[PATCH 02/31] kconfig: Add support for conditional values

[Simon Glass]

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 0 if CONFIG_WIBBLE is not defined, and
CONFIG_WIBBLE_ADDR if it is. 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.

Signed-off-by: Simon Glass <sjg at chromium.org>
---

 include/linux/kconfig.h      | 18 ++++++++++++++++++
 scripts/config_whitelist.txt |  1 +
 2 files changed, 19 insertions(+)

diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h
index a1d1a298426..119c698a158 100644
--- a/include/linux/kconfig.h
+++ b/include/linux/kconfig.h
@@ -59,6 +59,18 @@
  */
 #define CONFIG_VAL(option)  config_val(option)
 
+/* This use a similar mechanism to config_enabled() above */
+#define config_opt_enabled(cfg, opt_cfg) _config_opt_enabled(cfg, opt_cfg)
+#define _config_opt_enabled(cfg_val, opt_value) \
+	__config_opt_enabled(__ARG_PLACEHOLDER_##cfg_val, opt_value)
+#define __config_opt_enabled(arg1_or_junk, arg2) \
+	___config_opt_enabled(arg1_or_junk arg2, 0)
+#define ___config_opt_enabled(__ignored, val, ...) val
+
+/* Evaluates to 0 if option is not defined, int_option if it is defined */
+#define IF_ENABLED_INT(option, int_option) \
+	config_opt_enabled(option, int_option)
+
 /*
  * Count number of arguments to a variadic macro. Currently only need
  * it for 1, 2 or 3 arguments.
@@ -113,5 +125,11 @@
 #define CONFIG_IS_ENABLED(option, ...)					\
 	__concat(__CONFIG_IS_ENABLED_, __count_args(option, ##__VA_ARGS__)) (option, ##__VA_ARGS__)
 
+/*
+ * Evaluates to 0 if SPL_/TPL_/option is not defined, SPL_/TPL_int_option if it
+ * is defined
+ */
+#define CONFIG_IF_ENABLED_INT(option, int_option) \
+	CONFIG_IS_ENABLED(option, (CONFIG_VAL(int_option)), (0))
 
 #endif /* __LINUX_KCONFIG_H */
diff --git a/scripts/config_whitelist.txt b/scripts/config_whitelist.txt
index 022a27288c9..f9d9f4a9cfe 100644
--- a/scripts/config_whitelist.txt
+++ b/scripts/config_whitelist.txt
@@ -609,6 +609,7 @@ CONFIG_ICS307_REFCLK_HZ
 CONFIG_IDE_PREINIT
 CONFIG_IDE_RESET
 CONFIG_IDE_SWAP_IO
+CONFIG_IF_ENABLED_INT
 CONFIG_IMA
 CONFIG_IMX
 CONFIG_IMX6_PWM_PER_CLK
-- 
2.33.1.1089.g2158813163f-goog