[PATCH v2 1/6] tty: n_gsm: add enumeration for gsm encodings

[PATCH v2 1/6] tty: n_gsm: add enumeration for gsm encodings

[D. Starke]

From: Daniel Starke <daniel.starke@siemens.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)

Also remove redundant configuration in gsmld_open(). The same value is
already set in gsm_alloc_mux() which is also called in gsmld_open().

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 31 +++++++++++++++++--------------
 1 file changed, 17 insertions(+), 14 deletions(-)

No changes since v1.

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index caa5c14ed57f..5bf09d129357 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 */
@@ -2651,7 +2656,7 @@ static void gsm_copy_config_values(struct gsm_mux *gsm,
 {
 	memset(c, 0, sizeof(*c));
 	c->adaption = gsm->adaption;
-	c->encapsulation = gsm->encoding;
+	c->encapsulation = (int)gsm->encoding;
 	c->initiator = gsm->initiator;
 	c->t1 = gsm->t1;
 	c->t2 = gsm->t2;
@@ -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 +2947,6 @@ static int gsmld_open(struct tty_struct *tty)
 	tty->receive_room = 65536;
 
 	/* Attach the initial passive connection */
-	gsm->encoding = 1;
-
 	gsmld_attach_gsm(tty, gsm);
 
 	timer_setup(&gsm->kick_timer, gsm_kick_timer, 0);
@@ -3345,7 +3348,7 @@ 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 +3377,7 @@ 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 +3401,8 @@ 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

[PATCH v2 2/6] tty: n_gsm: name gsm tty device minors

[D. Starke]

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

Add a macro which defines the possible number of virtual devices for n_gsm
to improve code readability.

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

No changes since v1.

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 5bf09d129357..ed399d57b197 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -164,6 +164,9 @@ struct gsm_dlci {
 	struct net_device *net; /* network interface, if created */
 };
 
+/* Total number of supported devices */
+#define GSM_TTY_MINORS		256
+
 /* DLCI 0, 62/63 are special or reserved see gsmtty_open */
 
 #define NUM_DLCI		64
@@ -3748,7 +3751,7 @@ static int __init gsm_init(void)
 		return status;
 	}
 
-	gsm_tty_driver = tty_alloc_driver(256, TTY_DRIVER_REAL_RAW |
+	gsm_tty_driver = tty_alloc_driver(GSM_TTY_MINORS, TTY_DRIVER_REAL_RAW |
 			TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_HARDWARE_BREAK);
 	if (IS_ERR(gsm_tty_driver)) {
 		pr_err("gsm_init: tty allocation failed.\n");
-- 
2.34.1

[PATCH v2 3/6] tty: n_gsm: replace use of gsm_read_ea() with gsm_read_ea_val()

[D. Starke]

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

Replace the use of gsm_read_ea() with gsm_read_ea_val() where applicable to
improve code readability and avoid errors like in the past.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 99 +++++++++++++++++++++++----------------------
 1 file changed, 51 insertions(+), 48 deletions(-)

Changes since v1:
Fixed use of wrong variable in debug output within gsm_dlci_data().

Link: https://lore.kernel.org/all/202208222147.WfFRmf1r-lkp@intel.com/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index ed399d57b197..9535e84f3063 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1418,18 +1418,13 @@ static void gsm_control_modem(struct gsm_mux *gsm, const u8 *data, int clen)
 	unsigned int modem = 0;
 	struct gsm_dlci *dlci;
 	int len = clen;
-	int slen;
+	int cl = clen;
 	const u8 *dp = data;
 	struct tty_struct *tty;
 
-	while (gsm_read_ea(&addr, *dp++) == 0) {
-		len--;
-		if (len == 0)
-			return;
-	}
-	/* Must be at least one byte following the EA */
-	len--;
-	if (len <= 0)
+	len = gsm_read_ea_val(&addr, data, cl);
+
+	if (len < 1)
 		return;
 
 	addr >>= 1;
@@ -1438,15 +1433,21 @@ static void gsm_control_modem(struct gsm_mux *gsm, const u8 *data, int clen)
 		return;
 	dlci = gsm->dlci[addr];
 
-	slen = len;
-	while (gsm_read_ea(&modem, *dp++) == 0) {
-		len--;
-		if (len == 0)
-			return;
-	}
-	len--;
+	/* Must be at least one byte following the EA */
+	if ((cl - len) < 1)
+		return;
+
+	dp += len;
+	cl -= len;
+
+	/* get the modem status */
+	len = gsm_read_ea_val(&modem, dp, cl);
+
+	if (len < 1)
+		return;
+
 	tty = tty_port_tty_get(&dlci->port);
-	gsm_process_modem(tty, dlci, modem, slen - len);
+	gsm_process_modem(tty, dlci, modem, cl);
 	if (tty) {
 		tty_wakeup(tty);
 		tty_kref_put(tty);
@@ -1921,11 +1922,10 @@ static void gsm_dlci_data(struct gsm_dlci *dlci, const u8 *data, int clen)
 	struct tty_port *port = &dlci->port;
 	struct tty_struct *tty;
 	unsigned int modem = 0;
-	int len = clen;
-	int slen = 0;
+	int len;
 
 	if (debug & 16)
-		pr_debug("%d bytes for tty\n", len);
+		pr_debug("%d bytes for tty\n", clen);
 	switch (dlci->adaption)  {
 	/* Unsupported types */
 	case 4:		/* Packetised interruptible data */
@@ -1933,24 +1933,22 @@ static void gsm_dlci_data(struct gsm_dlci *dlci, const u8 *data, int clen)
 	case 3:		/* Packetised uininterruptible voice/data */
 		break;
 	case 2:		/* Asynchronous serial with line state in each frame */
-		while (gsm_read_ea(&modem, *data++) == 0) {
-			len--;
-			slen++;
-			if (len == 0)
-				return;
-		}
-		len--;
-		slen++;
+		len = gsm_read_ea_val(&modem, data, clen);
+		if (len < 1)
+			return;
 		tty = tty_port_tty_get(port);
 		if (tty) {
-			gsm_process_modem(tty, dlci, modem, slen);
+			gsm_process_modem(tty, dlci, modem, len);
 			tty_wakeup(tty);
 			tty_kref_put(tty);
 		}
+		/* Skip processed modem data */
+		data += len;
+		clen -= len;
 		fallthrough;
 	case 1:		/* Line state will go via DLCI 0 controls only */
 	default:
-		tty_insert_flip_string(port, data, len);
+		tty_insert_flip_string(port, data, clen);
 		tty_flip_buffer_push(port);
 	}
 }
@@ -1971,24 +1969,29 @@ static void gsm_dlci_command(struct gsm_dlci *dlci, const u8 *data, int len)
 {
 	/* See what command is involved */
 	unsigned int command = 0;
-	while (len-- > 0) {
-		if (gsm_read_ea(&command, *data++) == 1) {
-			int clen = *data++;
-			len--;
-			/* FIXME: this is properly an EA */
-			clen >>= 1;
-			/* Malformed command ? */
-			if (clen > len)
-				return;
-			if (command & 1)
-				gsm_control_message(dlci->gsm, command,
-								data, clen);
-			else
-				gsm_control_response(dlci->gsm, command,
-								data, clen);
-			return;
-		}
-	}
+	const u8 *dp = data;
+	int clen = 0;
+	int dlen;
+
+	/* read the command */
+	dlen = gsm_read_ea_val(&command, dp, len);
+	len -= dlen;
+	dp += dlen;
+
+	/* read any control data */
+	dlen = gsm_read_ea_val(&clen, dp, len);
+	len -= dlen;
+	dp += dlen;
+
+	/* Malformed command? */
+	if (clen > len)
+		return;
+
+	if (command & 1)
+		gsm_control_message(dlci->gsm, command, dp, clen);
+	else
+		gsm_control_response(dlci->gsm, command, dp, clen);
+	return;
 }
 
 /**
-- 
2.34.1

[PATCH v2 4/6] tty: n_gsm: introduce gsm_control_command() function

[D. Starke]

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

Move the content of gsm_control_transmit() to a new function
gsm_control_command() with a more generic signature and analog to
gsm_control_reply(). Use this within gsm_control_transmit().

This is needed to simplify upcoming functional additions.

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 30 +++++++++++++++++++++++-------
 1 file changed, 23 insertions(+), 7 deletions(-)

No changes since v1.

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 9535e84f3063..5a20561c0a5d 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1316,6 +1316,28 @@ static void gsm_dlci_data_kick(struct gsm_dlci *dlci)
  */
 
 
+/**
+ *	gsm_control_command	-	send a command frame to a control
+ *	@gsm: gsm channel
+ *	@cmd: the command to use
+ *	@data: data to follow encoded info
+ *	@dlen: length of data
+ *
+ *	Encode up and queue a UI/UIH frame containing our command.
+ */
+static int gsm_control_command(struct gsm_mux *gsm, int cmd, u8 *data, int dlen)
+{
+	struct gsm_msg *msg = gsm_data_alloc(gsm, 0, dlen + 2, gsm->ftype);
+
+	if (msg == NULL)
+		return -ENOMEM;
+	msg->data[0] = (cmd << 1) | CR | EA;	/* Set C/R */
+	msg->data[1] = (dlen << 1) | EA;
+	memcpy(msg->data + 2, data, dlen);
+	gsm_data_queue(gsm->dlci[0], msg);
+	return 0;
+}
+
 /**
  *	gsm_control_reply	-	send a response frame to a control
  *	@gsm: gsm channel
@@ -1623,13 +1645,7 @@ static void gsm_control_response(struct gsm_mux *gsm, unsigned int command,
 
 static void gsm_control_transmit(struct gsm_mux *gsm, struct gsm_control *ctrl)
 {
-	struct gsm_msg *msg = gsm_data_alloc(gsm, 0, ctrl->len + 2, gsm->ftype);
-	if (msg == NULL)
-		return;
-	msg->data[0] = (ctrl->cmd << 1) | CR | EA;	/* command */
-	msg->data[1] = (ctrl->len << 1) | EA;
-	memcpy(msg->data + 2, ctrl->data, ctrl->len);
-	gsm_data_queue(gsm->dlci[0], msg);
+	gsm_control_command(gsm, ctrl->cmd, ctrl->data, ctrl->len);
 }
 
 /**
-- 
2.34.1

[PATCH v2 5/6] tty: n_gsm: name the debug bits

[D. Starke]

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

Introduce defines to name the various debug bits used within the code to
improve readability and to make its specific use clear.

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

No changes since v1.

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 5a20561c0a5d..fcf2d52d5095 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -63,6 +63,13 @@
 static int debug;
 module_param(debug, int, 0600);
 
+/* Module debug bits */
+#define DBG_DUMP	(1 << 0) /* Data transmission dump. */
+#define DBG_CD_ON	(1 << 1) /* Always assume CD line on. */
+#define DBG_DATA	(1 << 2) /* Data transmission details. */
+#define DBG_ERRORS	(1 << 3) /* Details for fail conditions. */
+#define DBG_TTY		(1 << 4) /* Transmission statistics for DLCI TTYs. */
+
 /* Defaults: these are from the specification */
 
 #define T1	10		/* 100mS */
@@ -535,7 +542,7 @@ static int gsm_register_devices(struct tty_driver *driver, unsigned int index)
 		 */
 		dev = tty_register_device(gsm_tty_driver, base + i, NULL);
 		if (IS_ERR(dev)) {
-			if (debug & 8)
+			if (debug & DBG_ERRORS)
 				pr_info("%s failed to register device minor %u",
 					__func__, base + i);
 			for (i--; i >= 1; i--)
@@ -589,7 +596,7 @@ static void gsm_unregister_devices(struct tty_driver *driver,
 static void gsm_print_packet(const char *hdr, int addr, int cr,
 					u8 control, const u8 *data, int dlen)
 {
-	if (!(debug & 1))
+	if (!(debug & DBG_DUMP))
 		return;
 
 	pr_info("%s %d) %c: ", hdr, addr, "RC"[cr]);
@@ -833,7 +840,7 @@ static int gsm_send_packet(struct gsm_mux *gsm, struct gsm_msg *msg)
 		len += 2;
 	}
 
-	if (debug & 4)
+	if (debug & DBG_DATA)
 		gsm_hex_dump_bytes(__func__, gsm->txframe, len);
 	gsm_print_packet("-->", msg->addr, gsm->initiator, msg->ctrl, msg->data,
 			 msg->len);
@@ -1765,7 +1772,7 @@ static int gsm_control_wait(struct gsm_mux *gsm, struct gsm_control *control)
 static void gsm_dlci_close(struct gsm_dlci *dlci)
 {
 	del_timer(&dlci->t1);
-	if (debug & 8)
+	if (debug & DBG_ERRORS)
 		pr_debug("DLCI %d goes closed.\n", dlci->addr);
 	dlci->state = DLCI_CLOSED;
 	/* Prevent us from sending data before the link is up again */
@@ -1799,7 +1806,7 @@ static void gsm_dlci_open(struct gsm_dlci *dlci)
 	/* This will let a tty open continue */
 	dlci->state = DLCI_OPEN;
 	dlci->constipated = false;
-	if (debug & 8)
+	if (debug & DBG_ERRORS)
 		pr_debug("DLCI %d goes open.\n", dlci->addr);
 	/* Send current modem state */
 	if (dlci->addr)
@@ -1835,7 +1842,7 @@ static void gsm_dlci_t1(struct timer_list *t)
 			gsm_command(dlci->gsm, dlci->addr, SABM|PF);
 			mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
 		} else if (!dlci->addr && gsm->control == (DM | PF)) {
-			if (debug & 8)
+			if (debug & DBG_ERRORS)
 				pr_info("DLCI %d opening in ADM mode.\n",
 					dlci->addr);
 			dlci->mode = DLCI_MODE_ADM;
@@ -1940,7 +1947,7 @@ static void gsm_dlci_data(struct gsm_dlci *dlci, const u8 *data, int clen)
 	unsigned int modem = 0;
 	int len;
 
-	if (debug & 16)
+	if (debug & DBG_TTY)
 		pr_debug("%d bytes for tty\n", clen);
 	switch (dlci->adaption)  {
 	/* Unsupported types */
@@ -2030,7 +2037,7 @@ static void gsm_kick_timer(struct timer_list *t)
 		sent = gsm_dlci_data_sweep(gsm);
 	spin_unlock_irqrestore(&gsm->tx_lock, flags);
 
-	if (sent && debug & 4)
+	if (sent && debug & DBG_DATA)
 		pr_info("%s TX queue stalled\n", __func__);
 }
 
@@ -2164,7 +2171,7 @@ static void gsm_queue(struct gsm_mux *gsm)
 
 	if (gsm->fcs != GOOD_FCS) {
 		gsm->bad_fcs++;
-		if (debug & 4)
+		if (debug & DBG_DATA)
 			pr_debug("BAD FCS %02x\n", gsm->fcs);
 		return;
 	}
@@ -2790,7 +2797,7 @@ static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len)
 		set_bit(TTY_DO_WRITE_WAKEUP, &gsm->tty->flags);
 		return -ENOSPC;
 	}
-	if (debug & 4)
+	if (debug & DBG_DATA)
 		gsm_hex_dump_bytes(__func__, data, len);
 	return gsm->tty->ops->write(gsm->tty, data, len);
 }
@@ -2877,7 +2884,7 @@ static void gsmld_receive_buf(struct tty_struct *tty, const unsigned char *cp,
 	struct gsm_mux *gsm = tty->disc_data;
 	char flags = TTY_NORMAL;
 
-	if (debug & 4)
+	if (debug & DBG_DATA)
 		gsm_hex_dump_bytes(__func__, cp, count);
 
 	for (; count; count--, cp++) {
@@ -3416,7 +3423,7 @@ static int gsm_carrier_raised(struct tty_port *port)
 	/* Not yet open so no carrier info */
 	if (dlci->state != DLCI_OPEN)
 		return 0;
-	if (debug & 2)
+	if (debug & DBG_CD_ON)
 		return 1;
 
 	/*
-- 
2.34.1

[PATCH v2 6/6] tty: n_gsm: add debug bit for user payload

[D. Starke]

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

A debug bit to output a complete transmission dump exists. Sometimes only
the user frames are relevant. Add an additional bit which limits the
transmission dump output to user data frames if set.

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
 drivers/tty/n_gsm.c | 5 +++++
 1 file changed, 5 insertions(+)

No changes since v1.

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index fcf2d52d5095..f3f0668f0a73 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -69,6 +69,7 @@ module_param(debug, int, 0600);
 #define DBG_DATA	(1 << 2) /* Data transmission details. */
 #define DBG_ERRORS	(1 << 3) /* Details for fail conditions. */
 #define DBG_TTY		(1 << 4) /* Transmission statistics for DLCI TTYs. */
+#define DBG_PAYLOAD	(1 << 5) /* Limits DBG_DUMP to payload frames. */
 
 /* Defaults: these are from the specification */
 
@@ -598,6 +599,10 @@ static void gsm_print_packet(const char *hdr, int addr, int cr,
 {
 	if (!(debug & DBG_DUMP))
 		return;
+	/* Only show user payload frames if debug & DBG_PAYLOAD */
+	if (!(debug & DBG_PAYLOAD) && addr != 0)
+		if ((control & ~PF) == UI || (control & ~PF) == UIH)
+			return;
 
 	pr_info("%s %d) %c: ", hdr, addr, "RC"[cr]);
 
-- 
2.34.1

Re: [PATCH v2 1/6] tty: n_gsm: add enumeration for gsm encodings

[Jiri Slaby]

On 23. 08. 22, 8:22, D. Starke wrote:
> From: Daniel Starke <daniel.starke@siemens.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)
> 
> Also remove redundant configuration in gsmld_open(). The same value is
> already set in gsm_alloc_mux() which is also called in gsmld_open().
> 
> Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
> ---
>   drivers/tty/n_gsm.c | 31 +++++++++++++++++--------------
>   1 file changed, 17 insertions(+), 14 deletions(-)
> 
> No changes since v1.
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index caa5c14ed57f..5bf09d129357 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
...
> @@ -2651,7 +2656,7 @@ static void gsm_copy_config_values(struct gsm_mux *gsm,
>   {
>   	memset(c, 0, sizeof(*c));
>   	c->adaption = gsm->adaption;
> -	c->encapsulation = gsm->encoding;
> +	c->encapsulation = (int)gsm->encoding;

IIRC, the C standard says enum behave like int. So why is the cast needed?

>   	c->initiator = gsm->initiator;
>   	c->t1 = gsm->t1;
>   	c->t2 = gsm->t2;
...
> @@ -2942,8 +2947,6 @@ static int gsmld_open(struct tty_struct *tty)
>   	tty->receive_room = 65536;
>   
>   	/* Attach the initial passive connection */
> -	gsm->encoding = 1;
> -

This doesn't relate to "add enumeration for gsm encodings". Why do you 
remove this line?

>   	gsmld_attach_gsm(tty, gsm);

thanks,
-- 
js
suse labs

Re: [PATCH v2 2/6] tty: n_gsm: name gsm tty device minors

[Jiri Slaby]

On 23. 08. 22, 8:22, D. Starke wrote:
> From: Daniel Starke <daniel.starke@siemens.com>
> 
> Add a macro which defines the possible number of virtual devices for n_gsm
> to improve code readability.

Reviewed-by: Jiri Slaby <jirislaby@kernel.org>

> Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
> ---
>   drivers/tty/n_gsm.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> No changes since v1.
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 5bf09d129357..ed399d57b197 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -164,6 +164,9 @@ struct gsm_dlci {
>   	struct net_device *net; /* network interface, if created */
>   };
>   
> +/* Total number of supported devices */
> +#define GSM_TTY_MINORS		256
> +
>   /* DLCI 0, 62/63 are special or reserved see gsmtty_open */
>   
>   #define NUM_DLCI		64
> @@ -3748,7 +3751,7 @@ static int __init gsm_init(void)
>   		return status;
>   	}
>   
> -	gsm_tty_driver = tty_alloc_driver(256, TTY_DRIVER_REAL_RAW |
> +	gsm_tty_driver = tty_alloc_driver(GSM_TTY_MINORS, TTY_DRIVER_REAL_RAW |
>   			TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_HARDWARE_BREAK);
>   	if (IS_ERR(gsm_tty_driver)) {
>   		pr_err("gsm_init: tty allocation failed.\n");

-- 
js
suse labs

Re: [PATCH v2 3/6] tty: n_gsm: replace use of gsm_read_ea() with gsm_read_ea_val()

[Jiri Slaby]

On 23. 08. 22, 8:22, D. Starke wrote:
> From: Daniel Starke <daniel.starke@siemens.com>
> 
> Replace the use of gsm_read_ea() with gsm_read_ea_val() where applicable to
> improve code readability and avoid errors like in the past.

What errors?

> Reported-by: kernel test robot <lkp@intel.com>

Perhaps you have a link?

> Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
> ---
>   drivers/tty/n_gsm.c | 99 +++++++++++++++++++++++----------------------
>   1 file changed, 51 insertions(+), 48 deletions(-)
> 
> Changes since v1:
> Fixed use of wrong variable in debug output within gsm_dlci_data().
> 
> Link: https://lore.kernel.org/all/202208222147.WfFRmf1r-lkp@intel.com/

Ah, you do. This should have been above...

> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index ed399d57b197..9535e84f3063 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -1418,18 +1418,13 @@ static void gsm_control_modem(struct gsm_mux *gsm, const u8 *data, int clen)
>   	unsigned int modem = 0;
>   	struct gsm_dlci *dlci;
>   	int len = clen;
> -	int slen;
> +	int cl = clen;
>   	const u8 *dp = data;
>   	struct tty_struct *tty;
>   
> -	while (gsm_read_ea(&addr, *dp++) == 0) {
> -		len--;
> -		if (len == 0)
> -			return;
> -	}
> -	/* Must be at least one byte following the EA */
> -	len--;
> -	if (len <= 0)
> +	len = gsm_read_ea_val(&addr, data, cl);
> +

There should be likely no extra \n here between assignment and check of 
the value (len).

> +	if (len < 1)
>   		return;
>   
>   	addr >>= 1;
> @@ -1438,15 +1433,21 @@ static void gsm_control_modem(struct gsm_mux *gsm, const u8 *data, int clen)
>   		return;
>   	dlci = gsm->dlci[addr];
>   
> -	slen = len;
> -	while (gsm_read_ea(&modem, *dp++) == 0) {
> -		len--;
> -		if (len == 0)
> -			return;
> -	}
> -	len--;
> +	/* Must be at least one byte following the EA */
> +	if ((cl - len) < 1)
> +		return;
> +
> +	dp += len;
> +	cl -= len;
> +
> +	/* get the modem status */
> +	len = gsm_read_ea_val(&modem, dp, cl);
> +
> +	if (len < 1)

The same here.

> +		return;
> +
>   	tty = tty_port_tty_get(&dlci->port);
> -	gsm_process_modem(tty, dlci, modem, slen - len);
> +	gsm_process_modem(tty, dlci, modem, cl);
>   	if (tty) {
>   		tty_wakeup(tty);
>   		tty_kref_put(tty);
> @@ -1921,11 +1922,10 @@ static void gsm_dlci_data(struct gsm_dlci *dlci, const u8 *data, int clen)
>   	struct tty_port *port = &dlci->port;
>   	struct tty_struct *tty;
>   	unsigned int modem = 0;
> -	int len = clen;
> -	int slen = 0;
> +	int len;
>   
>   	if (debug & 16)
> -		pr_debug("%d bytes for tty\n", len);
> +		pr_debug("%d bytes for tty\n", clen);
>   	switch (dlci->adaption)  {
>   	/* Unsupported types */
>   	case 4:		/* Packetised interruptible data */
> @@ -1933,24 +1933,22 @@ static void gsm_dlci_data(struct gsm_dlci *dlci, const u8 *data, int clen)
>   	case 3:		/* Packetised uininterruptible voice/data */
>   		break;
>   	case 2:		/* Asynchronous serial with line state in each frame */
> -		while (gsm_read_ea(&modem, *data++) == 0) {
> -			len--;
> -			slen++;
> -			if (len == 0)
> -				return;
> -		}
> -		len--;
> -		slen++;
> +		len = gsm_read_ea_val(&modem, data, clen);
> +		if (len < 1)
> +			return;
>   		tty = tty_port_tty_get(port);
>   		if (tty) {
> -			gsm_process_modem(tty, dlci, modem, slen);
> +			gsm_process_modem(tty, dlci, modem, len);
>   			tty_wakeup(tty);
>   			tty_kref_put(tty);
>   		}
> +		/* Skip processed modem data */
> +		data += len;
> +		clen -= len;
>   		fallthrough;
>   	case 1:		/* Line state will go via DLCI 0 controls only */
>   	default:
> -		tty_insert_flip_string(port, data, len);
> +		tty_insert_flip_string(port, data, clen);
>   		tty_flip_buffer_push(port);
>   	}
>   }
> @@ -1971,24 +1969,29 @@ static void gsm_dlci_command(struct gsm_dlci *dlci, const u8 *data, int len)
>   {
>   	/* See what command is involved */
>   	unsigned int command = 0;
> -	while (len-- > 0) {
> -		if (gsm_read_ea(&command, *data++) == 1) {
> -			int clen = *data++;
> -			len--;
> -			/* FIXME: this is properly an EA */
> -			clen >>= 1;
> -			/* Malformed command ? */
> -			if (clen > len)
> -				return;
> -			if (command & 1)
> -				gsm_control_message(dlci->gsm, command,
> -								data, clen);
> -			else
> -				gsm_control_response(dlci->gsm, command,
> -								data, clen);
> -			return;
> -		}
> -	}
> +	const u8 *dp = data;

Why is the local "dp" needed?

> +	int clen = 0;
> +	int dlen;

Having lengths signed is mostly confusing. Shouldn't/couldn't they be 
uint instead?

> +	/* read the command */
> +	dlen = gsm_read_ea_val(&command, dp, len);
> +	len -= dlen;
> +	dp += dlen;
> +
> +	/* read any control data */
> +	dlen = gsm_read_ea_val(&clen, dp, len);
> +	len -= dlen;
> +	dp += dlen;
> +
> +	/* Malformed command? */
> +	if (clen > len)
> +		return;
> +
> +	if (command & 1)
> +		gsm_control_message(dlci->gsm, command, dp, clen);
> +	else
> +		gsm_control_response(dlci->gsm, command, dp, clen);
> +	return;

An extra return.

>   }

thanks,
-- 
js
suse labs

Re: [PATCH v2 4/6] tty: n_gsm: introduce gsm_control_command() function

[Jiri Slaby]

On 23. 08. 22, 8:22, D. Starke wrote:
> From: Daniel Starke <daniel.starke@siemens.com>
> 
> Move the content of gsm_control_transmit() to a new function
> gsm_control_command() with a more generic signature and analog to
> gsm_control_reply(). Use this within gsm_control_transmit().
> 
> This is needed to simplify upcoming functional additions.
> 
> Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
> ---
>   drivers/tty/n_gsm.c | 30 +++++++++++++++++++++++-------
>   1 file changed, 23 insertions(+), 7 deletions(-)
> 
> No changes since v1.
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 9535e84f3063..5a20561c0a5d 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -1316,6 +1316,28 @@ static void gsm_dlci_data_kick(struct gsm_dlci *dlci)
>    */
>   
>   
> +/**
> + *	gsm_control_command	-	send a command frame to a control
> + *	@gsm: gsm channel
> + *	@cmd: the command to use
> + *	@data: data to follow encoded info
> + *	@dlen: length of data
> + *
> + *	Encode up and queue a UI/UIH frame containing our command.

These tabs after asterisks are not understood by kernel-doc. You should 
add no new ones.

> + */
> +static int gsm_control_command(struct gsm_mux *gsm, int cmd, u8 *data, int dlen)

Can gsm and data be const? I assume gsm cannot due to call to 
gsm_data_queue(). And what about cmd & dlen being uint? cmd seems to be 
u8 at least...

> +{
> +	struct gsm_msg *msg = gsm_data_alloc(gsm, 0, dlen + 2, gsm->ftype);
> +
> +	if (msg == NULL)
> +		return -ENOMEM;

\n here

> +	msg->data[0] = (cmd << 1) | CR | EA;	/* Set C/R */
> +	msg->data[1] = (dlen << 1) | EA;
> +	memcpy(msg->data + 2, data, dlen);
> +	gsm_data_queue(gsm->dlci[0], msg);

\n here

> +	return 0;
> +}
> +
>   /**
>    *	gsm_control_reply	-	send a response frame to a control
>    *	@gsm: gsm channel
> @@ -1623,13 +1645,7 @@ static void gsm_control_response(struct gsm_mux *gsm, unsigned int command,
>   
>   static void gsm_control_transmit(struct gsm_mux *gsm, struct gsm_control *ctrl)
>   {
> -	struct gsm_msg *msg = gsm_data_alloc(gsm, 0, ctrl->len + 2, gsm->ftype);
> -	if (msg == NULL)
> -		return;
> -	msg->data[0] = (ctrl->cmd << 1) | CR | EA;	/* command */
> -	msg->data[1] = (ctrl->len << 1) | EA;
> -	memcpy(msg->data + 2, ctrl->data, ctrl->len);
> -	gsm_data_queue(gsm->dlci[0], msg);
> +	gsm_control_command(gsm, ctrl->cmd, ctrl->data, ctrl->len);
>   }

thanks,
-- 
js
suse labs

Re: [PATCH v2 5/6] tty: n_gsm: name the debug bits

[Jiri Slaby]

On 23. 08. 22, 8:22, D. Starke wrote:
> From: Daniel Starke <daniel.starke@siemens.com>
> 
> Introduce defines to name the various debug bits used within the code to
> improve readability and to make its specific use clear.
> 
> Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
> ---
>   drivers/tty/n_gsm.c | 31 +++++++++++++++++++------------
>   1 file changed, 19 insertions(+), 12 deletions(-)
> 
> No changes since v1.
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 5a20561c0a5d..fcf2d52d5095 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -63,6 +63,13 @@
>   static int debug;
>   module_param(debug, int, 0600);
>   
> +/* Module debug bits */
> +#define DBG_DUMP	(1 << 0) /* Data transmission dump. */
> +#define DBG_CD_ON	(1 << 1) /* Always assume CD line on. */
> +#define DBG_DATA	(1 << 2) /* Data transmission details. */
> +#define DBG_ERRORS	(1 << 3) /* Details for fail conditions. */
> +#define DBG_TTY		(1 << 4) /* Transmission statistics for DLCI TTYs. */

Could you use BIT() instead?

thanks,
-- 
js
suse labs