Return-path: Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:32950 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752038AbaEKI2U (ORCPT ); Sun, 11 May 2014 04:28:20 -0400 Date: Sun, 11 May 2014 10:28:11 +0200 From: Pavel Machek To: George Spelvin Cc: jan.nikitenko@gmail.com, linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org, linville@tuxdriver.com, arik@wizery.com, coelho@ti.com, david.gnedt@davizone.at, eliad@wizery.com, laurent.pinchart+renesas@ideasonboard.com, luca@coelho.fi, tony@atomide.com Subject: Re: [PATCH] lib/crc7: Shift crc7() output left 1 bit Message-ID: <20140511082811.GA2695@xo-6d-61-c0.localdomain> (sfid-20140511_102841_528968_1BBB0572) References: <20140511043526.18113.qmail@ns.horizon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20140511043526.18113.qmail@ns.horizon.com> Sender: linux-wireless-owner@vger.kernel.org List-ID: On Sun 2014-05-11 00:35:26, George Spelvin wrote: > This eliminates a 1-bit left shift in every single caller, > and also makes the inner loop of the CRC computation more efficient. > > And purged #include from files that don't use it at all. Looks good, but should not function name change when functionality got completely different? Pavel > > Signed-off-by: George Spelvin > --- > Since all of the affected drivers are officially orphaned, this is > being sent to a hodge-podge of people who touched the files recently. > Assuming the MMC people don't complain, is it okay to send this through > the wireless tree? > > 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 | 2 +- > lib/crc7.c | 74 ++++++++++++++++++++---------------- > 7 files changed, 45 insertions(+), 41 deletions(-) > > diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c > index 0a87e56913..2c9e879c09 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(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 5a4ec56c83..5695628757 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 bf1fa18b97..ede31f048e 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 b06d36d993..47875fc6be 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(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 dbe826dd7c..8b3e38e453 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(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 1786e772d5..d2155dc953 100644 > --- a/include/linux/crc7.h > +++ b/include/linux/crc7.h > @@ -6,7 +6,7 @@ extern const u8 crc7_syndrome_table[256]; > > static inline u8 crc7_byte(u8 crc, u8 data) > { > - return crc7_syndrome_table[(crc << 1) ^ data]; > + return crc7_syndrome_table[crc ^ data]; > } > > extern u8 crc7(u8 crc, const u8 *buffer, size_t len); > diff --git a/lib/crc7.c b/lib/crc7.c > index f1c3a144ce..4a73b26e7a 100644 > --- a/lib/crc7.c > +++ b/lib/crc7.c > @@ -10,40 +10,45 @@ > #include > > > -/* Table for CRC-7 (polynomial x^7 + x^3 + 1) */ > +/* > + * 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_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 > + 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); > > @@ -55,6 +60,9 @@ 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) > { > -- > 1.9.2 -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html