Add a function to reverse bytes within a 32 bit word.
This function is more efficient than using the 8 bit version when
iterating over an array

Signed-off-by: Joshua Clayton <stillcompil...@gmail.com>
---

Looking for an ACK from Russell King on this patch (or at least 
the arm specific implementation)

 arch/arm/include/asm/bitrev.h |  5 +++++
 include/linux/bitrev.h        | 26 ++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/arch/arm/include/asm/bitrev.h b/arch/arm/include/asm/bitrev.h
index ec291c3..6d2e9ca 100644
--- a/arch/arm/include/asm/bitrev.h
+++ b/arch/arm/include/asm/bitrev.h
@@ -17,4 +17,9 @@ static __always_inline __attribute_const__ u8 
__arch_bitrev8(u8 x)
        return __arch_bitrev32((u32)x) >> 24;
 }
 
+static __always_inline __attribute_const__ u32 __arch_bitrev8x4(u32 x)
+{
+       __asm__ ("rbit %0, %1; rev %0, %0" : "=r" (x) : "r" (x));
+}
+
 #endif
diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h
index fb790b8..b1cfa1a 100644
--- a/include/linux/bitrev.h
+++ b/include/linux/bitrev.h
@@ -9,6 +9,7 @@
 #define __bitrev32 __arch_bitrev32
 #define __bitrev16 __arch_bitrev16
 #define __bitrev8 __arch_bitrev8
+#define __bitrev8x4 __arch_bitrev8x4
 
 #else
 extern u8 const byte_rev_table[256];
@@ -27,6 +28,14 @@ static inline u32 __bitrev32(u32 x)
        return (__bitrev16(x & 0xffff) << 16) | __bitrev16(x >> 16);
 }
 
+static inline u32 __bitrev8x4(u32 x)
+{
+       return(__bitrev8(x & 0xff) |
+              (__bitrev8((x >> 8)  & 0xff) << 8) |
+              (__bitrev8((x >> 16)  & 0xff) << 16) |
+              (__bitrev8((x >> 24)  & 0xff) << 24));
+}
+
 #endif /* CONFIG_HAVE_ARCH_BITREVERSE */
 
 #define __constant_bitrev32(x) \
@@ -50,6 +59,15 @@ static inline u32 __bitrev32(u32 x)
        __x;                                                            \
 })
 
+#define __constant_bitrev8x4(x) \
+({                     \
+       u32 __x = x;    \
+       __x = ((__x & (u32)0xF0F0F0F0UL) >> 4) | ((__x & (u32)0x0F0F0F0FUL) << 
4);      \
+       __x = ((__x & (u32)0xCCCCCCCCUL) >> 2) | ((__x & (u32)0x33333333UL) << 
2);      \
+       __x = ((__x & (u32)0xAAAAAAAAUL) >> 1) | ((__x & (u32)0x55555555UL) << 
1);      \
+       __x;                                                            \
+})
+
 #define __constant_bitrev8(x)  \
 ({                                     \
        u8 __x = x;                     \
@@ -75,6 +93,14 @@ static inline u32 __bitrev32(u32 x)
        __bitrev16(__x);                                \
  })
 
+#define bitrev8x4(x) \
+({                     \
+       u32 __x = x;    \
+       __builtin_constant_p(__x) ?     \
+       __constant_bitrev8x4(__x) :                     \
+       __bitrev8x4(__x);                               \
+})
+
 #define bitrev8(x) \
 ({                     \
        u8 __x = x;     \
-- 
2.9.3

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