The -Wmaybe-uninitialized warning triggers for one driver using the output
of the 'insb' I/O helper on x86:

drivers/net/wireless/wl3501_cs.c: In function ‘wl3501_mgmt_scan_confirm’:
drivers/net/wireless/wl3501_cs.c:665:9: error: ‘sig.status’ is used 
uninitialized in this function [-Werror=uninitialized]
drivers/net/wireless/wl3501_cs.c:668:12: error: ‘sig.cap_info’ may be used 
uninitialized in this function [-Werror=maybe-uninitialized]

Apparently the assember constraints are slightly off here, as marking the
'addr' argument as a memory output seems appropriate here and gets rid
of the warning. For consistency I'm also adding it as input for outsb().

I'm not an x86 person and gcc inline assembly mystifies me all the time,
so please review this carefully and suggest a better way if this is not
how it should be done.

Signed-off-by: Arnd Bergmann <>
 arch/x86/include/asm/io.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index de25aad..287234c 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -304,13 +304,13 @@ static inline unsigned type in##bwl##_p(int port)         
 static inline void outs##bwl(int port, const void *addr, unsigned long count) \
 {                                                                      \
        asm volatile("rep; outs" #bwl                                   \
-                    : "+S"(addr), "+c"(count) : "d"(port));            \
+                    : "+S"(addr), "+c"(count) : "d"(port), "m" (addr));\
 }                                                                      \
 static inline void ins##bwl(int port, void *addr, unsigned long count) \
 {                                                                      \
        asm volatile("rep; ins" #bwl                                    \
-                    : "+D"(addr), "+c"(count) : "d"(port));            \
+                    : "+D"(addr), "+c"(count), "=m" (addr) : "d"(port));\
 BUILDIO(b, b, char)

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