linux-kernel - [PATCH 2/8] tty: n_gsm: fix C/R bit when sending as a responder

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Message-Id: <1456090717-19913-3-git-send-email-ak77@tnode.com>
Date:	Sun, 21 Feb 2016 22:38:31 +0100
From:	Andrej Krpic <ak77@...de.com>
To:	linux-kernel@...r.kernel.org
Cc:	jslaby@...e.com, gregkh@...uxfoundation.org,
	Andrej Krpic <ak77@...de.com>
Subject: [PATCH 2/8] tty: n_gsm: fix C/R bit when sending as a responder

According to the specification (3GPP TS 27.010 v12.0.0 R1, 5.2.1.2),
C/R bit must be the same for corresponding command and response.
If mux is an initiator (station that initiates DLC 0), valid sent
commands and received responses must have C/R bit set to 1.
For a station that is a responder, valid sent commands and received
responses must have C/R bit set to 0.

Change the value of C/R bit in command and response frames to
depend on whether the station is initator or not.

Signed-off-by: Andrej Krpic <ak77@...de.com>
---
 drivers/tty/n_gsm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index cc3b374..a0fb92c 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -622,7 +622,7 @@ static void gsm_send(struct gsm_mux *gsm, int addr, int cr, int control)
 
 static inline void gsm_response(struct gsm_mux *gsm, int addr, int control)
 {
-	gsm_send(gsm, addr, 0, control);
+	gsm_send(gsm, addr, gsm->initiator ? 0 : 1, control);
 }
 
 /**
@@ -636,7 +636,7 @@ static inline void gsm_response(struct gsm_mux *gsm, int addr, int control)
 
 static inline void gsm_command(struct gsm_mux *gsm, int addr, int control)
 {
-	gsm_send(gsm, addr, 1, control);
+	gsm_send(gsm, addr, gsm->initiator ? 1 : 0, control);
 }
 
 /* Data transmission */
-- 
2.7.0