The code comment says that the polynom is x^16 + x^12 + x^15 + 1, but the correct polynom is x^16 + x^12 + x^5 + 1. Quote from page 2 in the ITU-T V.41 specification: "2 Encoding and checking process The service bits and information bits, taken in conjunction, correspond to the coefficients of a message polynomial having terms from x^(n-1) (n = total number of bits in a block or sequence) down to x^16. This polynomial is divided, modulo 2, by the generating polynomial x^16 + x^12 + x^5 + 1. [...]" Source: https://www.itu.int/rec/T-REC-V.41-198811-I/en) The hex polynom 0x1021 and CRC code implementation are correct. Signed-off-by: Roger Knecht <roger@xxxxxxxxxxxxxxxxx> Acked-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> --- Changes: v5: Clean up patch description and added acked-by v4: Changed comment from /** to /* (the comment is not a kernel doc comment) v3: Moved "changes and thanks" out of the commit message. v2: Extended patch description include/linux/crc-itu-t.h | 2 +- lib/crc-itu-t.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/crc-itu-t.h b/include/linux/crc-itu-t.h index a4367051e192..2f991a427ade 100644 --- a/include/linux/crc-itu-t.h +++ b/include/linux/crc-itu-t.h @@ -4,7 +4,7 @@ * * Implements the standard CRC ITU-T V.41: * Width 16 - * Poly 0x1021 (x^16 + x^12 + x^15 + 1) + * Poly 0x1021 (x^16 + x^12 + x^5 + 1) * Init 0 */ diff --git a/lib/crc-itu-t.c b/lib/crc-itu-t.c index 1974b355c148..1d26a1647da5 100644 --- a/lib/crc-itu-t.c +++ b/lib/crc-itu-t.c @@ -7,7 +7,7 @@ #include <linux/module.h> #include <linux/crc-itu-t.h> -/** CRC table for the CRC ITU-T V.41 0x1021 (x^16 + x^12 + x^15 + 1) */ +/* CRC table for the CRC ITU-T V.41 0x1021 (x^16 + x^12 + x^5 + 1) */ const u16 crc_itu_t_table[256] = { 0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, -- 2.17.1
