Commit 237e3ad0 authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Thomas Gleixner
Browse files

Kconfig: Introduce the "imply" keyword 



The "imply" keyword is a weak version of "select" where the target
config symbol can still be turned off, avoiding those pitfalls that come
with the "select" keyword.

This is useful e.g. with multiple drivers that want to indicate their
ability to hook into a secondary subsystem while allowing the user to
configure that subsystem out without also having to unset these drivers.

Currently, the same effect can almost be achieved with:

config DRIVER_A
	tristate

config DRIVER_B
	tristate

config DRIVER_C
	tristate

config DRIVER_D
	tristate

[...]

config SUBSYSTEM_X
	tristate
	default DRIVER_A || DRIVER_B || DRIVER_C || DRIVER_D || [...]

This is unwieldy to maintain especially with a large number of drivers.
Furthermore, there is no easy way to restrict the choice for SUBSYSTEM_X
to y or n, excluding m, when some drivers are built-in. The "select"
keyword allows for excluding m, but it excludes n as well. Hence
this "imply" keyword.  The above becomes:

config DRIVER_A
	tristate
	imply SUBSYSTEM_X

config DRIVER_B
	tristate
	imply SUBSYSTEM_X

[...]

config SUBSYSTEM_X
	tristate

This is much cleaner, and way more flexible than "select". SUBSYSTEM_X
can still be configured out, and it can be set as a module when none of
the drivers are configured in or all of them are modular.

Signed-off-by: default avatarNicolas Pitre <nico@linaro.org>
Acked-by: default avatarRichard Cochran <richardcochran@gmail.com>
Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarJohn Stultz <john.stultz@linaro.org>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
Cc: Paul Bolle <pebolle@tiscali.nl>
Cc: linux-kbuild@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: Michal Marek <mmarek@suse.com>
Cc: Edward Cree <ecree@solarflare.com>
Link: http://lkml.kernel.org/r/1478841010-28605-2-git-send-email-nicolas.pitre@linaro.org


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 4b7e9cf9

Documentation/kbuild/kconfig-language.txt

+29 −0
Original line number Diff line number Diff line
@@ -113,6 +113,34 @@ applicable everywhere (see syntax). 
	That will limit the usefulness but on the other hand avoid

	the illegal configurations all over.



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

  This is similar to "select" as it enforces a lower limit on another

  symbol except that the "implied" symbol's value may still be set to n

  from a direct dependency or with a visible prompt.



  Given the following example:



  config FOO

	tristate

	imply BAZ



  config BAZ

	tristate

	depends on BAR



  The following values are possible:



	FOO		BAR		BAZ's default	choice for BAZ

	---		---		-------------	--------------

	n		y		n		N/m/y

	m		y		m		M/y/n

	y		y		y		Y/n

	y		n		*		N



  This is useful e.g. with multiple drivers that want to indicate their

  ability to hook into a secondary subsystem while allowing the user to

  configure that subsystem out without also having to unset these drivers.



- limiting menu display: "visible if" <expr>

  This attribute is only applicable to menu blocks, if the condition is

  false, the menu block is not displayed to the user (the symbols
@@ -481,6 +509,7 @@ historical issues resolved through these different solutions. 
  b) Match dependency semantics:

	b1) Swap all "select FOO" to "depends on FOO" or,

	b2) Swap all "depends on FOO" to "select FOO"

  c) Consider the use of "imply" instead of "select"



The resolution to a) can be tested with the sample Kconfig file

Documentation/kbuild/Kconfig.recursion-issue-01 through the removal

scripts/kconfig/expr.h

+2 −0
Original line number Diff line number Diff line
@@ -85,6 +85,7 @@ struct symbol { 
	struct property *prop;

	struct expr_value dir_dep;

	struct expr_value rev_dep;

	struct expr_value implied;

};



#define for_all_symbols(i, sym) for (i = 0; i < SYMBOL_HASHSIZE; i++) for (sym = symbol_hash[i]; sym; sym = sym->next) if (sym->type != S_OTHER)
@@ -136,6 +137,7 @@ enum prop_type { 
	P_DEFAULT,  /* default y */

	P_CHOICE,   /* choice value */

	P_SELECT,   /* select BAR */

	P_IMPLY,    /* imply BAR */

	P_RANGE,    /* range 7..100 (for a symbol) */

	P_ENV,      /* value from environment variable */

	P_SYMBOL,   /* where a symbol is defined */

scripts/kconfig/menu.c

+39 −16
Original line number Diff line number Diff line
@@ -233,6 +233,8 @@ static void sym_check_prop(struct symbol *sym) 
{

	struct property *prop;

	struct symbol *sym2;

	char *use;



	for (prop = sym->prop; prop; prop = prop->next) {

		switch (prop->type) {

		case P_DEFAULT:
@@ -252,18 +254,20 @@ static void sym_check_prop(struct symbol *sym) 
			}

			break;

		case P_SELECT:

		case P_IMPLY:

			use = prop->type == P_SELECT ? "select" : "imply";

			sym2 = prop_get_symbol(prop);

			if (sym->type != S_BOOLEAN && sym->type != S_TRISTATE)

				prop_warn(prop,

				    "config symbol '%s' uses select, but is "

				    "not boolean or tristate", sym->name);

				    "config symbol '%s' uses %s, but is "

				    "not boolean or tristate", sym->name, use);

			else if (sym2->type != S_UNKNOWN &&

				 sym2->type != S_BOOLEAN &&

				 sym2->type != S_TRISTATE)

				prop_warn(prop,

				    "'%s' has wrong type. 'select' only "

				    "'%s' has wrong type. '%s' only "

				    "accept arguments of boolean and "

				    "tristate type", sym2->name);

				    "tristate type", sym2->name, use);

			break;

		case P_RANGE:

			if (sym->type != S_INT && sym->type != S_HEX)
@@ -333,6 +337,10 @@ void menu_finalize(struct menu *parent) 
					struct symbol *es = prop_get_symbol(prop);

					es->rev_dep.expr = expr_alloc_or(es->rev_dep.expr,

							expr_alloc_and(expr_alloc_symbol(menu->sym), expr_copy(dep)));

				} else if (prop->type == P_IMPLY) {

					struct symbol *es = prop_get_symbol(prop);

					es->implied.expr = expr_alloc_or(es->implied.expr,

							expr_alloc_and(expr_alloc_symbol(menu->sym), expr_copy(dep)));

				}

			}

		}
@@ -612,13 +620,30 @@ static struct property *get_symbol_prop(struct symbol *sym) 
	return prop;

}



static void get_symbol_props_str(struct gstr *r, struct symbol *sym,

				 enum prop_type tok, const char *prefix)

{

	bool hit = false;

	struct property *prop;



	for_all_properties(sym, prop, tok) {

		if (!hit) {

			str_append(r, prefix);

			hit = true;

		} else

			str_printf(r, " && ");

		expr_gstr_print(prop->expr, r);

	}

	if (hit)

		str_append(r, "\n");

}



/*

 * head is optional and may be NULL

 */

static void get_symbol_str(struct gstr *r, struct symbol *sym,

		    struct list_head *head)

{

	bool hit;

	struct property *prop;



	if (sym && sym->name) {
@@ -648,22 +673,20 @@ static void get_symbol_str(struct gstr *r, struct symbol *sym, 
		}

	}



	hit = false;

	for_all_properties(sym, prop, P_SELECT) {

		if (!hit) {

			str_append(r, "  Selects: ");

			hit = true;

		} else

			str_printf(r, " && ");

		expr_gstr_print(prop->expr, r);

	}

	if (hit)

		str_append(r, "\n");

	get_symbol_props_str(r, sym, P_SELECT, _("  Selects: "));

	if (sym->rev_dep.expr) {

		str_append(r, _("  Selected by: "));

		expr_gstr_print(sym->rev_dep.expr, r);

		str_append(r, "\n");

	}



	get_symbol_props_str(r, sym, P_IMPLY, _("  Implies: "));

	if (sym->implied.expr) {

		str_append(r, _("  Implied by: "));

		expr_gstr_print(sym->implied.expr, r);

		str_append(r, "\n");

	}



	str_append(r, "\n\n");

}

scripts/kconfig/symbol.c

+23 −1
Original line number Diff line number Diff line
@@ -258,6 +258,15 @@ static void sym_calc_visibility(struct symbol *sym) 
		sym->rev_dep.tri = tri;

		sym_set_changed(sym);

	}

	tri = no;

	if (sym->implied.expr && sym->dir_dep.tri != no)

		tri = expr_calc_value(sym->implied.expr);

	if (tri == mod && sym_get_type(sym) == S_BOOLEAN)

		tri = yes;

	if (sym->implied.tri != tri) {

		sym->implied.tri = tri;

		sym_set_changed(sym);

	}

}



/*
@@ -397,6 +406,10 @@ void sym_calc_value(struct symbol *sym) 
					newval.tri = EXPR_AND(expr_calc_value(prop->expr),

							      prop->visible.tri);

				}

				if (sym->implied.tri != no) {

					sym->flags |= SYMBOL_WRITE;

					newval.tri = EXPR_OR(newval.tri, sym->implied.tri);

				}

			}

		calc_newval:

			if (sym->dir_dep.tri == no && sym->rev_dep.tri != no) {
@@ -413,7 +426,8 @@ void sym_calc_value(struct symbol *sym) 
			}

			newval.tri = EXPR_OR(newval.tri, sym->rev_dep.tri);

		}

		if (newval.tri == mod && sym_get_type(sym) == S_BOOLEAN)

		if (newval.tri == mod &&

		    (sym_get_type(sym) == S_BOOLEAN || sym->implied.tri == yes))

			newval.tri = yes;

		break;

	case S_STRING:
@@ -498,6 +512,8 @@ 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;
@@ -750,6 +766,10 @@ const char *sym_get_string_default(struct symbol *sym) 
	if (sym->type == S_BOOLEAN && val == mod)

		val = yes;



	/* adjust the default value if this symbol is implied by another */

	if (val < sym->implied.tri)

		val = sym->implied.tri;



	switch (sym->type) {

	case S_BOOLEAN:

	case S_TRISTATE:
@@ -1352,6 +1372,8 @@ const char *prop_get_type_name(enum prop_type type) 
		return "choice";

	case P_SELECT:

		return "select";

	case P_IMPLY:

		return "imply";

	case P_RANGE:

		return "range";

	case P_SYMBOL:

scripts/kconfig/zconf.gperf

+1 −0
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ int, T_TYPE, TF_COMMAND, S_INT 
hex,		T_TYPE,		TF_COMMAND, S_HEX

string,		T_TYPE,		TF_COMMAND, S_STRING

select,		T_SELECT,	TF_COMMAND

imply,		T_IMPLY,	TF_COMMAND

range,		T_RANGE,	TF_COMMAND

visible,	T_VISIBLE,	TF_COMMAND

option,		T_OPTION,	TF_COMMAND

CRA Git | Maintained and supported by SUSTech CRA and CCSE