[PATCH] compiler: add support for fallthrough attribute

[Ahmad Fatoum]

Use of it is enforced in Linux now, so code we'll port may contain it.
Import the definition.

Signed-off-by: Ahmad Fatoum <ahmad at a3f.at>
---
 include/linux/compiler_types.h | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index aa9cbcac7740..bc1b43aab0dc 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -112,6 +112,27 @@ struct ftrace_likely_data {
 #define __deprecated
 #define __deprecated_for_modules
 
+#ifndef __has_attribute
+#define __has_attribute(...)		0
+#endif
+
+/*
+ * Add the pseudo keyword 'fallthrough' so case statement blocks
+ * must end with any of these keywords:
+ *   break;
+ *   fallthrough;
+ *   continue;
+ *   goto <label>;
+ *   return [expression];
+ *
+ *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
+ */
+#if __has_attribute(__fallthrough__)
+# define fallthrough                    __attribute__((__fallthrough__))
+#else
+# define fallthrough                    do {} while (0)  /* fallthrough */
+#endif
+
 #endif /* __KERNEL__ */
 
 #endif /* __ASSEMBLY__ */
-- 
2.34.1