linux-kernel - [PATCH v3 1/6] tty: n_gsm: add enumeration for gsm encodings

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Date:   Wed, 31 Aug 2022 09:37:55 +0200
From:   "D. Starke" <daniel.starke@...mens.com>
To:     linux-serial@...r.kernel.org, gregkh@...uxfoundation.org,
        jirislaby@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        Daniel Starke <daniel.starke@...mens.com>
Subject: [PATCH v3 1/6] tty: n_gsm: add enumeration for gsm encodings

From: Daniel Starke <daniel.starke@...mens.com>

Add an enumeration for the gsm mux encoding types to improve code
readability and to avoid invalid values. Only two values are defined by the
standard:
- basic option mode
- advanced option mode (uses ISO HDLC standard transparency mechanism)

Signed-off-by: Daniel Starke <daniel.starke@...mens.com>
---
 drivers/tty/n_gsm.c | 30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

Incorporated review comments from Jiri Slaby since v2:
- removed exlicit cast from enum to int
- removed unrelated removal of redundant assignment of gsm->encoding in
  gsmld_open()

Link: https://lore.kernel.org/all/3801995e-1eb5-1184-a9ba-2cec1d19bc58@kernel.org/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index caa5c14ed57f..3fa859a29317 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -184,6 +184,11 @@ struct gsm_control {
 	int error;	/* Error if any */
 };
 
+enum gsm_encoding {
+	GSM_BASIC_OPT,
+	GSM_ADV_OPT,
+};
+
 enum gsm_mux_state {
 	GSM_SEARCH,
 	GSM_START,
@@ -230,7 +235,7 @@ struct gsm_mux {
 	unsigned int address;
 	unsigned int count;
 	bool escape;
-	int encoding;
+	enum gsm_encoding encoding;
 	u8 control;
 	u8 fcs;
 	u8 *txframe;			/* TX framing buffer */
@@ -694,7 +699,7 @@ static int gsm_send(struct gsm_mux *gsm, int addr, int cr, int control)
 	*dp++ = (addr << 2) | (ocr << 1) | EA;
 	*dp++ = control;
 
-	if (gsm->encoding == 0)
+	if (gsm->encoding == GSM_BASIC_OPT)
 		*dp++ = EA; /* Length of data = 0 */
 
 	*dp = 0xFF - gsm_fcs_add_block(INIT_FCS, msg->data, dp - msg->data);
@@ -813,7 +818,7 @@ static int gsm_send_packet(struct gsm_mux *gsm, struct gsm_msg *msg)
 	int len, ret;
 
 
-	if (gsm->encoding == 0) {
+	if (gsm->encoding == GSM_BASIC_OPT) {
 		gsm->txframe[0] = GSM0_SOF;
 		memcpy(gsm->txframe + 1, msg->data, msg->len);
 		gsm->txframe[msg->len + 1] = GSM0_SOF;
@@ -965,7 +970,7 @@ static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
 	u8 *fcs = dp + msg->len;
 
 	/* Fill in the header */
-	if (gsm->encoding == 0) {
+	if (gsm->encoding == GSM_BASIC_OPT) {
 		if (msg->len < 128)
 			*--dp = (msg->len << 1) | EA;
 		else {
@@ -2508,7 +2513,7 @@ static int gsm_activate_mux(struct gsm_mux *gsm)
 	spin_lock_init(&gsm->control_lock);
 	spin_lock_init(&gsm->tx_lock);
 
-	if (gsm->encoding == 0)
+	if (gsm->encoding == GSM_BASIC_OPT)
 		gsm->receive = gsm0_receive;
 	else
 		gsm->receive = gsm1_receive;
@@ -2618,7 +2623,7 @@ static struct gsm_mux *gsm_alloc_mux(void)
 	gsm->n2 = N2;
 	gsm->ftype = UIH;
 	gsm->adaption = 1;
-	gsm->encoding = 1;
+	gsm->encoding = GSM_ADV_OPT;
 	gsm->mru = 64;	/* Default to encoding 1 so these should be 64 */
 	gsm->mtu = 64;
 	gsm->dead = true;	/* Avoid early tty opens */
@@ -2719,7 +2724,7 @@ static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
 	gsm->initiator = c->initiator;
 	gsm->mru = c->mru;
 	gsm->mtu = c->mtu;
-	gsm->encoding = c->encapsulation;
+	gsm->encoding = c->encapsulation ? GSM_ADV_OPT : GSM_BASIC_OPT;
 	gsm->adaption = c->adaption;
 	gsm->n2 = c->n2;
 
@@ -2942,8 +2947,7 @@ static int gsmld_open(struct tty_struct *tty)
 	tty->receive_room = 65536;
 
 	/* Attach the initial passive connection */
-	gsm->encoding = 1;
-
+	gsm->encoding = GSM_ADV_OPT;
 	gsmld_attach_gsm(tty, gsm);
 
 	timer_setup(&gsm->kick_timer, gsm_kick_timer, 0);
@@ -3345,7 +3349,7 @@ static int gsm_modem_upd_via_msc(struct gsm_dlci *dlci, u8 brk)
 	struct gsm_control *ctrl;
 	int len = 2;
 
-	if (dlci->gsm->encoding != 0)
+	if (dlci->gsm->encoding != GSM_BASIC_OPT)
 		return 0;
 
 	modembits[0] = (dlci->addr << 2) | 2 | EA;  /* DLCI, Valid, EA */
@@ -3374,7 +3378,7 @@ static int gsm_modem_update(struct gsm_dlci *dlci, u8 brk)
 		/* Send convergence layer type 2 empty data frame. */
 		gsm_modem_upd_via_data(dlci, brk);
 		return 0;
-	} else if (dlci->gsm->encoding == 0) {
+	} else if (dlci->gsm->encoding == GSM_BASIC_OPT) {
 		/* Send as MSC control message. */
 		return gsm_modem_upd_via_msc(dlci, brk);
 	}
@@ -3398,8 +3402,8 @@ static int gsm_carrier_raised(struct tty_port *port)
 	 * Basic mode with control channel in ADM mode may not respond
 	 * to CMD_MSC at all and modem_rx is empty.
 	 */
-	if (gsm->encoding == 0 && gsm->dlci[0]->mode == DLCI_MODE_ADM &&
-	    !dlci->modem_rx)
+	if (gsm->encoding == GSM_BASIC_OPT &&
+	    gsm->dlci[0]->mode == DLCI_MODE_ADM && !dlci->modem_rx)
 		return 1;
 
 	return dlci->modem_rx & TIOCM_CD;
-- 
2.34.1