| Message ID | 1243868091-5315-2-git-send-email-dbaryshkov@gmail.com |
|---|---|
| State | RFC, archived |
| Delegated to: | David Miller |
| Headers | show |
On Mon, 1 Jun 2009 18:54:42 +0400 Dmitry Eremin-Solenikov <dbaryshkov@gmail.com> wrote: > From: Darren Salt <linux@youmustbejoking.demon.co.uk> > > .. > > static inline u16 crc_itu_t_byte(u16 crc, const u8 data) > { > return (crc << 8) ^ crc_itu_t_table[((crc >> 8) ^ data) & 0xff]; > } > > +static inline u16 crc_itu_t_bitreversed_byte(u16 crc, const u8 data) > +{ > + return (crc << 8) ^ crc_itu_t_table[((crc >> 8) ^ bitrev8(data)) & 0xff]; > +} I suspect that inlining these was a mistake, but one which we make often. > #endif /* CRC_ITU_T_H */ > > diff --git a/lib/crc-itu-t.c b/lib/crc-itu-t.c > index a63472b..5562fdd 100644 > --- a/lib/crc-itu-t.c > +++ b/lib/crc-itu-t.c > @@ -64,6 +64,24 @@ u16 crc_itu_t(u16 crc, const u8 *buffer, size_t len) > } > EXPORT_SYMBOL(crc_itu_t); > > +/** > + * crc_itu_t_bitreversed - Compute the CRC-ITU-T for the data buffer; > + * the buffer content is assumed to be bit-reversed kerneldoc doesn't support the breaking of this information across multiple lines. It'll need to be done as a single 120-column line. > + * @crc: previous CRC value > + * @buffer: data pointer > + * @len: number of bytes in the buffer > + * > + * Returns the updated CRC value > + */ > +u16 crc_itu_t_bitreversed(u16 crc, const u8 *buffer, size_t len) > +{ > + while (len--) > + crc = crc_itu_t_bitreversed_byte(crc, *buffer++); > + return crc; > +} > +EXPORT_SYMBOL(crc_itu_t_bitreversed); -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/crc-itu-t.h b/include/linux/crc-itu-t.h index 84920f3..7b2b7ba 100644 --- a/include/linux/crc-itu-t.h +++ b/include/linux/crc-itu-t.h @@ -6,6 +6,9 @@ * Poly 0x0x1021 (x^16 + x^12 + x^15 + 1) * Init 0 * + * The bit-reversed buffer variants may be non-standard, but some firmware + * loaders require them. + * * This source code is licensed under the GNU General Public License, * Version 2. See the file COPYING for more details. */ @@ -14,15 +17,22 @@ #define CRC_ITU_T_H #include <linux/types.h> +#include <linux/bitrev.h> extern u16 const crc_itu_t_table[256]; extern u16 crc_itu_t(u16 crc, const u8 *buffer, size_t len); +extern u16 crc_itu_t_bitreversed(u16 crc, const u8 *buffer, size_t len); static inline u16 crc_itu_t_byte(u16 crc, const u8 data) { return (crc << 8) ^ crc_itu_t_table[((crc >> 8) ^ data) & 0xff]; } +static inline u16 crc_itu_t_bitreversed_byte(u16 crc, const u8 data) +{ + return (crc << 8) ^ crc_itu_t_table[((crc >> 8) ^ bitrev8(data)) & 0xff]; +} + #endif /* CRC_ITU_T_H */ diff --git a/lib/crc-itu-t.c b/lib/crc-itu-t.c index a63472b..5562fdd 100644 --- a/lib/crc-itu-t.c +++ b/lib/crc-itu-t.c @@ -64,6 +64,24 @@ u16 crc_itu_t(u16 crc, const u8 *buffer, size_t len) } EXPORT_SYMBOL(crc_itu_t); +/** + * crc_itu_t_bitreversed - Compute the CRC-ITU-T for the data buffer; + * the buffer content is assumed to be bit-reversed + * + * @crc: previous CRC value + * @buffer: data pointer + * @len: number of bytes in the buffer + * + * Returns the updated CRC value + */ +u16 crc_itu_t_bitreversed(u16 crc, const u8 *buffer, size_t len) +{ + while (len--) + crc = crc_itu_t_bitreversed_byte(crc, *buffer++); + return crc; +} +EXPORT_SYMBOL(crc_itu_t_bitreversed); + MODULE_DESCRIPTION("CRC ITU-T V.41 calculations"); MODULE_LICENSE("GPL");