lib/crc16.c: Rename cyg_crc16() to crc16_ccitt() and add crc start value

The original name of this function is unclear. This patch renames this
CRC16 function to crc16_ccitt() matching its name with its
implementation.

To make the usage of this function more flexible, lets add the CRC start
value as parameter to this function. This way it can be used by other
functions requiring different start values than 0 as well.

Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Tom Rini <trini@konsulko.com>

common/xyzModem.c

@@ -446,7 +446,7 @@ xyzModem_get_hdr (void)
   /* Verify checksum/CRC */
   if (xyz.crc_mode)
     {
-      cksum = cyg_crc16 (xyz.pkt, xyz.len);
+      cksum = crc16_ccitt(0, xyz.pkt, xyz.len);
       if (cksum != ((xyz.crc1 << 8) | xyz.crc2))
 	{
 	  ZM_DEBUG (zm_dprintf ("CRC error - recvd: %02x%02x, computed: %x\n",

drivers/mmc/mmc_spi.c

@@ -91,7 +91,7 @@ static uint mmc_spi_readdata(struct mmc *mmc, void *xbuf,
 			spi_xfer(spi, bsize * 8, NULL, buf, 0);
 			spi_xfer(spi, 2 * 8, NULL, &crc, 0);
 #ifdef CONFIG_MMC_SPI_CRC_ON
-			if (be_to_cpu16(cyg_crc16(buf, bsize)) != crc) {
+			if (be_to_cpu16(crc16_ccitt(0, buf, bsize)) != crc) {
 				debug("%s: CRC error\n", mmc->cfg->name);
 				r1 = R1_SPI_COM_CRC;
 				break;
@@ -120,7 +120,7 @@ static uint mmc_spi_writedata(struct mmc *mmc, const void *xbuf,
 	tok[1] = multi ? SPI_TOKEN_MULTI_WRITE : SPI_TOKEN_SINGLE;
 	while (bcnt--) {
 #ifdef CONFIG_MMC_SPI_CRC_ON
-		crc = cpu_to_be16(cyg_crc16((u8 *)buf, bsize));
+		crc = cpu_to_be16(crc16_ccitt(0, (u8 *)buf, bsize));
 #endif
 		spi_xfer(spi, 2 * 8, tok, NULL, 0);
 		spi_xfer(spi, bsize * 8, buf, NULL, 0);

include/crc.h

@@ -62,8 +62,8 @@ cyg_ether_crc32(unsigned char *s, int len);
 extern uint32_t
 cyg_ether_crc32_accumulate(uint32_t crc, unsigned char *s, int len);
 
-/* 16 bit CRC with polynomial x^16+x^12+x^5+1 */
+/* 16 bit CRC with polynomial x^16+x^12+x^5+1 (CRC-CCITT) */
 
-extern uint16_t cyg_crc16(unsigned char *s, int len);
+uint16_t crc16_ccitt(uint16_t crc_start, unsigned char *s, int len);
 
 #endif /* _SERVICES_CRC_CRC_H_ */

lib/crc16.c

@@ -61,12 +61,12 @@ static const uint16_t crc16_tab[] = {
 	0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0,
 };
 
-uint16_t cyg_crc16(unsigned char *buf, int len)
+uint16_t crc16_ccitt(uint16_t crc_start, unsigned char *buf, int len)
 {
 	int i;
 	uint16_t cksum;
 
-	cksum = 0;
+	cksum = crc_start;
 	for (i = 0;  i < len;  i++)
 		cksum = crc16_tab[((cksum>>8) ^ *buf++) & 0xff] ^ (cksum << 8);