vsprintf: Recursive vsnprintf: Add "%pV", struct va_format

Add the ability to print a format and va_list from a structure pointer

Allows __dev_printk to be implemented as a single printk while
minimizing string space duplication.

%pV should not be used without some mechanism to verify the
format and argument use ala __attribute__(format (printf(...))).

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 8317ec4..01dfc05 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -171,6 +171,11 @@
 }
 #endif
 
+struct va_format {
+	const char *fmt;
+	va_list *va;
+};
+
 extern struct atomic_notifier_head panic_notifier_list;
 extern long (*panic_blink)(long time);
 NORET_TYPE void panic(const char * fmt, ...)