kconfig: Support conditional deps using "depends on X if Y"

Extend the "depends on" syntax to support conditional dependencies
using "depends on X if Y". While functionally equivalent to "depends
on X || (Y == n)", "depends on X if Y" is much more readable and
makes the kconfig language uniform in supporting the "if <expr>"
suffix.
This also improves readability for "optional" dependencies, which
are the subset of conditional dependencies where X is Y.
Previously such optional dependencies had to be expressed as
the counterintuitive "depends on X || !X", now this can be
represented as "depends on X if X".

The change is implemented by converting the "X if Y" syntax into the
"X || (Y == n)" syntax during "depends on" token processing.

Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
[Graham Roff: Rewrote commit message, updated patch, added tests]
Signed-off-by: Graham Roff <grahamr@qti.qualcomm.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://patch.msgid.link/20251215-kconfig_conditional_deps-v3-1-59519af0a5df@qti.qualcomm.com
[nathan: Minor adjustments to spacing]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/scripts/kconfig/parser.y b/scripts/kconfig/parser.y
index 49b79dde1725..6d1bbee38f5d 100644
--- a/scripts/kconfig/parser.y
+++ b/scripts/kconfig/parser.y
@@ -323,7 +323,7 @@ if_entry: T_IF expr T_EOL
 {
 	printd(DEBUG_PARSE, "%s:%d:if\n", cur_filename, cur_lineno);
 	menu_add_entry(NULL, M_IF);
-	menu_add_dep($2);
+	menu_add_dep($2, NULL);
 	$$ = menu_add_menu();
 };
 
@@ -422,9 +422,9 @@ help: help_start T_HELPTEXT
 
 /* depends option */
 
-depends: T_DEPENDS T_ON expr T_EOL
+depends: T_DEPENDS T_ON expr if_expr T_EOL
 {
-	menu_add_dep($3);
+	menu_add_dep($3, $4);
 	printd(DEBUG_PARSE, "%s:%d:depends on\n", cur_filename, cur_lineno);
 };