arm: introduce asm/swab.h

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 50 insertions, 0 deletions

diff --git a/arch/arm/include/asm/swab.h b/arch/arm/include/asm/swab.h
new file mode 100644
index 000000000000..27a689be0856
--- /dev/null
+++ b/arch/arm/include/asm/swab.h
@@ -0,0 +1,50 @@
+/*
+ *  arch/arm/include/asm/byteorder.h
+ *
+ * ARM Endian-ness.  In little endian mode, the data bus is connected such
+ * that byte accesses appear as:
+ *  0 = d0...d7, 1 = d8...d15, 2 = d16...d23, 3 = d24...d31
+ * and word accesses (data or instruction) appear as:
+ *  d0...d31
+ *
+ * When in big endian mode, byte accesses appear as:
+ *  0 = d24...d31, 1 = d16...d23, 2 = d8...d15, 3 = d0...d7
+ * and word accesses (data or instruction) appear as:
+ *  d0...d31
+ */
+#ifndef __ASM_ARM_SWAB_H
+#define __ASM_ARM_SWAB_H
+
+#include <linux/compiler.h>
+#include <asm/types.h>
+
+#if !defined(__STRICT_ANSI__) || defined(__KERNEL__)
+#  define __SWAB_64_THRU_32__
+#endif
+
+static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
+{
+	__u32 t;
+
+#ifndef __thumb__
+	if (!__builtin_constant_p(x)) {
+		/*
+		 * The compiler needs a bit of a hint here to always do the
+		 * right thing and not screw it up to different degrees
+		 * depending on the gcc version.
+		 */
+		asm ("eor\t%0, %1, %1, ror #16" : "=r" (t) : "r" (x));
+	} else
+#endif
+		t = x ^ ((x << 16) | (x >> 16)); /* eor r1,r0,r0,ror #16 */
+
+	x = (x << 24) | (x >> 8);		/* mov r0,r0,ror #8      */
+	t &= ~0x00FF0000;			/* bic r1,r1,#0x00FF0000 */
+	x ^= (t >> 8);				/* eor r0,r0,r1,lsr #8   */
+
+	return x;
+}
+#define __arch_swab32 __arch_swab32
+
+#endif
+