[PATCH] WhiteHEAT update

1-fix-lowlat:

QA found that running all four ports at 460800 would drop data. I
traced it to data being dropped in the read callback because the flip
buffers were full. Turning on the low latency flag fixed things.

2-fix-taint

A side-effect of turning on low latency; the interrupt context from
the callback is now passed through to the tty layer, passing it on to
calls back into usb-serial.c. Which causes deadlocks when trying to
re-acquire the per-port semaphore. We've already talked about this.
This patch is my work-around for the usb-serial.c brokenness.
Basically, implemement a buffering scheme, and schedule a software
interrupt to handle the data handoff to the tty layer sometime later.
urb_pool_size defaults to 8, but is a module parameter and can be
modified at runtime.
The buffering is needed so that the driver can run while data is
waiting to be processed, but I could have used the tty layer
scheduling instead of doing my own by turning off low latency.
However, I looked at the tty layer and it seems to me that there's
nothing preventing a really fast device from flipping one buffer,
flipping the next, and flipping back to the still full buffer from
before (actually, the flip just gets scheduled for later), so my
driver needs to be able to hold onto buffered data and schedule them
for processing later anyway. So, might as well leave low_latency on.


diff -Naur linux-2.5.49-0-virgin/drivers/usb/serial/whiteheat.c linux-2.5.49-1-fix-
lowlat/drivers/usb/serial/whiteheat.c

drivers/usb/serial/whiteheat.c

@@ -202,10 +202,23 @@ struct whiteheat_command_private {
 #define THROTTLED		0x01
 #define ACTUALLY_THROTTLED	0x02
 
+static int urb_pool_size = 8;
+
+struct whiteheat_urb_wrap {
+	struct list_head	list;
+	struct urb		*urb;
+};
+
 struct whiteheat_private {
 	spinlock_t		lock;
 	__u8			flags;
 	__u8			mcr;
+	struct list_head	rx_urbs_free;
+	struct list_head	rx_urbs_submitted;
+	struct list_head	rx_urb_q;
+	struct work_struct	rx_work;
+	struct list_head	tx_urbs_free;
+	struct list_head	tx_urbs_submitted;
 };
 
 
@@ -215,6 +228,11 @@ static void stop_command_port(struct usb_serial *serial);
 static void command_port_write_callback(struct urb *urb);
 static void command_port_read_callback(struct urb *urb);
 
+static int start_port_read(struct usb_serial_port *port);
+static struct whiteheat_urb_wrap *urb_to_wrap(struct urb *urb, struct list_head *head);
+static struct list_head *list_first(struct list_head *head);
+static void rx_data_softint(void *private);
+
 static int firm_send_command(struct usb_serial_port *port, __u8 command, __u8 *data, __u8 datasize);
 static int firm_open(struct usb_serial_port *port);
 static int firm_close(struct usb_serial_port *port);
@@ -330,6 +348,11 @@ static int whiteheat_attach (struct usb_serial *serial)
 	__u8 command[2] = { WHITEHEAT_GET_HW_INFO, 0 };
 	__u8 result[sizeof(*hw_info) + 1];
 	int i;
+	int j;
+	struct urb *urb;
+	int buf_size;
+	struct whiteheat_urb_wrap *wrap;
+	struct list_head *tmp;
 
 	command_port = &serial->port[COMMAND_PORT];
 
@@ -373,18 +396,80 @@ static int whiteheat_attach (struct usb_serial *serial)
 		port = &serial->port[i];
 
 		info = (struct whiteheat_private *)kmalloc(sizeof(struct whiteheat_private), GFP_KERNEL);
-		if (info == NULL)
-			goto no_memory;
+		if (info == NULL) {
+			err("%s: Out of memory for port structures\n", serial->type->name);
+			goto no_private;
+		}
 
 		spin_lock_init(&info->lock);
 		info->flags = 0;
 		info->mcr = 0;
+		INIT_WORK(&info->rx_work, rx_data_softint, port);
+
+		INIT_LIST_HEAD(&info->rx_urbs_free);
+		INIT_LIST_HEAD(&info->rx_urbs_submitted);
+		INIT_LIST_HEAD(&info->rx_urb_q);
+		INIT_LIST_HEAD(&info->tx_urbs_free);
+		INIT_LIST_HEAD(&info->tx_urbs_submitted);
+
+		for (j = 0; j < urb_pool_size; j++) {
+			urb = usb_alloc_urb(0, GFP_KERNEL);
+			if (!urb) {
+				err("No free urbs available");
+				goto no_rx_urb;
+			}
+			buf_size = port->read_urb->transfer_buffer_length;
+			urb->transfer_buffer = kmalloc(buf_size, GFP_KERNEL);
+			if (!urb->transfer_buffer) {
+				err("Couldn't allocate urb buffer");
+				goto no_rx_buf;
+			}
+			wrap = kmalloc(sizeof(*wrap), GFP_KERNEL);
+			if (!wrap) {
+				err("Couldn't allocate urb wrapper");
+				goto no_rx_wrap;
+			}
+			usb_fill_bulk_urb(urb, serial->dev,
+					usb_rcvbulkpipe(serial->dev,
+						port->bulk_in_endpointAddress),
+					urb->transfer_buffer, buf_size,
+					whiteheat_read_callback, port);
+			wrap->urb = urb;
+			list_add(&wrap->list, &info->rx_urbs_free);
+
+			urb = usb_alloc_urb(0, GFP_KERNEL);
+			if (!urb) {
+				err("No free urbs available");
+				goto no_tx_urb;
+			}
+			buf_size = port->write_urb->transfer_buffer_length;
+			urb->transfer_buffer = kmalloc(buf_size, GFP_KERNEL);
+			if (!urb->transfer_buffer) {
+				err("Couldn't allocate urb buffer");
+				goto no_tx_buf;
+			}
+			wrap = kmalloc(sizeof(*wrap), GFP_KERNEL);
+			if (!wrap) {
+				err("Couldn't allocate urb wrapper");
+				goto no_tx_wrap;
+			}
+			usb_fill_bulk_urb(urb, serial->dev,
+					usb_sndbulkpipe(serial->dev,
+						port->bulk_out_endpointAddress),
+					urb->transfer_buffer, buf_size,
+					whiteheat_write_callback, port);
+			wrap->urb = urb;
+			list_add(&wrap->list, &info->tx_urbs_free);
+		}
+
 		port->private = info;
 	}
 
 	command_info = (struct whiteheat_command_private *)kmalloc(sizeof(struct whiteheat_command_private), GFP_KERNEL);
-	if (command_info == NULL)
-		goto no_memory;
+	if (command_info == NULL) {
+		err("%s: Out of memory for port structures\n", serial->type->name);
+		goto no_command_private;
+	}
 
 	spin_lock_init(&command_info->lock);
 	command_info->port_running = 0;
@@ -402,12 +487,35 @@ static int whiteheat_attach (struct usb_serial *serial)
 	err("%s: please contact support@connecttech.com\n", serial->type->name);
 	return -ENODEV;
 
-no_memory:
-	for (i--; i >= 0; i--) {
+no_command_private:
+	for (i = serial->num_ports - 1; i >= 0; i--) {
 		port = &serial->port[i];
-		kfree(port->private);
+		info = port->private;
+		for (j = urb_pool_size - 1; j >= 0; j--) {
+			tmp = list_first(&info->tx_urbs_free);
+			list_del(tmp);
+			wrap = list_entry(tmp, struct whiteheat_urb_wrap, list);
+			urb = wrap->urb;
+			kfree(wrap);
+no_tx_wrap:
+			kfree(urb->transfer_buffer);
+no_tx_buf:
+			usb_free_urb(urb);
+no_tx_urb:
+			tmp = list_first(&info->rx_urbs_free);
+			list_del(tmp);
+			wrap = list_entry(tmp, struct whiteheat_urb_wrap, list);
+			urb = wrap->urb;
+			kfree(wrap);
+no_rx_wrap:
+			kfree(urb->transfer_buffer);
+no_rx_buf:
+			usb_free_urb(urb);
+no_rx_urb:
+		}
+		kfree(info);
+no_private:
 	}
-	err("%s: Out of memory for port structures\n", serial->type->name);
 	return -ENOMEM;
 }
 
@@ -416,6 +524,11 @@ static void whiteheat_shutdown (struct usb_serial *serial)
 {
 	struct usb_serial_port *command_port;
 	struct usb_serial_port *port;
+	struct whiteheat_private *info;
+	struct whiteheat_urb_wrap *wrap;
+	struct urb *urb;
+	struct list_head *tmp;
+	struct list_head *tmp2;
 	int i;
 
 	dbg("%s", __FUNCTION__);
@@ -423,12 +536,27 @@ static void whiteheat_shutdown (struct usb_serial *serial)
 	/* free up our private data for our command port */
 	command_port = &serial->port[COMMAND_PORT];
 	kfree (command_port->private);
-	command_port->private = NULL;
 
 	for (i = 0; i < serial->num_ports; i++) {
 		port = &serial->port[i];
-		kfree(port->private);
-		port->private = NULL;
+		info = port->private;
+		list_for_each_safe(tmp, tmp2, &info->rx_urbs_free) {
+			list_del(tmp);
+			wrap = list_entry(tmp, struct whiteheat_urb_wrap, list);
+			urb = wrap->urb;
+			kfree(wrap);
+			kfree(urb->transfer_buffer);
+			usb_free_urb(urb);
+		}
+		list_for_each_safe(tmp, tmp2, &info->tx_urbs_free) {
+			list_del(tmp);
+			wrap = list_entry(tmp, struct whiteheat_urb_wrap, list);
+			urb = wrap->urb;
+			kfree(wrap);
+			kfree(urb->transfer_buffer);
+			usb_free_urb(urb);
+		}
+		kfree(info);
 	}
 
 	return;
@@ -446,6 +574,9 @@ static int whiteheat_open (struct usb_serial_port *port, struct file *filp)
 	if (retval)
 		goto exit;
 
+	if (port->tty)
+		port->tty->low_latency = 1;
+
 	/* send an open port command */
 	retval = firm_open(port);
 	if (retval) {
@@ -469,8 +600,7 @@ static int whiteheat_open (struct usb_serial_port *port, struct file *filp)
 	usb_clear_halt(port->serial->dev, port->write_urb->pipe);
 
 	/* Start reading from the device */
-	port->read_urb->dev = port->serial->dev;
-	retval = usb_submit_urb(port->read_urb, GFP_KERNEL);
+	retval = start_port_read(port);
 	if (retval) {
 		err("%s - failed submitting read urb, error %d", __FUNCTION__, retval);
 		firm_close(port);
@@ -486,6 +616,13 @@ static int whiteheat_open (struct usb_serial_port *port, struct file *filp)
 
 static void whiteheat_close(struct usb_serial_port *port, struct file * filp)
 {
+	struct whiteheat_private *info = port->private;
+	struct whiteheat_urb_wrap *wrap;
+	struct urb *urb;
+	struct list_head *tmp;
+	struct list_head *tmp2;
+	unsigned long flags;
+
 	dbg("%s - port %d", __FUNCTION__, port->number);
 	
 	/* filp is NULL when called from usb_serial_disconnect */
@@ -515,8 +652,26 @@ static void whiteheat_close(struct usb_serial_port *port, struct file * filp)
 	firm_close(port);
 
 	/* shutdown our bulk reads and writes */
-	usb_unlink_urb (port->write_urb);
-	usb_unlink_urb (port->read_urb);
+	spin_lock_irqsave(&info->lock, flags);
+	list_for_each_safe(tmp, tmp2, &info->rx_urbs_submitted) {
+		wrap = list_entry(tmp, struct whiteheat_urb_wrap, list);
+		urb = wrap->urb;
+		usb_unlink_urb(urb);
+		list_del(tmp);
+		list_add(tmp, &info->rx_urbs_free);
+	}
+	list_for_each_safe(tmp, tmp2, &info->rx_urb_q) {
+		list_del(tmp);
+		list_add(tmp, &info->rx_urbs_free);
+	}
+	list_for_each_safe(tmp, tmp2, &info->tx_urbs_submitted) {
+		wrap = list_entry(tmp, struct whiteheat_urb_wrap, list);
+		urb = wrap->urb;
+		usb_unlink_urb(urb);
+		list_del(tmp);
+		list_add(tmp, &info->tx_urbs_free);
+	}
+	spin_unlock_irqrestore(&info->lock, flags);
 
 	stop_command_port(port->serial);
 
@@ -527,7 +682,14 @@ static void whiteheat_close(struct usb_serial_port *port, struct file * filp)
 static int whiteheat_write(struct usb_serial_port *port, int from_user, const unsigned char *buf, int count)
 {
 	struct usb_serial *serial = port->serial;
+	struct whiteheat_private *info = port->private;
+	struct whiteheat_urb_wrap *wrap;
+	struct urb *urb;
 	int result;
+	int bytes;
+	int sent = 0;
+	unsigned long flags;
+	struct list_head *tmp;
 
 	dbg("%s - port %d", __FUNCTION__, port->number);
 
@@ -536,43 +698,65 @@ static int whiteheat_write(struct usb_serial_port *port, int from_user, const un
 		return (0);
 	}
 
-	if (port->write_urb->status == -EINPROGRESS) {
-		dbg ("%s - already writing", __FUNCTION__);
-		return (0);
+	while (count) {
+		spin_lock_irqsave(&info->lock, flags);
+		if (list_empty(&info->tx_urbs_free)) {
+			spin_unlock_irqrestore(&info->lock, flags);
+			break;
 		}
+		tmp = list_first(&info->tx_urbs_free);
+		list_del(tmp);
+		spin_unlock_irqrestore(&info->lock, flags);
 
-	count = (count > port->bulk_out_size) ? port->bulk_out_size : count;
-
+		wrap = list_entry(tmp, struct whiteheat_urb_wrap, list);
+		urb = wrap->urb;
+		bytes = (count > port->bulk_out_size) ? port->bulk_out_size : count;
 		if (from_user) {
-		if (copy_from_user(port->write_urb->transfer_buffer, buf, count))
+			if (copy_from_user(urb->transfer_buffer, buf + sent, bytes))
 				return -EFAULT;
-	}
-	else {
-		memcpy (port->write_urb->transfer_buffer, buf, count);
+		} else {
+			memcpy (urb->transfer_buffer, buf + sent, bytes);
 		}
 
-	usb_serial_debug_data (__FILE__, __FUNCTION__, count, port->write_urb->transfer_buffer);
+		usb_serial_debug_data (__FILE__, __FUNCTION__, bytes, urb->transfer_buffer);
 
-	port->write_urb->dev = serial->dev;
-	port->write_urb->transfer_buffer_length = count;
-	result = usb_submit_urb(port->write_urb, GFP_ATOMIC);
-	if (result)
+		urb->dev = serial->dev;
+		urb->transfer_buffer_length = bytes;
+		result = usb_submit_urb(urb, GFP_ATOMIC);
+		if (result) {
 			err("%s - failed submitting write urb, error %d", __FUNCTION__, result);
-	else
-		result = count;
+			sent = result;
+			spin_lock_irqsave(&info->lock, flags);
+			list_add(tmp, &info->tx_urbs_free);
+			spin_unlock_irqrestore(&info->lock, flags);
+			break;
+		} else {
+			sent += bytes;
+			count -= bytes;
+			spin_lock_irqsave(&info->lock, flags);
+			list_add(tmp, &info->tx_urbs_submitted);
+			spin_unlock_irqrestore(&info->lock, flags);
+		}
+	}
 
-	return result;
+	return sent;
 }
 
 
 static int whiteheat_write_room(struct usb_serial_port *port)
 {
+	struct whiteheat_private *info = port->private;
+	struct list_head *tmp;
 	int room = 0;
+	unsigned long flags;
 
 	dbg("%s - port %d", __FUNCTION__, port->number);
 	
-	if (port->write_urb->status != -EINPROGRESS)
-		room = port->bulk_out_size;
+	spin_lock_irqsave(&info->lock, flags);
+	list_for_each(tmp, &info->tx_urbs_free)
+		room++;
+	spin_unlock_irqrestore(&info->lock, flags);
+	room *= port->bulk_out_size;
 
 	dbg("%s - returns %d", __FUNCTION__, room);
 	return (room);
@@ -715,12 +899,20 @@ static void whiteheat_break_ctl(struct usb_serial_port *port, int break_state) {
 
 static int whiteheat_chars_in_buffer(struct usb_serial_port *port)
 {
+	struct whiteheat_private *info = port->private;
+	struct list_head *tmp;
+	struct whiteheat_urb_wrap *wrap;
 	int chars = 0;
+	unsigned long flags;
 
 	dbg("%s - port %d", __FUNCTION__, port->number);
 
-	if (port->write_urb->status == -EINPROGRESS)
-		chars = port->write_urb->transfer_buffer_length;
+	spin_lock_irqsave(&info->lock, flags);
+	list_for_each(tmp, &info->tx_urbs_submitted) {
+		wrap = list_entry(tmp, struct whiteheat_urb_wrap, list);
+		chars += wrap->urb->transfer_buffer_length;
+	}
+	spin_unlock_irqrestore(&info->lock, flags);
 
 	dbg ("%s - returns %d", __FUNCTION__, chars);
 	return (chars);
@@ -745,25 +937,19 @@ static void whiteheat_throttle (struct usb_serial_port *port)
 static void whiteheat_unthrottle (struct usb_serial_port *port)
 {
 	struct whiteheat_private *info = (struct whiteheat_private *)port->private;
-	int result;
+	int actually_throttled;
 	unsigned long flags;
 
 	dbg("%s - port %d", __FUNCTION__, port->number);
 
 	spin_lock_irqsave(&info->lock, flags);
-
-	if (info->flags & ACTUALLY_THROTTLED) {
-		/* Continue trying to always read  */
-		port->read_urb->dev = port->serial->dev;
-		result = usb_submit_urb(port->read_urb, GFP_ATOMIC);
-		if (result)
-			err("%s - failed resubmitting read urb, error %d", __FUNCTION__, result);
-	}
-
+	actually_throttled = info->flags & ACTUALLY_THROTTLED;
 	info->flags &= ~(THROTTLED | ACTUALLY_THROTTLED);
-
 	spin_unlock_irqrestore(&info->lock, flags);
 
+	if (actually_throttled)
+		rx_data_softint(port);
+
 	return;
 }
 
@@ -846,53 +1032,50 @@ static void whiteheat_read_callback(struct urb *urb)
 {
 	struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
 	struct usb_serial *serial = get_usb_serial (port, __FUNCTION__);
-	struct tty_struct *tty;
+	struct whiteheat_urb_wrap *wrap;
 	unsigned char *data = urb->transfer_buffer;
-	int i;
-	int result;
 	struct whiteheat_private *info = (struct whiteheat_private *)port->private;
-	unsigned long flags;
 
 	dbg("%s - port %d", __FUNCTION__, port->number);
 
+	spin_lock(&info->lock);
+	wrap = urb_to_wrap(urb, &info->rx_urbs_submitted);
+	if (!wrap) {
+		spin_unlock(&info->lock);
+		err("%s - Not my urb!", __FUNCTION__);
+		return;
+	}
+	list_del(&wrap->list);
+	spin_unlock(&info->lock);
+
 	if (!serial) {
 		dbg("%s - bad serial pointer, exiting", __FUNCTION__);
+		spin_lock(&info->lock);
+		list_add(&wrap->list, &info->rx_urbs_free);
+		spin_unlock(&info->lock);
 		return;
 	}
 
 	if (urb->status) {
 		dbg("%s - nonzero read bulk status received: %d", __FUNCTION__, urb->status);
+		spin_lock(&info->lock);
+		list_add(&wrap->list, &info->rx_urbs_free);
+		spin_unlock(&info->lock);
 		return;
 	}
 
 	usb_serial_debug_data (__FILE__, __FUNCTION__, urb->actual_length, data);
 
-	tty = port->tty;
-	if (tty && urb->actual_length) {
-		for (i = 0; i < urb->actual_length ; ++i) {
-			/* if we insert more than TTY_FLIPBUF_SIZE characters, we drop them. */
-			if(tty->flip.count >= TTY_FLIPBUF_SIZE) {
-				tty_flip_buffer_push(tty);
-			}
-			/* this doesn't actually push the data through unless tty->low_latency is set */
-			tty_insert_flip_char(tty, data[i], 0);
-		}
-	  	tty_flip_buffer_push(tty);
-	}
-
-	spin_lock_irqsave(&info->lock, flags);
+	spin_lock(&info->lock);
+	list_add_tail(&wrap->list, &info->rx_urb_q);
 	if (info->flags & THROTTLED) {
 		info->flags |= ACTUALLY_THROTTLED;
-		spin_unlock_irqrestore(&info->lock, flags);
+		spin_unlock(&info->lock);
 		return;
 	}
-	spin_unlock_irqrestore(&info->lock, flags);
+	spin_unlock(&info->lock);
 
-	/* Continue trying to always read  */
-	port->read_urb->dev = serial->dev;
-	result = usb_submit_urb(port->read_urb, GFP_ATOMIC);
-	if (result)
-		err("%s - failed resubmitting read urb, error %d", __FUNCTION__, result);
+	schedule_work(&info->rx_work);
 }
 
 
@@ -900,9 +1083,22 @@ static void whiteheat_write_callback(struct urb *urb)
 {
 	struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
 	struct usb_serial *serial = get_usb_serial (port, __FUNCTION__);
+	struct whiteheat_private *info = port->private;
+	struct whiteheat_urb_wrap *wrap;
 
 	dbg("%s - port %d", __FUNCTION__, port->number);
 
+	spin_lock(&info->lock);
+	wrap = urb_to_wrap(urb, &info->tx_urbs_submitted);
+	if (!wrap) {
+		spin_unlock(&info->lock);
+		err("%s - Not my urb!", __FUNCTION__);
+		return;
+	}
+	list_del(&wrap->list);
+	list_add(&wrap->list, &info->tx_urbs_free);
+	spin_unlock(&info->lock);
+
 	if (!serial) {
 		dbg("%s - bad serial pointer, exiting", __FUNCTION__);
 		return;
@@ -1176,6 +1372,122 @@ static void stop_command_port(struct usb_serial *serial)
 }
 
 
+static int start_port_read(struct usb_serial_port *port) {
+	struct whiteheat_private *info = port->private;
+	struct whiteheat_urb_wrap *wrap;
+	struct urb *urb;
+	int retval = 0;
+	unsigned long flags;
+	struct list_head *tmp;
+	struct list_head *tmp2;
+
+	spin_lock_irqsave(&info->lock, flags);
+
+	list_for_each_safe(tmp, tmp2, &info->rx_urbs_free) {
+		list_del(tmp);
+		wrap = list_entry(tmp, struct whiteheat_urb_wrap, list);
+		urb = wrap->urb;
+		urb->dev = port->serial->dev;
+		retval = usb_submit_urb(urb, GFP_KERNEL);
+		if (retval) {
+			list_add(tmp, &info->rx_urbs_free);
+			list_for_each_safe(tmp, tmp2, &info->rx_urbs_submitted) {
+				wrap = list_entry(tmp, struct whiteheat_urb_wrap, list);
+				urb = wrap->urb;
+				usb_unlink_urb(urb);
+				list_del(tmp);
+				list_add(tmp, &info->rx_urbs_free);
+			}
+			break;
+		}
+		list_add(tmp, &info->rx_urbs_submitted);
+	}
+
+	spin_unlock_irqrestore(&info->lock, flags);
+
+	return retval;
+}
+
+
+static struct whiteheat_urb_wrap *urb_to_wrap(struct urb* urb, struct list_head *head) {
+	struct whiteheat_urb_wrap *wrap;
+	struct list_head *tmp;
+
+	list_for_each(tmp, head) {
+		wrap = list_entry(tmp, struct whiteheat_urb_wrap, list);
+		if (wrap->urb == urb)
+			return wrap;
+	}
+
+	return NULL;
+}
+
+
+static struct list_head *list_first(struct list_head *head) {
+	return head->next;
+}
+
+
+static void rx_data_softint(void *private) {
+	struct usb_serial_port *port = (struct usb_serial_port *)private;
+	struct whiteheat_private *info = port->private;
+	struct tty_struct *tty = port->tty;
+	struct whiteheat_urb_wrap *wrap;
+	struct urb *urb;
+	unsigned long flags;
+	struct list_head *tmp;
+	struct list_head *tmp2;
+	int result;
+	int sent = 0;
+
+	spin_lock_irqsave(&info->lock, flags);
+	if (info->flags & THROTTLED) {
+		spin_unlock_irqrestore(&info->lock, flags);
+		return;
+	}
+
+	list_for_each_safe(tmp, tmp2, &info->rx_urb_q) {
+		list_del(tmp);
+		spin_unlock_irqrestore(&info->lock, flags);
+
+		wrap = list_entry(tmp, struct whiteheat_urb_wrap, list);
+		urb = wrap->urb;
+
+		if (tty && urb->actual_length) {
+			if (urb->actual_length > TTY_FLIPBUF_SIZE - tty->flip.count) {
+				spin_lock_irqsave(&info->lock, flags);
+				list_add(tmp, &info->rx_urb_q);
+				spin_unlock_irqrestore(&info->lock, flags);
+				tty_flip_buffer_push(tty);
+				schedule_work(&info->rx_work);
+				return;
+			}
+
+			memcpy(tty->flip.char_buf_ptr, urb->transfer_buffer, urb->actual_length);
+			tty->flip.char_buf_ptr += urb->actual_length;
+			tty->flip.count += urb->actual_length;
+			sent += urb->actual_length;
+		}
+
+		urb->dev = port->serial->dev;
+		result = usb_submit_urb(urb, GFP_ATOMIC);
+		if (result) {
+			err("%s - failed resubmitting read urb, error %d", __FUNCTION__, result);
+			spin_lock_irqsave(&info->lock, flags);
+			list_add(tmp, &info->rx_urbs_free);
+			continue;
+		}
+
+		spin_lock_irqsave(&info->lock, flags);
+		list_add(tmp, &info->rx_urbs_submitted);
+	}
+	spin_unlock_irqrestore(&info->lock, flags);
+
+	if (sent)
+		tty_flip_buffer_push(tty);
+}
+
+
 /*****************************************************************************
  * Connect Tech's White Heat module functions
  *****************************************************************************/
@@ -1204,5 +1516,8 @@ MODULE_AUTHOR( DRIVER_AUTHOR );
 MODULE_DESCRIPTION( DRIVER_DESC );
 MODULE_LICENSE("GPL");
 
+MODULE_PARM(urb_pool_size, "i");
+MODULE_PARM_DESC(urb_pool_size, "Number of urbs to use for buffering");
+
 MODULE_PARM(debug, "i");
 MODULE_PARM_DESC(debug, "Debug enabled or not");