USB: cdc-acm: work around some broken devices

This patch introduces a work around for cdc-acm devices which are
low speed contrary to the specification, which requires bulk endpoints
which are banned in low speed and converted by usbcore to virtual
interrupt endpoints if they are used nevertheless.
Signed-off-by: Arseniy Lartsev <ars3n@yandex.ru>
Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/class/cdc-acm.c

@@ -387,6 +387,7 @@ static void acm_rx_tasklet(unsigned long _acm)
 	struct acm_ru *rcv;
 	unsigned long flags;
 	unsigned char throttled;
+	struct usb_host_endpoint *ep;
 
 	dbg("Entering acm_rx_tasklet");
 
@@ -462,6 +463,15 @@ static void acm_rx_tasklet(unsigned long _acm)
 
 		rcv->buffer = buf;
 
+		ep = (usb_pipein(acm->rx_endpoint) ? acm->dev->ep_in : acm->dev->ep_out)
+				[usb_pipeendpoint(acm->rx_endpoint)];
+		if (usb_endpoint_xfer_int(&ep->desc))
+			usb_fill_int_urb(rcv->urb, acm->dev,
+					 acm->rx_endpoint,
+					 buf->base,
+					 acm->readsize,
+					 acm_read_bulk, rcv, ep->desc.bInterval);
+		else
 			usb_fill_bulk_urb(rcv->urb, acm->dev,
 					  acm->rx_endpoint,
 					  buf->base,
@@ -1227,6 +1237,11 @@ static int acm_probe(struct usb_interface *intf,
 			goto alloc_fail7;
 		}
 
+		if (usb_endpoint_xfer_int(epwrite))
+			usb_fill_int_urb(snd->urb, usb_dev,
+				usb_sndbulkpipe(usb_dev, epwrite->bEndpointAddress),
+				NULL, acm->writesize, acm_write_bulk, snd, epwrite->bInterval);
+		else
 			usb_fill_bulk_urb(snd->urb, usb_dev,
 				usb_sndbulkpipe(usb_dev, epwrite->bEndpointAddress),
 				NULL, acm->writesize, acm_write_bulk, snd);