From 1836eea209546b870dd83f3f4ef234d6598a560d Mon Sep 17 00:00:00 2001 From: George Spelvin Date: Sat, 10 May 2014 10:32:57 -0400 Subject: [PATCH] lib/crc7: Shift crc7() output left 1 bit This eliminates a 1-bit left shift in every single caller, and makes the inner loop of the CRC computation more efficient. Renamed crc7 to crc7_be (big-endian) since the interface changed. Also purged #include from files that don't use it at all. Signed-off-by: George Spelvin Reviewed-by: Pavel Machek Acked-by: Ulf Hansson Signed-off-by: John W. Linville --- drivers/mmc/host/mmc_spi.c | 2 +- drivers/net/wireless/ti/wl1251/acx.c | 1 - drivers/net/wireless/ti/wl1251/cmd.c | 1 - drivers/net/wireless/ti/wl1251/spi.c | 3 +- drivers/net/wireless/ti/wlcore/spi.c | 3 +- include/linux/crc7.h | 8 +-- lib/crc7.c | 84 +++++++++++++++------------- 7 files changed, 53 insertions(+), 49 deletions(-) diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c index 0a87e5691341..338e2202eaaa 100644 --- a/drivers/mmc/host/mmc_spi.c +++ b/drivers/mmc/host/mmc_spi.c @@ -472,7 +472,7 @@ mmc_spi_command_send(struct mmc_spi_host *host, *cp++ = (u8)(arg >> 16); *cp++ = (u8)(arg >> 8); *cp++ = (u8)arg; - *cp++ = (crc7(0, &data->status[1], 5) << 1) | 0x01; + *cp++ = crc7_be(0, &data->status[1], 5) | 0x01; /* Then, read up to 13 bytes (while writing all-ones): * - N(CR) (== 1..8) bytes of all-ones diff --git a/drivers/net/wireless/ti/wl1251/acx.c b/drivers/net/wireless/ti/wl1251/acx.c index 5a4ec56c83d0..5695628757ee 100644 --- a/drivers/net/wireless/ti/wl1251/acx.c +++ b/drivers/net/wireless/ti/wl1251/acx.c @@ -2,7 +2,6 @@ #include #include -#include #include "wl1251.h" #include "reg.h" diff --git a/drivers/net/wireless/ti/wl1251/cmd.c b/drivers/net/wireless/ti/wl1251/cmd.c index bf1fa18b9786..ede31f048ef9 100644 --- a/drivers/net/wireless/ti/wl1251/cmd.c +++ b/drivers/net/wireless/ti/wl1251/cmd.c @@ -2,7 +2,6 @@ #include #include -#include #include #include "wl1251.h" diff --git a/drivers/net/wireless/ti/wl1251/spi.c b/drivers/net/wireless/ti/wl1251/spi.c index b06d36d99362..e94b57cd5a22 100644 --- a/drivers/net/wireless/ti/wl1251/spi.c +++ b/drivers/net/wireless/ti/wl1251/spi.c @@ -122,8 +122,7 @@ static void wl1251_spi_wake(struct wl1251 *wl) crc[3] = cmd[6]; crc[4] = cmd[5]; - cmd[4] |= crc7(0, crc, WSPI_INIT_CMD_CRC_LEN) << 1; - cmd[4] |= WSPI_INIT_CMD_END; + cmd[4] = crc7_be(0, crc, WSPI_INIT_CMD_CRC_LEN) | WSPI_INIT_CMD_END; t.tx_buf = cmd; t.len = WSPI_INIT_CMD_LEN; diff --git a/drivers/net/wireless/ti/wlcore/spi.c b/drivers/net/wireless/ti/wlcore/spi.c index 5f3a389dd74c..1d4ddabe6063 100644 --- a/drivers/net/wireless/ti/wlcore/spi.c +++ b/drivers/net/wireless/ti/wlcore/spi.c @@ -151,8 +151,7 @@ static void wl12xx_spi_init(struct device *child) crc[3] = cmd[6]; crc[4] = cmd[5]; - cmd[4] |= crc7(0, crc, WSPI_INIT_CMD_CRC_LEN) << 1; - cmd[4] |= WSPI_INIT_CMD_END; + cmd[4] = crc7_be(0, crc, WSPI_INIT_CMD_CRC_LEN) | WSPI_INIT_CMD_END; t.tx_buf = cmd; t.len = WSPI_INIT_CMD_LEN; diff --git a/include/linux/crc7.h b/include/linux/crc7.h index 1786e772d5c6..d590765106f3 100644 --- a/include/linux/crc7.h +++ b/include/linux/crc7.h @@ -2,13 +2,13 @@ #define _LINUX_CRC7_H #include -extern const u8 crc7_syndrome_table[256]; +extern const u8 crc7_be_syndrome_table[256]; -static inline u8 crc7_byte(u8 crc, u8 data) +static inline u8 crc7_be_byte(u8 crc, u8 data) { - return crc7_syndrome_table[(crc << 1) ^ data]; + return crc7_be_syndrome_table[crc ^ data]; } -extern u8 crc7(u8 crc, const u8 *buffer, size_t len); +extern u8 crc7_be(u8 crc, const u8 *buffer, size_t len); #endif diff --git a/lib/crc7.c b/lib/crc7.c index f1c3a144cec1..bf6255e23919 100644 --- a/lib/crc7.c +++ b/lib/crc7.c @@ -10,42 +10,47 @@ #include -/* Table for CRC-7 (polynomial x^7 + x^3 + 1) */ -const u8 crc7_syndrome_table[256] = { - 0x00, 0x09, 0x12, 0x1b, 0x24, 0x2d, 0x36, 0x3f, - 0x48, 0x41, 0x5a, 0x53, 0x6c, 0x65, 0x7e, 0x77, - 0x19, 0x10, 0x0b, 0x02, 0x3d, 0x34, 0x2f, 0x26, - 0x51, 0x58, 0x43, 0x4a, 0x75, 0x7c, 0x67, 0x6e, - 0x32, 0x3b, 0x20, 0x29, 0x16, 0x1f, 0x04, 0x0d, - 0x7a, 0x73, 0x68, 0x61, 0x5e, 0x57, 0x4c, 0x45, - 0x2b, 0x22, 0x39, 0x30, 0x0f, 0x06, 0x1d, 0x14, - 0x63, 0x6a, 0x71, 0x78, 0x47, 0x4e, 0x55, 0x5c, - 0x64, 0x6d, 0x76, 0x7f, 0x40, 0x49, 0x52, 0x5b, - 0x2c, 0x25, 0x3e, 0x37, 0x08, 0x01, 0x1a, 0x13, - 0x7d, 0x74, 0x6f, 0x66, 0x59, 0x50, 0x4b, 0x42, - 0x35, 0x3c, 0x27, 0x2e, 0x11, 0x18, 0x03, 0x0a, - 0x56, 0x5f, 0x44, 0x4d, 0x72, 0x7b, 0x60, 0x69, - 0x1e, 0x17, 0x0c, 0x05, 0x3a, 0x33, 0x28, 0x21, - 0x4f, 0x46, 0x5d, 0x54, 0x6b, 0x62, 0x79, 0x70, - 0x07, 0x0e, 0x15, 0x1c, 0x23, 0x2a, 0x31, 0x38, - 0x41, 0x48, 0x53, 0x5a, 0x65, 0x6c, 0x77, 0x7e, - 0x09, 0x00, 0x1b, 0x12, 0x2d, 0x24, 0x3f, 0x36, - 0x58, 0x51, 0x4a, 0x43, 0x7c, 0x75, 0x6e, 0x67, - 0x10, 0x19, 0x02, 0x0b, 0x34, 0x3d, 0x26, 0x2f, - 0x73, 0x7a, 0x61, 0x68, 0x57, 0x5e, 0x45, 0x4c, - 0x3b, 0x32, 0x29, 0x20, 0x1f, 0x16, 0x0d, 0x04, - 0x6a, 0x63, 0x78, 0x71, 0x4e, 0x47, 0x5c, 0x55, - 0x22, 0x2b, 0x30, 0x39, 0x06, 0x0f, 0x14, 0x1d, - 0x25, 0x2c, 0x37, 0x3e, 0x01, 0x08, 0x13, 0x1a, - 0x6d, 0x64, 0x7f, 0x76, 0x49, 0x40, 0x5b, 0x52, - 0x3c, 0x35, 0x2e, 0x27, 0x18, 0x11, 0x0a, 0x03, - 0x74, 0x7d, 0x66, 0x6f, 0x50, 0x59, 0x42, 0x4b, - 0x17, 0x1e, 0x05, 0x0c, 0x33, 0x3a, 0x21, 0x28, - 0x5f, 0x56, 0x4d, 0x44, 0x7b, 0x72, 0x69, 0x60, - 0x0e, 0x07, 0x1c, 0x15, 0x2a, 0x23, 0x38, 0x31, - 0x46, 0x4f, 0x54, 0x5d, 0x62, 0x6b, 0x70, 0x79 +/* + * Table for CRC-7 (polynomial x^7 + x^3 + 1). + * This is a big-endian CRC (msbit is highest power of x), + * aligned so the msbit of the byte is the x^6 coefficient + * and the lsbit is not used. + */ +const u8 crc7_be_syndrome_table[256] = { + 0x00, 0x12, 0x24, 0x36, 0x48, 0x5a, 0x6c, 0x7e, + 0x90, 0x82, 0xb4, 0xa6, 0xd8, 0xca, 0xfc, 0xee, + 0x32, 0x20, 0x16, 0x04, 0x7a, 0x68, 0x5e, 0x4c, + 0xa2, 0xb0, 0x86, 0x94, 0xea, 0xf8, 0xce, 0xdc, + 0x64, 0x76, 0x40, 0x52, 0x2c, 0x3e, 0x08, 0x1a, + 0xf4, 0xe6, 0xd0, 0xc2, 0xbc, 0xae, 0x98, 0x8a, + 0x56, 0x44, 0x72, 0x60, 0x1e, 0x0c, 0x3a, 0x28, + 0xc6, 0xd4, 0xe2, 0xf0, 0x8e, 0x9c, 0xaa, 0xb8, + 0xc8, 0xda, 0xec, 0xfe, 0x80, 0x92, 0xa4, 0xb6, + 0x58, 0x4a, 0x7c, 0x6e, 0x10, 0x02, 0x34, 0x26, + 0xfa, 0xe8, 0xde, 0xcc, 0xb2, 0xa0, 0x96, 0x84, + 0x6a, 0x78, 0x4e, 0x5c, 0x22, 0x30, 0x06, 0x14, + 0xac, 0xbe, 0x88, 0x9a, 0xe4, 0xf6, 0xc0, 0xd2, + 0x3c, 0x2e, 0x18, 0x0a, 0x74, 0x66, 0x50, 0x42, + 0x9e, 0x8c, 0xba, 0xa8, 0xd6, 0xc4, 0xf2, 0xe0, + 0x0e, 0x1c, 0x2a, 0x38, 0x46, 0x54, 0x62, 0x70, + 0x82, 0x90, 0xa6, 0xb4, 0xca, 0xd8, 0xee, 0xfc, + 0x12, 0x00, 0x36, 0x24, 0x5a, 0x48, 0x7e, 0x6c, + 0xb0, 0xa2, 0x94, 0x86, 0xf8, 0xea, 0xdc, 0xce, + 0x20, 0x32, 0x04, 0x16, 0x68, 0x7a, 0x4c, 0x5e, + 0xe6, 0xf4, 0xc2, 0xd0, 0xae, 0xbc, 0x8a, 0x98, + 0x76, 0x64, 0x52, 0x40, 0x3e, 0x2c, 0x1a, 0x08, + 0xd4, 0xc6, 0xf0, 0xe2, 0x9c, 0x8e, 0xb8, 0xaa, + 0x44, 0x56, 0x60, 0x72, 0x0c, 0x1e, 0x28, 0x3a, + 0x4a, 0x58, 0x6e, 0x7c, 0x02, 0x10, 0x26, 0x34, + 0xda, 0xc8, 0xfe, 0xec, 0x92, 0x80, 0xb6, 0xa4, + 0x78, 0x6a, 0x5c, 0x4e, 0x30, 0x22, 0x14, 0x06, + 0xe8, 0xfa, 0xcc, 0xde, 0xa0, 0xb2, 0x84, 0x96, + 0x2e, 0x3c, 0x0a, 0x18, 0x66, 0x74, 0x42, 0x50, + 0xbe, 0xac, 0x9a, 0x88, 0xf6, 0xe4, 0xd2, 0xc0, + 0x1c, 0x0e, 0x38, 0x2a, 0x54, 0x46, 0x70, 0x62, + 0x8c, 0x9e, 0xa8, 0xba, 0xc4, 0xd6, 0xe0, 0xf2 }; -EXPORT_SYMBOL(crc7_syndrome_table); +EXPORT_SYMBOL(crc7_be_syndrome_table); /** * crc7 - update the CRC7 for the data buffer @@ -55,14 +60,17 @@ EXPORT_SYMBOL(crc7_syndrome_table); * Context: any * * Returns the updated CRC7 value. + * The CRC7 is left-aligned in the byte (the lsbit is always 0), as that + * makes the computation easier, and all callers want it in that form. + * */ -u8 crc7(u8 crc, const u8 *buffer, size_t len) +u8 crc7_be(u8 crc, const u8 *buffer, size_t len) { while (len--) - crc = crc7_byte(crc, *buffer++); + crc = crc7_be_byte(crc, *buffer++); return crc; } -EXPORT_SYMBOL(crc7); +EXPORT_SYMBOL(crc7_be); MODULE_DESCRIPTION("CRC7 calculations"); MODULE_LICENSE("GPL"); -- 2.20.1