The macro filters out printk messages based on a configurable verbosity level (CONFIG_PRINTK_VERBOSITY).
Signed-off-by: Marc Andre Tanner <m...@brain-dump.org> --- include/linux/kernel.h | 24 ++++++++++++++++++++++++ 1 files changed, 24 insertions(+), 0 deletions(-) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index c2b3047..1f5d01f 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -242,6 +242,30 @@ asmlinkage int printk(const char * fmt, ...) asmlinkage int printk_unfiltered(const char *fmt, ...) __attribute__ ((format (printf, 1, 2))) __cold; +#if defined(CONFIG_PRINTK_VERBOSITY) && CONFIG_PRINTK_VERBOSITY > 0 +/* + * The idea here is to wrap the actual printk function with a macro which + * will filter out all messages above a certain verbosity level. Because + * the if condition evaluates to a constant expression the compiler will be + * able to eliminate it and the resulting kernel image will be smaller. + * + * The check with sizeof(void*) should make sure that we don't operate on + * pointers, which the compiler wouldn't be able to optimize out, but only + * on string constants. + */ + +#include <linux/stringify.h> + +#define printk(fmt, ...) ({ \ + if (sizeof(fmt) == sizeof(void *) || \ + (((const char *)(fmt))[0] != '<' && CONFIG_PRINTK_VERBOSITY >= 4) || \ + (((const char *)(fmt))[0] == '<' && \ + ((const char *)(fmt))[1] <= *__stringify(CONFIG_PRINTK_VERBOSITY))) \ + printk((fmt), ##__VA_ARGS__); \ +}) + +#endif /* CONFIG_PRINTK_VERBOSITY */ + extern struct ratelimit_state printk_ratelimit_state; extern int printk_ratelimit(void); extern bool printk_timed_ratelimit(unsigned long *caller_jiffies, -- 1.6.3.3 -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html