lkml.org 
[lkml]   [2022]   [May]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v5] crc-itu-t: Fix typo in CRC ITU-T polynom comment
Date
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@norberthealth.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
---
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
\
 
 \ /
  Last update: 2022-05-21 14:48    [W:0.069 / U:1.344 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site