That will limit the usefulness but on the other hand avoid
the illegal configurations all over.
+- weak reverse dependencies: "imply" <symbol> ["if" <expr>]
+ This is similar to "select" as it enforces a lower limit on another
+ symbol except that the "implied" symbol's value may still be set to n
+ from a direct dependency or with a visible prompt.
+
+ Given the following example:
+
+ config FOO
+ tristate
+ imply BAZ
+
+ config BAZ
+ tristate
+ depends on BAR
+
+ The following values are possible:
+
+ FOO BAR BAZ's default choice for BAZ
+ --- --- ------------- --------------
+ n y n N/m/y
+ m y m M/y/n
+ y y y Y/n
+ y n * N
+
+ This is useful e.g. with multiple drivers that want to indicate their
+ ability to hook into a secondary subsystem while allowing the user to
+ configure that subsystem out without also having to unset these drivers.
+
- 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
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).
+MODULES is different from 'n'. The comment on the other hand is only
+visible when MODULES is set to 'n'.
Kconfig syntax
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.
+separate list of options. To make sure all the suboptions will really
+show up under the menuconfig entry and not outside of it, every item
+from the <config options> list must depend on the menuconfig symbol.
+In practice, this is achieved by using one of the next two constructs:
+
+(1):
+menuconfig M
+if M
+ config C1
+ config C2
+endif
+
+(2):
+menuconfig M
+config C1
+ depends on M
+config C2
+ depends on M
+
+In the following examples (3) and (4), C1 and C2 still have the M
+dependency, but will not appear under menuconfig M anymore, because
+of C0, which doesn't depend on M:
+
+(3):
+menuconfig M
+ config C0
+if M
+ config C1
+ config C2
+endif
+
+(4):
+menuconfig M
+config C0
+config C1
+ depends on M
+config C2
+ depends on M
choices:
"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.
+options. A choice can only be of type bool or tristate. If no type is
+specified for a choice, it's type will be determined by the type of
+the first choice element in the group or remain unknown if none of the
+choice elements have a type specified, as well.
+
+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
b) Match dependency semantics:
b1) Swap all "select FOO" to "depends on FOO" or,
b2) Swap all "depends on FOO" to "select FOO"
+ c) Consider the use of "imply" instead of "select"
The resolution to a) can be tested with the sample Kconfig file
Documentation/kbuild/Kconfig.recursion-issue-01 through the removal
projects / kconfig-frontends / blobdiff