On Mon, 2 Mar 2020, Masahiro Yamada wrote:
> The 'imply' keyword restricts a symbol to y or n, excluding m
> when it is implied by y. This is the original behavior since
> commit 237e3ad0f195 ("Kconfig: Introduce the "imply" keyword").
>
> However, the author of the 'imply' keyword, Nicolas Pitre, stated
> that the 'imply' keyword should not impose any restrictions. [1]
>
> I agree, and want to get rid of this tricky behavior.
>
> [1]: https://lkml.org/lkml/2020/2/19/714
>
> Suggested-by: Nicolas Pitre <nico@xxxxxxxxxxx>
> Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Acked-by: Nicolas Pitre <nico@xxxxxxxxxxx>
In addition to the IS_REACHABLE() note, it might be a good idea to
suggest adding an "imply" reference to the dependency if the feature
provided by BAZ is highli desirable, e.g.:
config FOO
tristate
imply BAR
imply BAZ
> ---
>
> Documentation/kbuild/kconfig-language.rst | 12 +++++++++++-
> scripts/kconfig/symbol.c | 5 +----
> 2 files changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/kbuild/kconfig-language.rst b/Documentation/kbuild/kconfig-language.rst
> index d0111dd26410..d4d988aea679 100644
> --- a/Documentation/kbuild/kconfig-language.rst
> +++ b/Documentation/kbuild/kconfig-language.rst
> @@ -173,7 +173,7 @@ applicable everywhere (see syntax).
> === === ============= ==============
> n y n N/m/y
> m y m M/y/n
> - y y y Y/n
> + y y y Y/m/n
> y n * N
> === === ============= ==============
>
> @@ -181,6 +181,16 @@ applicable everywhere (see syntax).
> ability to hook into a secondary subsystem while allowing the user to
> configure that subsystem out without also having to unset these drivers.
>
> + Note: If the combination of FOO=y and BAR=m causes a link error,
> + you can guard the function call with IS_REACHABLE()::
> +
> + foo_init()
> + {
> + if (IS_REACHABLE(CONFIG_BAZ))
> + baz_register(&foo);
> + ...
> + }
> +
> - limiting menu display: "visible if" <expr>
>
> This attribute is only applicable to menu blocks, if the condition is
> diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
> index 8d38b700b314..b101ef3c377a 100644
> --- a/scripts/kconfig/symbol.c
> +++ b/scripts/kconfig/symbol.c
> @@ -401,8 +401,7 @@ void sym_calc_value(struct symbol *sym)
> sym_warn_unmet_dep(sym);
> newval.tri = EXPR_OR(newval.tri, sym->rev_dep.tri);
> }
> - if (newval.tri == mod &&
> - (sym_get_type(sym) == S_BOOLEAN || sym->implied.tri == yes))
> + if (newval.tri == mod && sym_get_type(sym) == S_BOOLEAN)
> newval.tri = yes;
> break;
> case S_STRING:
> @@ -484,8 +483,6 @@ bool sym_tristate_within_range(struct symbol *sym, tristate val)
> return false;
> if (sym->visible <= sym->rev_dep.tri)
> return false;
> - if (sym->implied.tri == yes && val == mod)
> - return false;
> if (sym_is_choice_value(sym) && sym->visible == yes)
> return val == yes;
> return val >= sym->rev_dep.tri && val <= sym->visible;
> --
> 2.17.1
>
>
