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kconfig: Add support for conditional values

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At present if an optional Kconfig value needs to be used it must be
bracketed by #ifdef. For example, with this Kconfig setup:

config WIBBLE
	bool "Support wibbles, the world needs more wibbles"

config WIBBLE_ADDR
	hex "Address of the wibble"
	depends on WIBBLE

then the following code must be used:

 #ifdef CONFIG_WIBBLE
 static void handle_wibble(void)
 {
 	int val = CONFIG_WIBBLE_ADDR;

	...
 }
 #endif

 static void init_machine()
 {
 ...
 #ifdef CONFIG_WIBBLE
	handle_wibble();
 #endif
 }

Add a new IF_ENABLED_INT() to help with this. So now it is possible to
write, without #ifdefs:

 static void handle_wibble(void)
 {
        int val = IF_ENABLED_INT(CONFIG_WIBBLE, CONFIG_WIBBLE_ADDR);

	...
 }

 static void init_machine()
 {
 ...
 if (IS_ENABLED(CONFIG_WIBBLE))
	handle_wibble();
 }

The value will be CONFIG_WIBBLE_ADDR if CONFIG_WIBBLE is defined and will
produce a build error if not.. This allows us to reduce the use of #ifdef
in the code, ensuring that the compiler still checks the code even if it
is not ultimately used for a particular build.

Add a CONFIG_IF_ENABLED_INT() version as well.

If an attempt is made to use a value that does not exist (i.e. when the
conditional is not enabled), an error about a non-existing function is
generated, e.g.:

common/bloblist.c:447: undefined reference to `invalid_use_of_IF_ENABLED_INT'

Signed-off-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Simon Glass
2022-01-22 05:07:26 -07:00
committed by Tom Rini
parent 310bfa737f
commit 097ff01fb9
2 changed files with 41 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
include/linux/kconfig.h
View File

@@ -57,6 +57,30 @@
*/
#define CONFIG_VAL(option) config_val(option)
/*
* This uses a similar mechanism to config_enabled() above. If cfg is enabled,
* it resolves to the value of opt_cfg, otherwise it resolves to def_val
*/
#define config_opt_enabled(cfg, opt_cfg, def_val) _config_opt_enabled(cfg, opt_cfg, def_val)
#define _config_opt_enabled(cfg_val, opt_value, def_val) \
__config_opt_enabled(__ARG_PLACEHOLDER_##cfg_val, opt_value, def_val)
#define __config_opt_enabled(arg1_or_junk, arg2, def_val) \
___config_opt_enabled(arg1_or_junk arg2, def_val)
#define ___config_opt_enabled(__ignored, val, ...) val
#ifndef __ASSEMBLY__
/*
* Detect usage of a the value when the conditional is not enabled. When used
* in assembly context, this likely produces a assembly error, or hopefully at
* least something recognisable.
*/
long invalid_use_of_IF_ENABLED_INT(void);
#endif
/* Evaluates to int_option if option is defined, otherwise a build error */
#define IF_ENABLED_INT(option, int_option) \
config_opt_enabled(option, int_option, invalid_use_of_IF_ENABLED_INT())
/*
* Count number of arguments to a variadic macro. Currently only need
* it for 1, 2 or 3 arguments.
@@ -111,5 +135,21 @@
#define CONFIG_IS_ENABLED(option, ...) \
__concat(__CONFIG_IS_ENABLED_, __count_args(option, ##__VA_ARGS__)) (option, ##__VA_ARGS__)
#ifndef __ASSEMBLY__
/*
* Detect usage of a the value when the conditional is not enabled. When used
* in assembly context, this likely produces a assembly error, or hopefully at
* least something recognisable.
*/
long invalid_use_of_CONFIG_IF_ENABLED_INT(void);
#endif
/*
* Evaluates to SPL_/TPL_int_option if SPL_/TPL_/option is not defined,
* otherwise build error
*/
#define CONFIG_IF_ENABLED_INT(option, int_option) \
CONFIG_IS_ENABLED(option, (CONFIG_VAL(int_option)), \
(invalid_use_of_CONFIG_IF_ENABLED_INT()))
#endif /* __LINUX_KCONFIG_H */

2
scripts/Makefile.autoconf
View File

@@ -68,7 +68,7 @@ quiet_cmd_u_boot_cfg = CFG $@
cmd_u_boot_cfg = \
$(CPP) $(c_flags) $2 -DDO_DEPS_ONLY -dM $(srctree)/include/common.h > $@.tmp && { \
grep 'define CONFIG_' $@.tmp | \
sed '/define CONFIG_IS_ENABLED(/d;/define CONFIG_VAL(/d;' > $@; \
sed '/define CONFIG_IS_ENABLED(/d;/define CONFIG_IF_ENABLED_INT(/d;/define CONFIG_VAL(/d;' > $@; \
rm $@.tmp; \
} || { \
rm $@.tmp; false; \