[PATCH 0/2] hso: refcounting and termios bits

[PATCH 0/2] hso: refcounting and termios bits

[Alan Cox]

Bring the HSO driver into line with the latest features and tidy the termios
handling. These are patches for comment and ad{oa}ption by the maintainer of
the driver rather than for application.

Alan

---

Alan Cox (2):
      tty: Fix the HSO termios handling a bit
      hso: net driver using tty without locking


 drivers/net/usb/hso.c |  103 +++++++++++++++++++++++++++++++++----------------
 1 files changed, 70 insertions(+), 33 deletions(-)

-- 
	"Yeah, back in the good old days the rich were much freer from
		the burden of the poor."
				-- Michael Foord

[PATCH 1/2] hso: net driver using tty without locking

[Alan Cox]

From: Alan Cox <alan@redhat.com>

Checking tty == NULL doesn't help us unless we have a clear semantic for
the locking of the tty object in the driver. Use the tty kref objects so that
we can take references to the tty in the USB event handling paths.

Signed-off-by: Alan Cox <alan@redhat.com>
---

 drivers/net/usb/hso.c |   54 ++++++++++++++++++++++++++++++++++++++-----------
 1 files changed, 42 insertions(+), 12 deletions(-)


diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index 8e90891..4398289 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -1011,7 +1011,7 @@ static void _hso_serial_set_termios(struct tty_struct *tty,
 	struct hso_serial *serial = get_serial_by_tty(tty);
 	struct ktermios *termios;
 
-	if ((!tty) || (!tty->termios) || (!serial)) {
+	if (!serial) {
 		printk(KERN_ERR "%s: no tty structures", __func__);
 		return;
 	}
@@ -1053,14 +1053,14 @@ static void _hso_serial_set_termios(struct tty_struct *tty,
 	termios->c_cflag |= CS8;	/* character size 8 bits */
 
 	/* baud rate 115200 */
-	tty_encode_baud_rate(serial->tty, 115200, 115200);
+	tty_encode_baud_rate(tty, 115200, 115200);
 
 	/*
 	 * Force low_latency on; otherwise the pushes are scheduled;
 	 * this is bad as it opens up the possibility of dropping bytes
 	 * on the floor.  We don't want to drop bytes on the floor. :)
 	 */
-	serial->tty->low_latency = 1;
+	tty->low_latency = 1;
 	return;
 }
 
@@ -1224,6 +1224,7 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
 
 	/* sanity check */
 	if (serial == NULL || serial->magic != HSO_SERIAL_MAGIC) {
+		WARN_ON(1);
 		tty->driver_data = NULL;
 		D1("Failed to open port");
 		return -ENODEV;
@@ -1238,8 +1239,10 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
 	kref_get(&serial->parent->ref);
 
 	/* setup */
+	spin_lock_irq(&serial->serial_lock);
 	tty->driver_data = serial;
-	serial->tty = tty;
+	serial->tty = tty_kref_get(tty);
+	spin_unlock_irq(&serial->serial_lock);
 
 	/* check for port already opened, if not set the termios */
 	serial->open_count++;
@@ -1281,6 +1284,10 @@ static void hso_serial_close(struct tty_struct *tty, struct file *filp)
 
 	D1("Closing serial port");
 
+	/* Open failed, no close cleanup required */
+	if (serial == NULL)
+		return;
+
 	mutex_lock(&serial->parent->mutex);
 	usb_gone = serial->parent->usb_gone;
 
@@ -1293,10 +1300,13 @@ static void hso_serial_close(struct tty_struct *tty, struct file *filp)
 	kref_put(&serial->parent->ref, hso_serial_ref_free);
 	if (serial->open_count <= 0) {
 		serial->open_count = 0;
-		if (serial->tty) {
+		spin_lock_irq(&serial->serial_lock);
+		if (serial->tty == tty) {
 			serial->tty->driver_data = NULL;
 			serial->tty = NULL;
+			tty_kref_put(tty);
 		}
+		spin_unlock_irq(&serial->serial_lock);
 		if (!usb_gone)
 			hso_stop_serial_device(serial->parent);
 		tasklet_kill(&serial->unthrottle_tasklet);
@@ -1649,6 +1659,7 @@ static void hso_std_serial_write_bulk_callback(struct urb *urb)
 {
 	struct hso_serial *serial = urb->context;
 	int status = urb->status;
+	struct tty_struct *tty;
 
 	/* sanity check */
 	if (!serial) {
@@ -1658,14 +1669,18 @@ static void hso_std_serial_write_bulk_callback(struct urb *urb)
 
 	spin_lock(&serial->serial_lock);
 	serial->tx_urb_used = 0;
+	tty = tty_kref_get(serial->tty);
 	spin_unlock(&serial->serial_lock);
 	if (status) {
 		log_usb_status(status, __func__);
+		tty_kref_put(tty);
 		return;
 	}
 	hso_put_activity(serial->parent);
-	if (serial->tty)
-		tty_wakeup(serial->tty);
+	if (tty) {
+		tty_wakeup(tty);
+		tty_kref_put(tty);
+	}
 	hso_kick_transmit(serial);
 
 	D1(" ");
@@ -1702,6 +1717,7 @@ static void ctrl_callback(struct urb *urb)
 	struct hso_serial *serial = urb->context;
 	struct usb_ctrlrequest *req;
 	int status = urb->status;
+	struct tty_struct *tty;
 
 	/* sanity check */
 	if (!serial)
@@ -1709,9 +1725,11 @@ static void ctrl_callback(struct urb *urb)
 
 	spin_lock(&serial->serial_lock);
 	serial->tx_urb_used = 0;
+	tty = tty_kref_get(serial->tty);
 	spin_unlock(&serial->serial_lock);
 	if (status) {
 		log_usb_status(status, __func__);
+		tty_kref_put(tty);
 		return;
 	}
 
@@ -1730,25 +1748,31 @@ static void ctrl_callback(struct urb *urb)
 		spin_unlock(&serial->serial_lock);
 	} else {
 		hso_put_activity(serial->parent);
-		if (serial->tty)
-			tty_wakeup(serial->tty);
+		if (tty)
+			tty_wakeup(tty);
 		/* response to a write command */
 		hso_kick_transmit(serial);
 	}
+	tty_kref_put(tty);
 }
 
 /* handle RX data for serial port */
 static int put_rxbuf_data(struct urb *urb, struct hso_serial *serial)
 {
-	struct tty_struct *tty = serial->tty;
+	struct tty_struct *tty;
 	int write_length_remaining = 0;
 	int curr_write_len;
+
 	/* Sanity check */
 	if (urb == NULL || serial == NULL) {
 		D1("serial = NULL");
 		return -2;
 	}
 
+	spin_lock(&serial->serial_lock);
+	tty = tty_kref_get(serial->tty);
+	spin_unlock(&serial->serial_lock);
+
 	/* Push data to tty */
 	if (tty) {
 		write_length_remaining = urb->actual_length -
@@ -1770,6 +1794,7 @@ static int put_rxbuf_data(struct urb *urb, struct hso_serial *serial)
 		serial->curr_rx_urb_offset = 0;
 		serial->rx_urb_filled[hso_urb_to_index(serial, urb)] = 0;
 	}
+	tty_kref_put(tty);
 	return write_length_remaining;
 }
 
@@ -2779,15 +2804,20 @@ static void hso_serial_ref_free(struct kref *ref)
 static void hso_free_interface(struct usb_interface *interface)
 {
 	struct hso_serial *hso_dev;
+	struct tty_struct *tty;
 	int i;
 
 	for (i = 0; i < HSO_SERIAL_TTY_MINORS; i++) {
 		if (serial_table[i]
 		    && (serial_table[i]->interface == interface)) {
 			hso_dev = dev2ser(serial_table[i]);
-			if (hso_dev->tty)
-				tty_hangup(hso_dev->tty);
+			spin_lock_irq(&hso_dev->serial_lock);
+			tty = tty_kref_get(hso_dev->tty);
+			spin_unlock_irq(&hso_dev->serial_lock);
+			if (tty)
+				tty_hangup(tty);
 			mutex_lock(&hso_dev->parent->mutex);
+			tty_kref_put(tty);
 			hso_dev->parent->usb_gone = 1;
 			mutex_unlock(&hso_dev->parent->mutex);
 			kref_put(&serial_table[i]->ref, hso_serial_ref_free);

[PATCH 2/2] tty: Fix the HSO termios handling a bit

[Alan Cox]

From: Alan Cox <alan@redhat.com>

Init the tty structure once
Don't set ->low_latency twice in a row
Don't force bits we should be leaving to the user
Don't allocate termios arrays as these are in fact allocated by the tty layer
for you and just overwrite the ones allocated in the driver

Signed-off-by: Alan Cox <alan@redhat.com>
---

 drivers/net/usb/hso.c |   55 ++++++++++++++++++++++++++++---------------------
 1 files changed, 31 insertions(+), 24 deletions(-)


diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index 4398289..89f0d67 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -362,8 +362,6 @@ static struct tty_driver *tty_drv;
 static struct hso_device *serial_table[HSO_SERIAL_TTY_MINORS];
 static struct hso_device *network_table[HSO_MAX_NET_DEVICES];
 static spinlock_t serial_table_lock;
-static struct ktermios *hso_serial_termios[HSO_SERIAL_TTY_MINORS];
-static struct ktermios *hso_serial_termios_locked[HSO_SERIAL_TTY_MINORS];
 
 static const s32 default_port_spec[] = {
 	HSO_INTF_MUX | HSO_PORT_NETWORK,
@@ -1005,23 +1003,11 @@ static void read_bulk_callback(struct urb *urb)
 
 /* Serial driver functions */
 
-static void _hso_serial_set_termios(struct tty_struct *tty,
-				    struct ktermios *old)
+static void hso_init_termios(struct ktermios *termios)
 {
-	struct hso_serial *serial = get_serial_by_tty(tty);
-	struct ktermios *termios;
-
-	if (!serial) {
-		printk(KERN_ERR "%s: no tty structures", __func__);
-		return;
-	}
-
-	D4("port %d", serial->minor);
-
 	/*
 	 * The default requirements for this device are:
 	 */
-	termios = tty->termios;
 	termios->c_iflag &=
 		~(IGNBRK	/* disable ignore break */
 		| BRKINT	/* disable break causes interrupt */
@@ -1053,15 +1039,38 @@ static void _hso_serial_set_termios(struct tty_struct *tty,
 	termios->c_cflag |= CS8;	/* character size 8 bits */
 
 	/* baud rate 115200 */
-	tty_encode_baud_rate(tty, 115200, 115200);
+	tty_termios_encode_baud_rate(termios, 115200, 115200);
+}
+
+static void _hso_serial_set_termios(struct tty_struct *tty,
+				    struct ktermios *old)
+{
+	struct hso_serial *serial = get_serial_by_tty(tty);
+	struct ktermios *termios;
+
+	if (!serial) {
+		printk(KERN_ERR "%s: no tty structures", __func__);
+		return;
+	}
+
+	D4("port %d", serial->minor);
 
 	/*
-	 * Force low_latency on; otherwise the pushes are scheduled;
-	 * this is bad as it opens up the possibility of dropping bytes
-	 * on the floor.  We don't want to drop bytes on the floor. :)
+	 *	Fix up unsupported bits
 	 */
-	tty->low_latency = 1;
-	return;
+	termios = tty->termios;
+	termios->c_iflag &= ~IXON; /* disable enable XON/XOFF flow control */
+
+	termios->c_cflag &=
+		~(CSIZE		/* no size */
+		| PARENB	/* disable parity bit */
+		| CBAUD		/* clear current baud rate */
+		| CBAUDEX);	/* clear current buad rate */
+
+	termios->c_cflag |= CS8;	/* character size 8 bits */
+
+	/* baud rate 115200 */
+	tty_encode_baud_rate(tty, 115200, 115200);
 }
 
 static void hso_resubmit_rx_bulk_urb(struct hso_serial *serial, struct urb *urb)
@@ -2961,9 +2970,7 @@ static int __init hso_init(void)
 	tty_drv->subtype = SERIAL_TYPE_NORMAL;
 	tty_drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
 	tty_drv->init_termios = tty_std_termios;
-	tty_drv->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL;
-	tty_drv->termios = hso_serial_termios;
-	tty_drv->termios_locked = hso_serial_termios_locked;
+	hso_init_termios(&tty_drv->init_termios);
 	tty_set_operations(tty_drv, &hso_serial_ops);
 
 	/* register the tty driver */