[PATCH 18/20] Add WARN_ONCE() macro

[Sascha Hauer]

This adds WARN_ONCE from the Linux Kernel. It is useful to warn only
once when we would otherwise spam the log.

Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
 include/asm-generic/bug.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index 8583d2425f..82b78261fc 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -34,4 +34,17 @@
 	unlikely(__ret_warn_on);					\
 })
 #endif
+
+#define WARN_ONCE(condition, format...) ({	\
+	static int __warned;			\
+	int __ret_warn_once = !!(condition);	\
+						\
+	if (unlikely(__ret_warn_once)) {	\
+		if (WARN(!__warned, format)) {	\
+			__warned = 1;		\
+			dump_stack();		\
+		}				\
+	}					\
+	unlikely(__ret_warn_once);		\
+})
 #endif
-- 
2.28.0