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[18/20] tty: n_gsm: fix implicit CR bit encoding in address field

Message ID 20220414094225.4527-18-daniel.starke@siemens.com
State New
Headers show
Series [01/20] tty: n_gsm: fix missing mux reset on config change at responder | expand

Commit Message

D. Starke April 14, 2022, 9:42 a.m. UTC 
From: Daniel Starke <daniel.starke@siemens.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 5.2.1.2 describes the encoding of the
address field within the frame header. It is made up of the DLCI address,
command/response (CR) bit and EA bit.
Use the predefined CR value instead of a plain 2 in alignment to the
remaining code and to make the encoding obvious.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Greg KH April 15, 2022, 6:33 a.m. UTC | #1 
On Thu, Apr 14, 2022 at 02:42:23AM -0700, D. Starke wrote:
> From: Daniel Starke <daniel.starke@siemens.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 5.2.1.2 describes the encoding of the
> address field within the frame header. It is made up of the DLCI address,
> command/response (CR) bit and EA bit.
> Use the predefined CR value instead of a plain 2 in alignment to the
> remaining code and to make the encoding obvious.
> 
> Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
> Cc: stable@vger.kernel.org

This does not change any functionality, so how is this a "fix" or
relevant for stable backporting?


> Signed-off-by: Daniel Starke <daniel.starke@siemens.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 1e135a71860f..ecd2ecc61b14 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -754,7 +754,7 @@ static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
>  
>  	*--dp = msg->ctrl;
>  	if (gsm->initiator)
> -		*--dp = (msg->addr << 2) | 2 | EA;
> +		*--dp = (msg->addr << 2) | CR | EA;

This is a nice cleanup only.

thanks,

greg k-h
diff mbox series

Patch

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 1e135a71860f..ecd2ecc61b14 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -754,7 +754,7 @@  static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
 
 	*--dp = msg->ctrl;
 	if (gsm->initiator)
-		*--dp = (msg->addr << 2) | 2 | EA;
+		*--dp = (msg->addr << 2) | CR | EA;
 	else
 		*--dp = (msg->addr << 2) | EA;
 	*fcs = gsm_fcs_add_block(INIT_FCS, dp , msg->data - dp);