Add a dummy printk function for the maintenance of unused printks

Add a dummy printk function for the maintenance of unused printks through gcc
format checking, and also so that side-effect checking is maintained too.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/kernel.h

@@ -306,6 +306,13 @@ static inline void log_buf_kexec_setup(void)
 }
 #endif
 
+/*
+ * Dummy printk for disabled debugging statements to use whilst maintaining
+ * gcc's format and side-effect checking.
+ */
+static inline __attribute__ ((format (printf, 1, 2)))
+int no_printk(const char *s, ...) { return 0; }
+
 extern int printk_needs_cpu(int cpu);
 extern void printk_tick(void);