Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 6e81c261 authored by Johan Hovold's avatar Johan Hovold Committed by Greg Kroah-Hartman
Browse files

USB: serial: keyspan_pda: fix write unthrottling 



commit 320f9028c7873c3c7710e8e93e5c979f4c857490 upstream.

The driver did not update its view of the available device buffer space
until write() was called in task context. This meant that write_room()
would return 0 even after the device had sent a write-unthrottle
notification, something which could lead to blocked writers not being
woken up (e.g. when using OPOST).

Note that we must also request an unthrottle notification is case a
write() request fills the device buffer exactly.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Cc: stable <stable@vger.kernel.org>
Acked-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e7d77722

drivers/usb/serial/keyspan_pda.c

+20 −9
Original line number Diff line number Diff line
@@ -40,6 +40,8 @@ 
#define DRIVER_AUTHOR "Brian Warner <warner@lothar.com>"

#define DRIVER_DESC "USB Keyspan PDA Converter driver"



#define KEYSPAN_TX_THRESHOLD	16



struct keyspan_pda_private {

	int			tx_room;

	int			tx_throttled;
@@ -110,7 +112,7 @@ static void keyspan_pda_request_unthrottle(struct work_struct *work) 
				 7, /* request_unthrottle */

				 USB_TYPE_VENDOR | USB_RECIP_INTERFACE

				 | USB_DIR_OUT,

				 16, /* value: threshold */

				 KEYSPAN_TX_THRESHOLD,

				 0, /* index */

				 NULL,

				 0,
@@ -129,6 +131,8 @@ static void keyspan_pda_rx_interrupt(struct urb *urb) 
	int retval;

	int status = urb->status;

	struct keyspan_pda_private *priv;

	unsigned long flags;



	priv = usb_get_serial_port_data(port);



	switch (status) {
@@ -171,7 +175,10 @@ static void keyspan_pda_rx_interrupt(struct urb *urb) 
		case 1: /* modemline change */

			break;

		case 2: /* tx unthrottle interrupt */

			spin_lock_irqsave(&port->lock, flags);

			priv->tx_throttled = 0;

			priv->tx_room = max(priv->tx_room, KEYSPAN_TX_THRESHOLD);

			spin_unlock_irqrestore(&port->lock, flags);

			/* queue up a wakeup at scheduler time */

			usb_serial_port_softint(port);

			break;
@@ -505,7 +512,8 @@ static int keyspan_pda_write(struct tty_struct *tty, 
			goto exit;

		}

	}

	if (count > priv->tx_room) {



	if (count >= priv->tx_room) {

		/* we're about to completely fill the Tx buffer, so

		   we'll be throttled afterwards. */

		count = priv->tx_room;
@@ -560,14 +568,17 @@ static void keyspan_pda_write_bulk_callback(struct urb *urb) 
static int keyspan_pda_write_room(struct tty_struct *tty)

{

	struct usb_serial_port *port = tty->driver_data;

	struct keyspan_pda_private *priv;

	priv = usb_get_serial_port_data(port);

	/* used by n_tty.c for processing of tabs and such. Giving it our

	   conservative guess is probably good enough, but needs testing by

	   running a console through the device. */

	return priv->tx_room;

}

	struct keyspan_pda_private *priv = usb_get_serial_port_data(port);

	unsigned long flags;

	int room = 0;



	spin_lock_irqsave(&port->lock, flags);

	if (test_bit(0, &port->write_urbs_free) && !priv->tx_throttled)

		room = priv->tx_room;

	spin_unlock_irqrestore(&port->lock, flags);



	return room;

}



static int keyspan_pda_chars_in_buffer(struct tty_struct *tty)

{