USB: cdc-wdm: support back-to-back USB_CDC_NOTIFY_RESPONSE_AVAILABLE notifications

Some MBIM devices send back-to-back USB_CDC_NOTIFY_RESPONSE_AVAILABLE notifications
when sending a message over multiple fragments or when there are unsolicited
messages available.

Count up the number of USB_CDC_NOTIFY_RESPONSE_AVAILABLE notifications received
and decrement the count and submit the urb for the next response each time userspace
completes a read the response.

Signed-off-by: Greg Suarez <gsuarez@smithmicro.com>
Acked-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index d3318a0..589ea58 100644 (file)
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -101,6 +101,7 @@ struct wdm_device {
        struct work_struct      rxwork;
        int                     werr;
        int                     rerr;
+       int                     resp_count;
 
        struct list_head        device_list;
        int                     (*manage_power)(struct usb_interface *, int);
@@ -262,9 +263,9 @@ static void wdm_int_callback(struct urb *urb)
        }
 
        spin_lock(&desc->iuspin);
-       clear_bit(WDM_READ, &desc->flags);
        responding = test_and_set_bit(WDM_RESPONDING, &desc->flags);
-       if (!responding && !test_bit(WDM_DISCONNECTING, &desc->flags)
+       if (!desc->resp_count++ && !responding
+               && !test_bit(WDM_DISCONNECTING, &desc->flags)
                && !test_bit(WDM_SUSPENDING, &desc->flags)) {
                rv = usb_submit_urb(desc->response, GFP_ATOMIC);
                dev_dbg(&desc->intf->dev, "%s: usb_submit_urb %d",
@@ -521,10 +522,36 @@ retry:
 
        desc->length -= cntr;
        /* in case we had outstanding data */
-       if (!desc->length)
+       if (!desc->length) {
                clear_bit(WDM_READ, &desc->flags);
 
-       spin_unlock_irq(&desc->iuspin);
+               if (--desc->resp_count) {
+                       set_bit(WDM_RESPONDING, &desc->flags);
+                       spin_unlock_irq(&desc->iuspin);
+
+                       rv = usb_submit_urb(desc->response, GFP_KERNEL);
+                       if (rv) {
+                               dev_err(&desc->intf->dev,
+                                       "%s: usb_submit_urb failed with result %d\n",
+                                       __func__, rv);
+                               spin_lock_irq(&desc->iuspin);
+                               clear_bit(WDM_RESPONDING, &desc->flags);
+                               spin_unlock_irq(&desc->iuspin);
+
+                               if (rv == -ENOMEM) {
+                                       rv = schedule_work(&desc->rxwork);
+                                       if (rv)
+                                               dev_err(&desc->intf->dev, "Cannot schedule work\n");
+                               } else {
+                                       spin_lock_irq(&desc->iuspin);
+                                       desc->resp_count = 0;
+                                       spin_unlock_irq(&desc->iuspin);
+                               }
+                       }
+               } else
+                       spin_unlock_irq(&desc->iuspin);
+       } else
+               spin_unlock_irq(&desc->iuspin);
 
        rv = cntr;
 
@@ -635,6 +662,9 @@ static int wdm_release(struct inode *inode, struct file *file)
                if (!test_bit(WDM_DISCONNECTING, &desc->flags)) {
                        dev_dbg(&desc->intf->dev, "wdm_release: cleanup");
                        kill_urbs(desc);
+                       spin_lock_irq(&desc->iuspin);
+                       desc->resp_count = 0;
+                       spin_unlock_irq(&desc->iuspin);
                        desc->manage_power(desc->intf, 0);
                } else {
                        /* must avoid dev_printk here as desc->intf is invalid */