symbol which may be =y or =m -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -A common idiom that we see (and sometimes have problems with) is this: - -When option C in B (module or subsystem) uses interfaces from A (module -or subsystem), and both A and B are tristate (could be =y or =m if they -were independent of each other, but they aren't), then we need to limit -C such that it cannot be built statically if A is built as a loadable -module. (C already depends on B, so there is no dependency issue to -take care of here.) - -If A is linked statically into the kernel image, C can be built -statically or as loadable module(s). However, if A is built as loadable -module(s), then C must be restricted to loadable module(s) also. This -can be expressed in kconfig language as: - -config C - depends on A = y || A = B - -or for real examples, use this command in a kernel tree: - -$ find . -name Kconfig\* | xargs grep -ns "depends on.*=.*||.*=" | grep -v orig - |