[PATCH v5] crc-itu-t: Fix typo in CRC ITU-T polynom comment

[PATCH v5] crc-itu-t: Fix typo in CRC ITU-T polynom comment

[Roger Knecht]

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

Re: [PATCH v5] crc-itu-t: Fix typo in CRC ITU-T polynom comment

[Randy Dunlap]

Hi Roger,

On 5/21/22 05:47, Roger Knecht wrote:
> 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>

I don't know which maintainer will merge this since no one is Cc:ed on it.
You will probably need to choose some maintainer to send the patch to.

But let's add the people who merged the header file in the first place
for their comments/review. (done)

> ---
> 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,

-- 
~Randy

Re: [PATCH v5] crc-itu-t: Fix typo in CRC ITU-T polynom comment

[Roger Knecht]

On Sat, May 21, 2022 at 5:44 PM Randy Dunlap <rdunlap@infradead.org> wrote:
> I don't know which maintainer will merge this since no one is Cc:ed on it.
> You will probably need to choose some maintainer to send the patch to.
>
> But let's add the people who merged the header file in the first place
> for their comments/review. (done)

Thanks Randy.

The CRC implementation seems to be unmaintained (no entry in the
MAINTAINER file).
Any idea which maintainer I can send the patch to?

The kernel doc mentions Andrew Morton as last resort (added to CC):
> You should always copy the appropriate subsystem maintainer(s) on any patch to
> code that they maintain; look through the MAINTAINERS file and the source code
> revision history to see who those maintainers are. The script scripts/get_maintainer.pl
> can be very useful at this step. If you cannot find a maintainer for the subsystem you
> are working on, Andrew Morton (akpm@linux-foundation.org) serves as a maintainer
> of last resort.
source: https://www.kernel.org/doc/html/latest/process/submitting-patches.html

Roger

Re: [PATCH v5] crc-itu-t: Fix typo in CRC ITU-T polynom comment

[Randy Dunlap]

On 6/2/22 07:24, Roger Knecht wrote:
> On Sat, May 21, 2022 at 5:44 PM Randy Dunlap <rdunlap@infradead.org> wrote:
>> I don't know which maintainer will merge this since no one is Cc:ed on it.
>> You will probably need to choose some maintainer to send the patch to.
>>
>> But let's add the people who merged the header file in the first place
>> for their comments/review. (done)
> 
> Thanks Randy.
> 
> The CRC implementation seems to be unmaintained (no entry in the
> MAINTAINER file).
> Any idea which maintainer I can send the patch to?

Yes, the 2 people who signed off on its merger are not active AFAICT.

> The kernel doc mentions Andrew Morton as last resort (added to CC):
>> You should always copy the appropriate subsystem maintainer(s) on any patch to
>> code that they maintain; look through the MAINTAINERS file and the source code
>> revision history to see who those maintainers are. The script scripts/get_maintainer.pl
>> can be very useful at this step. If you cannot find a maintainer for the subsystem you
>> are working on, Andrew Morton (akpm@linux-foundation.org) serves as a maintainer
>> of last resort.
> source: https://www.kernel.org/doc/html/latest/process/submitting-patches.html

Yes, Andrew can merge it.
Or possibly Jason (also Cc-ed).

thanks.

-- 
~Randy

Re: [PATCH v5] crc-itu-t: Fix typo in CRC ITU-T polynom comment

[Jason A. Donenfeld]

Hi Randy,

On Thu, Jun 02, 2022 at 09:31:24AM -0700, Randy Dunlap wrote:
> 
> 
> On 6/2/22 07:24, Roger Knecht wrote:
> > On Sat, May 21, 2022 at 5:44 PM Randy Dunlap <rdunlap@infradead.org> wrote:
> >> I don't know which maintainer will merge this since no one is Cc:ed on it.
> >> You will probably need to choose some maintainer to send the patch to.
> >>
> >> But let's add the people who merged the header file in the first place
> >> for their comments/review. (done)
> > 
> > Thanks Randy.
> > 
> > The CRC implementation seems to be unmaintained (no entry in the
> > MAINTAINER file).
> > Any idea which maintainer I can send the patch to?
> 
> Yes, the 2 people who signed off on its merger are not active AFAICT.
> 
> > The kernel doc mentions Andrew Morton as last resort (added to CC):
> >> You should always copy the appropriate subsystem maintainer(s) on any patch to
> >> code that they maintain; look through the MAINTAINERS file and the source code
> >> revision history to see who those maintainers are. The script scripts/get_maintainer.pl
> >> can be very useful at this step. If you cannot find a maintainer for the subsystem you
> >> are working on, Andrew Morton (akpm@linux-foundation.org) serves as a maintainer
> >> of last resort.
> > source: https://www.kernel.org/doc/html/latest/process/submitting-patches.html
> 
> Yes, Andrew can merge it.
> Or possibly Jason (also Cc-ed).

Sure, I can take this.

Jason

> 
> thanks.
> 
> -- 
> ~Randy

Re: [PATCH v5] crc-itu-t: Fix typo in CRC ITU-T polynom comment

[Roger Knecht]

On Thu, Jun 2, 2022 at 7:17 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> On Thu, Jun 02, 2022 at 09:31:24AM -0700, Randy Dunlap wrote:
> > Yes, Andrew can merge it.
> > Or possibly Jason (also Cc-ed).
>
> Sure, I can take this.
>
> Jason

Great, thanks Jason