1 files changed, 84 insertions, 18 deletions

diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index 601e0648dec6..53baeec8f265 100644
--- a/drivers/usb/serial/generic.c
+++ b/drivers/usb/serial/generic.c
@@ -66,6 +66,8 @@ struct usb_serial_driver usb_serial_generic_device = {
         .num_bulk_out =         NUM_DONT_CARE,
         .num_ports =            1,
         .shutdown =             usb_serial_generic_shutdown,
+        .throttle =             usb_serial_generic_throttle,
+        .unthrottle =           usb_serial_generic_unthrottle,
 };
 
 static int generic_probe(struct usb_interface *interface,
@@ -115,6 +117,7 @@ int usb_serial_generic_open (struct usb_serial_port *port, struct file *filp)
 {
         struct usb_serial *serial = port->serial;
         int result = 0;
+        unsigned long flags;
 
         dbg("%s - port %d", __FUNCTION__, port->number);
 
@@ -124,7 +127,13 @@ int usb_serial_generic_open (struct usb_serial_port *port, struct file *filp)
         if (port->tty)
                 port->tty->low_latency = 1;
 
-        /* if we have a bulk interrupt, start reading from it */
+        /* clear the throttle flags */
+        spin_lock_irqsave(&port->lock, flags);
+        port->throttled = 0;
+        port->throttle_req = 0;
+        spin_unlock_irqrestore(&port->lock, flags);
+
+        /* if we have a bulk endpoint, start reading from it */
         if (serial->num_bulk_in) {
                 /* Start reading from the device */
                 usb_fill_bulk_urb (port->read_urb, serial->dev,
@@ -253,31 +262,22 @@ int usb_serial_generic_chars_in_buffer (struct usb_serial_port *port)
         return (chars);
 }
 
-void usb_serial_generic_read_bulk_callback (struct urb *urb)
+/* Push data to tty layer and resubmit the bulk read URB */
+static void flush_and_resubmit_read_urb (struct usb_serial_port *port)
 {
-        struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
         struct usb_serial *serial = port->serial;
-        struct tty_struct *tty;
-        unsigned char *data = urb->transfer_buffer;
+        struct urb *urb = port->read_urb;
+        struct tty_struct *tty = port->tty;
         int result;
 
-        dbg("%s - port %d", __FUNCTION__, port->number);
-
-        if (urb->status) {
-                dbg("%s - nonzero read bulk status received: %d", __FUNCTION__, urb->status);
-                return;
-        }
-
-        usb_serial_debug_data(debug, &port->dev, __FUNCTION__, urb->actual_length, data);
-
-        tty = port->tty;
+        /* Push data to tty */
         if (tty && urb->actual_length) {
                 tty_buffer_request_room(tty, urb->actual_length);
-                tty_insert_flip_string(tty, data, urb->actual_length);
-                tty_flip_buffer_push(tty);
+                tty_insert_flip_string(tty, urb->transfer_buffer, urb->actual_length);
+                tty_flip_buffer_push(tty); /* is this allowed from an URB callback ? */
         }
 
-        /* Continue trying to always read  */
+        /* Continue reading from device */
         usb_fill_bulk_urb (port->read_urb, serial->dev,
                            usb_rcvbulkpipe (serial->dev,
                                             port->bulk_in_endpointAddress),
@@ -290,6 +290,40 @@ void usb_serial_generic_read_bulk_callback (struct urb *urb)
         if (result)
                 dev_err(&port->dev, "%s - failed resubmitting read urb, error %d\n", __FUNCTION__, result);
 }
+
+void usb_serial_generic_read_bulk_callback (struct urb *urb)
+{
+        struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
+        unsigned char *data = urb->transfer_buffer;
+        int is_throttled;
+        unsigned long flags;
+
+        dbg("%s - port %d", __FUNCTION__, port->number);
+
+        if (urb->status) {
+                dbg("%s - nonzero read bulk status received: %d", __FUNCTION__, urb->status);
+                return;
+        }
+
+        usb_serial_debug_data(debug, &port->dev, __FUNCTION__, urb->actual_length, data);
+
+        /* Throttle the device if requested by tty */
+        if (urb->actual_length) {
+                spin_lock_irqsave(&port->lock, flags);
+                is_throttled = port->throttled = port->throttle_req;
+                spin_unlock_irqrestore(&port->lock, flags);
+                if (is_throttled) {
+                        /* Let the received data linger in the read URB;
+                         * usb_serial_generic_unthrottle() will pick it
+                         * up later. */
+                        dbg("%s - throttling device", __FUNCTION__);
+                        return;
+                }
+        }
+
+        /* Handle data and continue reading from device */
+        flush_and_resubmit_read_urb(port);
+}
 EXPORT_SYMBOL_GPL(usb_serial_generic_read_bulk_callback);
 
 void usb_serial_generic_write_bulk_callback (struct urb *urb)
@@ -308,6 +342,38 @@ void usb_serial_generic_write_bulk_callback (struct urb *urb)
 }
 EXPORT_SYMBOL_GPL(usb_serial_generic_write_bulk_callback);
 
+void usb_serial_generic_throttle (struct usb_serial_port *port)
+{
+        unsigned long flags;
+
+        dbg("%s - port %d", __FUNCTION__, port->number);
+
+        /* Set the throttle request flag. It will be picked up
+         * by usb_serial_generic_read_bulk_callback(). */
+        spin_lock_irqsave(&port->lock, flags);
+        port->throttle_req = 1;
+        spin_unlock_irqrestore(&port->lock, flags);
+}
+
+void usb_serial_generic_unthrottle (struct usb_serial_port *port)
+{
+        int was_throttled;
+        unsigned long flags;
+
+        dbg("%s - port %d", __FUNCTION__, port->number);
+
+        /* Clear the throttle flags */
+        spin_lock_irqsave(&port->lock, flags);
+        was_throttled = port->throttled;
+        port->throttled = port->throttle_req = 0;
+        spin_unlock_irqrestore(&port->lock, flags);
+
+        if (was_throttled) {
+                /* Handle pending data and resume reading from device */
+                flush_and_resubmit_read_urb(port);
+        }
+}
+
 void usb_serial_generic_shutdown (struct usb_serial *serial)
 {
         int i;