From 89f586e5b3a22a6364d83f18504ba1aeb4bbdebb Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <djwong@us.ibm.com>
Date: Fri, 23 Mar 2012 15:02:26 -0700
Subject: [PATCH] --- yaml --- r: 295228 b: refs/heads/master c:
 5cde7656d0dd222170eb0250bd1f70c9018fd438 h: refs/heads/master v: v3

---
 [refs]                |  2 +-
 trunk/lib/Kconfig     | 43 +++++++++++++++++++++++++++++++++++++++++++
 trunk/lib/crc32defs.h | 18 ++++++++++++++++++
 3 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 3ae8121ea5d7..9354a7335158 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 577eba9e22e872574c466648b46eeb3e0d04372e
+refs/heads/master: 5cde7656d0dd222170eb0250bd1f70c9018fd438
diff --git a/trunk/lib/Kconfig b/trunk/lib/Kconfig
index 6d7ce4b138c4..43359bb1ca90 100644
--- a/trunk/lib/Kconfig
+++ b/trunk/lib/Kconfig
@@ -80,6 +80,49 @@ config CRC32_SELFTEST
 	  and crc32_be over byte strings with random alignment and length
 	  and computes the total elapsed time and number of bytes processed.
 
+choice
+	prompt "CRC32 implementation"
+	depends on CRC32
+	default CRC32_SLICEBY8
+
+config CRC32_SLICEBY8
+	bool "Slice by 8 bytes"
+	help
+	  Calculate checksum 8 bytes at a time with a clever slicing algorithm.
+	  This is the fastest algorithm, but comes with a 8KiB lookup table.
+	  Most modern processors have enough cache to hold this table without
+	  thrashing the cache.
+
+	  This is the default implementation choice.  Choose this one unless
+	  you have a good reason not to.
+
+config CRC32_SLICEBY4
+	bool "Slice by 4 bytes"
+	help
+	  Calculate checksum 4 bytes at a time with a clever slicing algorithm.
+	  This is a bit slower than slice by 8, but has a smaller 4KiB lookup
+	  table.
+
+	  Only choose this option if you know what you are doing.
+
+config CRC32_SARWATE
+	bool "Sarwate's Algorithm (one byte at a time)"
+	help
+	  Calculate checksum a byte at a time using Sarwate's algorithm.  This
+	  is not particularly fast, but has a small 256 byte lookup table.
+
+	  Only choose this option if you know what you are doing.
+
+config CRC32_BIT
+	bool "Classic Algorithm (one bit at a time)"
+	help
+	  Calculate checksum one bit at a time.  This is VERY slow, but has
+	  no lookup table.  This is provided as a debugging option.
+
+	  Only choose this option if you are debugging crc32.
+
+endchoice
+
 config CRC7
 	tristate "CRC7 functions"
 	help
diff --git a/trunk/lib/crc32defs.h b/trunk/lib/crc32defs.h
index 6fd191732fec..64cba2c3c700 100644
--- a/trunk/lib/crc32defs.h
+++ b/trunk/lib/crc32defs.h
@@ -13,6 +13,24 @@
  */
 #define CRC32C_POLY_LE 0x82F63B78
 
+/* Try to choose an implementation variant via Kconfig */
+#ifdef CONFIG_CRC32_SLICEBY8
+# define CRC_LE_BITS 64
+# define CRC_BE_BITS 64
+#endif
+#ifdef CONFIG_CRC32_SLICEBY4
+# define CRC_LE_BITS 32
+# define CRC_BE_BITS 32
+#endif
+#ifdef CONFIG_CRC32_SARWATE
+# define CRC_LE_BITS 8
+# define CRC_BE_BITS 8
+#endif
+#ifdef CONFIG_CRC32_BIT
+# define CRC_LE_BITS 1
+# define CRC_BE_BITS 1
+#endif
+
 /*
  * How many bits at a time to use.  Valid values are 1, 2, 4, 8, 32 and 64.
  * For less performance-sensitive, use 4 or 8 to save table size.