| Message ID | 1244021629-18409-2-git-send-email-dbaryshkov@gmail.com |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
On Wed, 2009-06-03 at 13:33 +0400, Dmitry Eremin-Solenikov wrote: [...] > +/** > + * crc_itu_t_bitreversed - Compute the CRC-ITU-T for the data buffer; > + * the buffer content is assumed to be bit-reversed [...] This short description spills onto two lines which is invalid and breaks the generation of docs. Sorry to point this out after recommending the patch to you. I've changed the description to "crc_itu_t_bitreversed - Compute the CRC-ITU-T for a bit-reversed data buffer" all on one line. Ben.
2009/6/3 Ben Hutchings <ben@decadent.org.uk>: > On Wed, 2009-06-03 at 13:33 +0400, Dmitry Eremin-Solenikov wrote: > [...] >> +/** >> + * crc_itu_t_bitreversed - Compute the CRC-ITU-T for the data buffer; >> + * the buffer content is assumed to be bit-reversed > [...] > > This short description spills onto two lines which is invalid and breaks > the generation of docs. Sorry to point this out after recommending the > patch to you. > > I've changed the description to "crc_itu_t_bitreversed - Compute the > CRC-ITU-T for a bit-reversed data buffer" all on one line. Changing patch here in accordance with your suggestion.
On Wed, Jun 03, 2009 at 01:43:24PM +0100, Ben Hutchings wrote: > On Wed, 2009-06-03 at 13:33 +0400, Dmitry Eremin-Solenikov wrote: > [...] > > +/** > > + * crc_itu_t_bitreversed - Compute the CRC-ITU-T for the data buffer; > > + * the buffer content is assumed to be bit-reversed > [...] > > This short description spills onto two lines which is invalid and breaks > the generation of docs. Sorry to point this out after recommending the > patch to you. > > I've changed the description to "crc_itu_t_bitreversed - Compute the > CRC-ITU-T for a bit-reversed data buffer" all on one line. Anyway, this patch isn't necessary for the first round of patches, we are submitting now (got in by a mistake).
Hi, On Wed, Jun 03, 2009 at 01:43:24PM +0100, Ben Hutchings wrote: > On Wed, 2009-06-03 at 13:33 +0400, Dmitry Eremin-Solenikov wrote: > [...] > > +/** > > + * crc_itu_t_bitreversed - Compute the CRC-ITU-T for the data buffer; > > + * the buffer content is assumed to be bit-reversed > [...] > > This short description spills onto two lines which is invalid and breaks > the generation of docs. Sorry to point this out after recommending the > patch to you. > > I've changed the description to "crc_itu_t_bitreversed - Compute the > CRC-ITU-T for a bit-reversed data buffer" all on one line. Just another not w.r.t. this patch: one should add 'select BITREVERSE' to this Kconfig entry, as it depends on bitreversing stuff.
[non-HTML reply, sorry about that] On Sunday 21 June 2009, Dmitry Eremin-Solenikov wrote: > Hi, > > > On Wed, Jun 03, 2009 at 01:43:24PM +0100, Ben Hutchings wrote: > > On Wed, 2009-06-03 at 13:33 +0400, Dmitry Eremin-Solenikov wrote: > > [...] > > > +/** > > > + * crc_itu_t_bitreversed - Compute the CRC-ITU-T for the data buffer; > > > + * the buffer content is assumed to be bit-reversed > > [...] > > > > This short description spills onto two lines which is invalid and breaks > > the generation of docs. Sorry to point this out after recommending the > > patch to you. > > > > I've changed the description to "crc_itu_t_bitreversed - Compute the > > CRC-ITU-T for a bit-reversed data buffer" all on one line. > > Just another not w.r.t. this patch: one should add 'select BITREVERSE' > to this Kconfig entry, as it depends on bitreversing stuff. What also might be interesting, have you checked the crc-ccitt algorithm? I had come across a crc_itu_t with bitreverse implementation in the past as well, and I could simplify the implementation by using crc-ccit and only call bitreverse on the last output. So something like: u16 crc = crc_ccitt(~0, data, len); u16 crc_itu_t = swab16(crc); Instead of bitreverse for every step, only a single byteswap was needed. You need to check if this indeed works for your driver, but this would reduce the number of times bitrev is called, and also prevents the BITREV dependency for the crc implementation. Ivo -- 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");