linux-kernel - Re: [PATCH 16/20] tty: n_gsm: fix invalid command/response bit check for UI/UIH frames

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Date:   Fri, 15 Apr 2022 08:31:23 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     "D. Starke" <daniel.starke@...mens.com>
Cc:     linux-serial@...r.kernel.org, jirislaby@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 16/20] tty: n_gsm: fix invalid command/response bit check
 for UI/UIH frames

On Thu, Apr 14, 2022 at 02:42:21AM -0700, D. Starke wrote:
> From: Daniel Starke <daniel.starke@...mens.com>
> 
> n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010.
> See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516
> The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to
> the newer 27.010 here. Chapter 5.4.3.1 states the CR bit in UI and UIH
> frames shall always be set 1 by the initiator and 0 by the responder.

This has nothing to do with the change you made here.


> Currently, gsm_queue() has a pre-processor gated (excluded) check which
> treats all frames that conform to the standard as malformed frames.
> Remove this optional code to avoid confusion and possible breaking changes
> in case that someone includes it.

Again, nothing to do with the code change.

> 
> Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")

This "fixes" nothing :(

> Cc: stable@...r.kernel.org

How is commenting out unused code a stable backport requirement?

> Signed-off-by: Daniel Starke <daniel.starke@...mens.com>
> ---
>  drivers/tty/n_gsm.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index e9a7d9483c1f..f4ec48c0d6d7 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -1896,10 +1896,6 @@ static void gsm_queue(struct gsm_mux *gsm)
>  	case UI|PF:
>  	case UIH:
>  	case UIH|PF:
> -#if 0
> -		if (cr)
> -			goto invalid;
> -#endif

All you are doing is cleaning up dead code.  Not a big deal, and not
worth all the text above to confuse people :(

thanks,

greg k-h