Unverified Commit 76df6815 authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Nathan Chancellor
Browse files

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: default avatarNicolas Pitre <nico@fluxnic.net>
[Graham Roff: Rewrote commit message, updated patch, added tests]
Signed-off-by: default avatarGraham Roff <grahamr@qti.qualcomm.com>
Acked-by: default avatarRandy 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: default avatarNathan Chancellor <nathan@kernel.org>
parent 5ce3218d

Documentation/kbuild/kconfig-language.rst

+19 −3
Original line number Diff line number Diff line
@@ -118,7 +118,7 @@ applicable everywhere (see syntax). 
  This is a shorthand notation for a type definition plus a value.

  Optionally dependencies for this default value can be added with "if".



- dependencies: "depends on" <expr>

- dependencies: "depends on" <expr> ["if" <expr>]



  This defines a dependency for this menu entry. If multiple

  dependencies are defined, they are connected with '&&'. Dependencies
@@ -134,6 +134,16 @@ applicable everywhere (see syntax). 
	bool "foo"

	default y



  The dependency definition itself may be conditional by appending "if"

  followed by an expression. For example::



    config FOO

	tristate

	depends on BAR if BAZ



  meaning that FOO is constrained by the value of BAR only if BAZ is

  also set.



- reverse dependencies: "select" <symbol> ["if" <expr>]



  While normal dependencies reduce the upper limit of a symbol (see
@@ -602,8 +612,14 @@ Some drivers are able to optionally use a feature from another module 
or build cleanly with that module disabled, but cause a link failure

when trying to use that loadable module from a built-in driver.



The most common way to express this optional dependency in Kconfig logic

uses the slightly counterintuitive::

The recommended way to express this optional dependency in Kconfig logic

uses the conditional form::



  config FOO

	tristate "Support for foo hardware"

	depends on BAR if BAR



This slightly counterintuitive style is also widely used::



  config FOO

	tristate "Support for foo hardware"

scripts/kconfig/lkc.h

+1 −1
Original line number Diff line number Diff line
@@ -82,7 +82,7 @@ void menu_warn(const struct menu *menu, const char *fmt, ...); 
struct menu *menu_add_menu(void);

void menu_end_menu(void);

void menu_add_entry(struct symbol *sym, enum menu_type type);

void menu_add_dep(struct expr *dep);

void menu_add_dep(struct expr *dep, struct expr *cond);

void menu_add_visibility(struct expr *dep);

struct property *menu_add_prompt(enum prop_type type, const char *prompt,

				 struct expr *dep);

scripts/kconfig/menu.c

+11 −1
Original line number Diff line number Diff line
@@ -127,8 +127,18 @@ static struct expr *rewrite_m(struct expr *e) 
	return e;

}



void menu_add_dep(struct expr *dep)

void menu_add_dep(struct expr *dep, struct expr *cond)

{

	if (cond) {

		/*

		 * We have "depends on X if Y" and we want:

		 *	Y != n --> X

		 *	Y == n --> y

		 * That simplifies to: (X || (Y == n))

		 */

		dep = expr_alloc_or(dep,

				expr_trans_compare(cond, E_EQUAL, &symbol_no));

	}

	current_entry->dep = expr_alloc_and(current_entry->dep, dep);

}

scripts/kconfig/parser.y

+3 −3
Original line number Diff line number Diff line
@@ -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);

};

scripts/kconfig/tests/conditional_dep/Kconfig

0 → 100644
+32 −0
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0

# Test Kconfig file for conditional dependencies.



# Enable module support for tristate testing

config MODULES

	bool "Enable loadable module support"

	modules

	default y



config FOO

	bool "FOO symbol"



config BAR

	bool "BAR symbol"



config TEST_BASIC

	bool "Test basic conditional dependency"

	depends on FOO if BAR

	default y



config TEST_COMPLEX

	bool "Test complex conditional dependency"

	depends on (FOO && BAR) if (FOO || BAR)

	default y



config BAZ

	tristate "BAZ symbol"



config TEST_OPTIONAL

	tristate "Test simple optional dependency"

	depends on BAZ if BAZ

	default y