linux-kernel - Re: [PATCH 1/1] tty: n_gsm: fix encoding of control signal octet bit DV

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Date:   Thu, 17 Feb 2022 10:56:42 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     daniel.starke@...mens.com
Cc:     linux-serial@...r.kernel.org, jirislaby@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] tty: n_gsm: fix encoding of control signal octet bit
 DV

On Thu, Feb 17, 2022 at 12:05:49AM -0800, daniel.starke@...mens.com wrote:
> 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 5.4.6.3.7 describes the encoding of the
> control signal octet used by the MSC (modem status command). The same
> encoding is also used in convergence layer type 2 as described in chapter
> 5.5.2. Table 7 and 24 both require the DV (data valid) bit to be set 1 for
> outgoing control signal octets sent by the DTE (data terminal equipment),
> i.e. for the initiator side.
> Currently, the DV bit is only set if CD (carrier detect) is on, regardless
> of the side.
> 
> This patch fixes this behavior by setting the DV bit on the initiator side
> unconditionally.
> 
> Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
> Cc: stable@...r.kernel.org
> Signed-off-by: Daniel Starke <daniel.starke@...mens.com>
> ---
>  drivers/tty/n_gsm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 0b1808e3a912..e199315a158e 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -439,7 +439,7 @@ static u8 gsm_encode_modem(const struct gsm_dlci *dlci)
>  		modembits |= MDM_RTR;
>  	if (dlci->modem_tx & TIOCM_RI)
>  		modembits |= MDM_IC;
> -	if (dlci->modem_tx & TIOCM_CD)
> +	if (dlci->modem_tx & TIOCM_CD || dlci->gsm->initiator)
>  		modembits |= MDM_DV;
>  	return modembits;
>  }
> -- 
> 2.25.1
> 

All of these are patch 1/1, which is odd :(

Please renumber them properly and resend.

thanks,

greg k-h