staging: comedi: usbduxfast: introduce usbduxfast_ai_handle_urb()

Factor the urb handling and resubmit out of the completion handler and
tidy it up. This allows a common exit path to be used in the completion
handler to stop the async command and handle the events.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: Bernd Porr <mail@berndporr.me.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/usbduxfast.c

@@ -236,114 +236,87 @@ static int usbduxfast_ai_cancel(struct comedi_device *dev,
 	return ret;
 }
 
-/*
- * analogue IN
- * interrupt service routine
- */
+static void usbduxfast_ai_handle_urb(struct comedi_device *dev,
+				     struct comedi_subdevice *s,
+				     struct urb *urb)
+{
+	struct usbduxfast_private *devpriv = dev->private;
+	struct comedi_async *async = s->async;
+	struct comedi_cmd *cmd = &async->cmd;
+	int ret;
+
+	if (devpriv->ignore) {
+		devpriv->ignore--;
+	} else {
+		unsigned int nbytes = urb->actual_length;
+
+		if (cmd->stop_src == TRIG_COUNT) {
+			unsigned int nsamples = nbytes / bytes_per_sample(s);
+
+			if (devpriv->ai_sample_count < nsamples) {
+				nsamples = devpriv->ai_sample_count;
+				async->events |= COMEDI_CB_EOA;
+			}
+			devpriv->ai_sample_count -= nsamples;
+			nbytes = nsamples * bytes_per_sample(s);
+		}
+
+		cfc_write_array_to_buffer(s, urb->transfer_buffer, nbytes);
+	}
+
+	/* if command is still running, resubmit urb for BULK transfer */
+	if (!(async->events & COMEDI_CB_CANCEL_MASK)) {
+		urb->dev = comedi_to_usb_dev(dev);
+		urb->status = 0;
+		ret = usb_submit_urb(urb, GFP_ATOMIC);
+		if (ret < 0) {
+			dev_err(dev->class_dev, "urb resubm failed: %d", ret);
+			async->events |= COMEDI_CB_ERROR;
+		}
+	}
+}
+
 static void usbduxfast_ai_interrupt(struct urb *urb)
 {
 	struct comedi_device *dev = urb->context;
 	struct comedi_subdevice *s = dev->read_subdev;
 	struct comedi_async *async = s->async;
-	struct comedi_cmd *cmd = &async->cmd;
-	struct usb_device *usb = comedi_to_usb_dev(dev);
 	struct usbduxfast_private *devpriv = dev->private;
-	int n, err;
 
-	/* are we running a command? */
-	if (unlikely(!devpriv->ai_cmd_running)) {
-		/*
-		 * not running a command
-		 * do not continue execution if no asynchronous command
-		 * is running in particular not resubmit
-		 */
+	/* exit if not running a command, do not resubmit urb */
+	if (!devpriv->ai_cmd_running)
 		return;
-	}
 
-	/* first we test if something unusual has just happened */
 	switch (urb->status) {
 	case 0:
+		usbduxfast_ai_handle_urb(dev, s, urb);
 		break;
 
-		/*
-		 * happens after an unlink command or when the device
-		 * is plugged out
-		 */
 	case -ECONNRESET:
 	case -ENOENT:
 	case -ESHUTDOWN:
 	case -ECONNABORTED:
-		/* tell this comedi */
-		async->events |= COMEDI_CB_EOA;
+		/* after an unlink command, unplug, ... etc */
 		async->events |= COMEDI_CB_ERROR;
-		comedi_event(dev, s);
-		/* stop the transfer w/o unlink */
-		usbduxfast_ai_stop(dev, 0);
-		return;
+		break;
 
 	default:
+		/* a real error */
 		dev_err(dev->class_dev,
 			"non-zero urb status received in ai intr context: %d\n",
 			urb->status);
-		async->events |= COMEDI_CB_EOA;
 		async->events |= COMEDI_CB_ERROR;
-		comedi_event(dev, s);
-		usbduxfast_ai_stop(dev, 0);
-		return;
-	}
-
-	if (!devpriv->ignore) {
-		if (cmd->stop_src == TRIG_COUNT) {
-			/* not continuous, fixed number of samples */
-			n = urb->actual_length / sizeof(uint16_t);
-			if (unlikely(devpriv->ai_sample_count < n)) {
-				unsigned int num_bytes;
-
-				/* partial sample received */
-				num_bytes = devpriv->ai_sample_count *
-					    sizeof(uint16_t);
-				cfc_write_array_to_buffer(s,
-							  urb->transfer_buffer,
-							  num_bytes);
-				usbduxfast_ai_stop(dev, 0);
-				/* tell comedi that the acquistion is over */
-				async->events |= COMEDI_CB_EOA;
-				comedi_event(dev, s);
-				return;
-			}
-			devpriv->ai_sample_count -= n;
-		}
-		/* write the full buffer to comedi */
-		err = cfc_write_array_to_buffer(s, urb->transfer_buffer,
-						urb->actual_length);
-		if (unlikely(err == 0)) {
-			/* buffer overflow */
-			usbduxfast_ai_stop(dev, 0);
-			return;
-		}
-
-		/* tell comedi that data is there */
-		comedi_event(dev, s);
-	} else {
-		/* ignore this packet */
-		devpriv->ignore--;
+		break;
 	}
 
 	/*
-	 * command is still running
-	 * resubmit urb for BULK transfer
+	 * comedi_handle_events() cannot be used in this driver. The (*cancel)
+	 * operation would unlink the urb.
 	 */
-	urb->dev = usb;
-	urb->status = 0;
-	err = usb_submit_urb(urb, GFP_ATOMIC);
-	if (err < 0) {
-		dev_err(dev->class_dev,
-			"urb resubm failed: %d", err);
-		async->events |= COMEDI_CB_EOA;
-		async->events |= COMEDI_CB_ERROR;
-		comedi_event(dev, s);
+	if (async->events & COMEDI_CB_CANCEL_MASK)
 		usbduxfast_ai_stop(dev, 0);
-	}
+
+	comedi_event(dev, s);
 }
 
 static int usbduxfast_submit_urb(struct comedi_device *dev)