[PATCH] crc-itu-t: fix typo in CRC ITU-T polynomial comment

[PATCH] crc-itu-t: fix typo in CRC ITU-T polynomial comment

[Sascha Hauer]

Based on Linux commit 77991645952c2 ("crc-itu-t: fix typo in CRC ITU-T polynomial comment"):

| The code comment says that the polynomial is x^16 + x^12 + x^15 + 1, but
| the correct polynomial is x^16 + x^12 + x^5 + 1. Quoting from page 2 in
| the ITU-T V.41 specification [1]:
|
|   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.
|
| The hex (truncated) polynomial 0x1021 and CRC code implementation are
| correct, however.
|
| [1] https://www.itu.int/rec/T-REC-V.41-198811-I/en
|
| Signed-off-by: Roger Knecht <roger@norberthealth.com>
| Acked-by: Randy Dunlap <rdunlap@infradead.org>
| Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 crypto/crc-itu-t.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crypto/crc-itu-t.c b/crypto/crc-itu-t.c
index 837a6464b6..fcbed706a9 100644
--- a/crypto/crc-itu-t.c
+++ b/crypto/crc-itu-t.c
@@ -12,7 +12,7 @@ static u16 crc_itu_t_table[256];
 /*
  * 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
  */
 static u16 crc_itu_t_byte(u16 crc, const u8 data)
-- 
2.47.3

Re: [PATCH] crc-itu-t: fix typo in CRC ITU-T polynomial comment

[Sascha Hauer]

On Thu, 18 Sep 2025 08:00:52 +0200, Sascha Hauer wrote:
> Based on Linux commit 77991645952c2 ("crc-itu-t: fix typo in CRC ITU-T polynomial comment"):
> 
> | The code comment says that the polynomial is x^16 + x^12 + x^15 + 1, but
> | the correct polynomial is x^16 + x^12 + x^5 + 1. Quoting from page 2 in
> | the ITU-T V.41 specification [1]:
> |
> |   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.
> |
> | The hex (truncated) polynomial 0x1021 and CRC code implementation are
> | correct, however.
> |
> | [1] https://www.itu.int/rec/T-REC-V.41-198811-I/en
> |
> | Signed-off-by: Roger Knecht <roger@norberthealth.com>
> | Acked-by: Randy Dunlap <rdunlap@infradead.org>
> | Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> 
> [...]

Applied, thanks!

[1/1] crc-itu-t: fix typo in CRC ITU-T polynomial comment
      https://git.pengutronix.de/cgit/barebox/commit/?id=f148e3d94a27 (link may not be stable)

Best regards,
-- 
Sascha Hauer <s.hauer@pengutronix.de>