lib: import bitrev library from the linux kernel

This patch adds the bitrev library from the linux kernel.  This is a simple
algorithm that uses an 8 bit look-up table to reverse the bits in data types of
8, 16, or 32 bit widths.  The docg4 nand flash driver uses it.

[port from linux kernel v3.9 commit 7ee32a6d30d1c8a3b7a07a6269da8f0a08662927]
[originally added: v2.6.20 by commit a5cfc1ec58a07074dacb6aa8c79eff864c966d12]

Signed-off-by: Mike Dunn <mikedunn@newsguy.com>

include/linux/bitrev.h

@@ -0,0 +1,23 @@
+/*
+ * This file is released under the terms of GPL v2 and any later version.
+ * See the file COPYING in the root directory of the source tree for details.
+ *
+ * Based on bitrev from the Linux kernel, by Akinobu Mita
+ */
+
+#ifndef _LINUX_BITREV_H
+#define _LINUX_BITREV_H
+
+#include <linux/types.h>
+
+extern u8 const byte_rev_table[256];
+
+static inline u8 bitrev8(u8 byte)
+{
+	return byte_rev_table[byte];
+}
+
+u16 bitrev16(u16 in);
+u32 bitrev32(u32 in);
+
+#endif /* _LINUX_BITREV_H */

lib/Makefile

@@ -55,6 +55,7 @@ COBJS-$(CONFIG_SHA256) += sha256.o
 COBJS-y	+= strmhz.o
 COBJS-$(CONFIG_TPM) += tpm.o
 COBJS-$(CONFIG_RBTREE)	+= rbtree.o
+COBJS-$(CONFIG_BITREVERSE) += bitrev.o
 endif
 
 ifdef CONFIG_SPL_BUILD

lib/bitrev.c

@@ -0,0 +1,59 @@
+/*
+ * This file is released under the terms of GPL v2 and any later version.
+ * See the file COPYING in the root directory of the source tree for details.
+ *
+ * Based on bitrev from the Linux kernel, by Akinobu Mita
+ */
+
+
+#include <linux/types.h>
+#include <linux/bitrev.h>
+
+const u8 byte_rev_table[256] = {
+	0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,
+	0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
+	0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8,
+	0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
+	0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4,
+	0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
+	0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec,
+	0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
+	0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2,
+	0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
+	0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea,
+	0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
+	0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6,
+	0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
+	0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee,
+	0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
+	0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1,
+	0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
+	0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9,
+	0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
+	0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5,
+	0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
+	0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed,
+	0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
+	0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3,
+	0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
+	0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb,
+	0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
+	0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7,
+	0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
+	0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,
+	0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff,
+};
+
+u16 bitrev16(u16 x)
+{
+	return (bitrev8(x & 0xff) << 8) | bitrev8(x >> 8);
+}
+
+/**
+ * bitrev32 - reverse the order of bits in a u32 value
+ * @x: value to be bit-reversed
+ */
+u32 bitrev32(u32 x)
+{
+	return (bitrev16(x & 0xffff) << 16) | bitrev16(x >> 16);
+}