[U-Boot] [PATCH 2/2] Roll CRC16-CCITT into the hash infrastructure

[Philipp Tomsich]

The CRC16-CCITT checksum function is useful for space-constrained
applications (such as obtaining a checksum across a 2KBit or 4KBit
EEPROM) in boot applications. It has not been accessible from boot
scripts until now (due to not having a dedicated command and not being
supported by the hash infrstructure) limiting its applicability
outside of custom commands.

This adds the CRC16-CCITT (poly 0x1021, init 0x0) algorithm to the
list of available hashes and adds a new crc16_ccitt_wd_buf() to make
this possible.

Signed-off-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
---

 common/hash.c        | 36 ++++++++++++++++++++++++++++++++++++
 include/u-boot/crc.h | 11 +++++++++++
 lib/crc16.c          | 23 +++++++++++++++++------
 tools/Makefile       |  1 +
 4 files changed, 65 insertions(+), 6 deletions(-)

diff --git a/common/hash.c b/common/hash.c
index ef14651..413a5bf 100644
--- a/common/hash.c
+++ b/common/hash.c
@@ -85,6 +85,33 @@ static int hash_finish_sha256(struct hash_algo *algo, void *ctx, void
 }
 #endif
 
+static int hash_init_crc16_ccitt(struct hash_algo *algo, void **ctxp)
+{
+	uint16_t *ctx = malloc(sizeof(uint16_t));
+	*ctx = 0;
+	*ctxp = ctx;
+	return 0;
+}
+
+static int hash_update_crc16_ccitt(struct hash_algo *algo, void *ctx,
+				   const void *buf, unsigned int size,
+				   int is_last)
+{
+	*((uint16_t *)ctx) = crc16_ccitt(*((uint16_t *)ctx), buf, size);
+	return 0;
+}
+
+static int hash_finish_crc16_ccitt(struct hash_algo *algo, void *ctx,
+				   void *dest_buf, int size)
+{
+	if (size < algo->digest_size)
+		return -1;
+
+	*((uint16_t *)dest_buf) = *((uint16_t *)ctx);
+	free(ctx);
+	return 0;
+}
+
 static int hash_init_crc32(struct hash_algo *algo, void **ctxp)
 {
 	uint32_t *ctx = malloc(sizeof(uint32_t));
@@ -160,6 +187,15 @@ static struct hash_algo hash_algo[] = {
 	},
 #endif
 	{
+		.name		= "crc16-ccitt",
+		.digest_size	= 2,
+		.chunk_size	= CHUNKSZ,
+		.hash_func_ws	= crc16_ccitt_wd_buf,
+		.hash_init	= hash_init_crc16_ccitt,
+		.hash_update	= hash_update_crc16_ccitt,
+		.hash_finish	= hash_finish_crc16_ccitt,
+	},
+	{
 		.name		= "crc32",
 		.digest_size	= 4,
 		.chunk_size	= CHUNKSZ_CRC32,
diff --git a/include/u-boot/crc.h b/include/u-boot/crc.h
index 111b22c..788ef29 100644
--- a/include/u-boot/crc.h
+++ b/include/u-boot/crc.h
@@ -13,6 +13,17 @@ unsigned int crc8(unsigned int crc_start, const unsigned char *vptr, int len);
 
 /* lib/crc16.c - 16 bit CRC with polynomial x^16+x^12+x^5+1 (CRC-CCITT) */
 uint16_t crc16_ccitt(uint16_t crc_start, const unsigned char *s, int len);
+/**
+ * crc16_ccitt_wd_buf - Perform CRC16-CCIT on an input buffer and return the
+ *                      16-bit result (network byte-order) in an output buffer
+ *
+ * @in:	input buffer
+ * @len: input buffer length
+ * @out: output buffer (at least 2 bytes)
+ * @chunk_sz: ignored
+ */
+void crc16_ccitt_wd_buf(const uint8_t *in, uint len,
+			uint8_t *out, uint chunk_sz);
 
 /* lib/crc32.c */
 uint32_t crc32 (uint32_t, const unsigned char *, uint);
diff --git a/lib/crc16.c b/lib/crc16.c
index 25bdfd8..f46ba72 100644
--- a/lib/crc16.c
+++ b/lib/crc16.c
@@ -22,6 +22,11 @@
  *==========================================================================
  */
 
+#ifdef USE_HOSTCC
+#include <arpa/inet.h>
+#else
+#include <common.h>
+#endif
 #include <u-boot/crc.h>
 
 /* Table of CRC constants - implements x^16+x^12+x^5+1 */
@@ -60,14 +65,20 @@ static const uint16_t crc16_tab[] = {
 	0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0,
 };
 
-uint16_t crc16_ccitt(uint16_t crc_start, unsigned char *buf, int len)
+uint16_t crc16_ccitt(uint16_t cksum, const unsigned char *buf, int len)
 {
-	int i;
-	uint16_t cksum;
-
-	cksum = crc_start;
-	for (i = 0;  i < len;  i++)
+	for (int i = 0;  i < len;  i++)
 		cksum = crc16_tab[((cksum>>8) ^ *buf++) & 0xff] ^ (cksum << 8);
 
 	return cksum;
 }
+
+void crc16_ccitt_wd_buf(const uint8_t *in, uint len,
+			uint8_t *out, uint chunk_sz)
+{
+	uint16_t crc;
+
+	crc = crc16_ccitt(0, in, len);
+	crc = htons(crc);
+	memcpy(out, &crc, sizeof(crc));
+}
diff --git a/tools/Makefile b/tools/Makefile
index 3c0521f..a338705 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -106,6 +106,7 @@ dumpimage-mkimage-objs := aisimage.o \
 			stm32image.o \
 			$(ROCKCHIP_OBS) \
 			socfpgaimage.o \
+			lib/crc16.o \
 			lib/sha1.o \
 			lib/sha256.o \
 			common/hash.o \
-- 
2.1.4