staging: comedi: usbduxsigma: use comedi_buf_read_samples()

Use comedi_buf_read_samples() to read the analog output samples from
the async buffer. That function will set the COMEDI_CB_BLOCK event
when samples are read from the async buffer.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/usbduxsigma.c

@@ -374,7 +374,7 @@ static void usbduxsigma_ao_handle_urb(struct comedi_device *dev,
 			unsigned int chan = CR_CHAN(cmd->chanlist[i]);
 			unsigned short val;
 
-			if (!comedi_buf_get(s, &val)) {
+			if (!comedi_buf_read_samples(s, &val, 1)) {
 				dev_err(dev->class_dev, "buffer underflow\n");
 				async->events |= COMEDI_CB_OVERFLOW;
 				return;
@@ -384,7 +384,6 @@ static void usbduxsigma_ao_handle_urb(struct comedi_device *dev,
 			*datap++ = chan;
 			s->readback[chan] = val;
 		}
-		async->events |= COMEDI_CB_BLOCK;
 	}
 
 	/* if command is still running, resubmit urb */