Re: [PATCH 01/10] crc-itu-t: add bit-reversed calculation
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From: Andrew Morton <akpm@linux-foundation.org>
Date: 2009-06-04 00:05:32
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On Mon, 1 Jun 2009 18:54:42 +0400 Dmitry Eremin-Solenikov [off-list ref] wrote:
From: Darren Salt <redacted>
..
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.
quoted hunk ↗ jump to hunk
#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.
quoted hunk ↗ jump to hunk
+ * @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);