kconfig: allow symbols implied by y to become m

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 this feature, Nicolas Pitre, stated that
the 'imply' keyword should not impose any restrictions.
(https://lkml.org/lkml/2020/2/19/714)

I agree, and want to get rid of this tricky behavior.

Suggested-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Nicolas Pitre <nico@fluxnic.net>

diff --git a/Documentation/kbuild/kconfig-language.rst b/Documentation/kbuild/kconfig-language.rst
index d0111dd..d4d988a 100644 (file)
--- 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 8d38b70..b101ef3 100644 (file)
--- 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;