kconfig: Clarify choice dependency propagation

It's easy to miss that choices are special-cased to pass on their mode
as the parent dependency.

No functional changes. Only comments added.

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/scripts/kconfig/menu.c b/scripts/kconfig/menu.c
index 7634d567e779..dcf22008b2d6 100644
--- a/scripts/kconfig/menu.c
+++ b/scripts/kconfig/menu.c
@@ -323,6 +323,13 @@ void menu_finalize(struct menu *parent)
                                 if (menu->sym && menu->sym->type == S_UNKNOWN)
                                         menu_set_type(sym->type);
                         }
+
+                        /*
+                         * Use the choice itself as the parent dependency of
+                         * the contained items. This turns the mode of the
+                         * choice into an upper bound on the visibility of the
+                         * choice value symbols.
+                         */
                         parentdep = expr_alloc_symbol(sym);
                 } else if (parent->prompt)
                         parentdep = parent->prompt->visible.expr;