staging: comedi: usbduxfast: TRIG_EXT only works for 1 or 16 channels

Move this check from the (*do_cmd) to the (*do_cmdtest).
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/usbduxfast.c

@@ -399,6 +399,11 @@ static int usbduxfast_ai_cmdtest(struct comedi_device *dev,
 	if (!cmd->chanlist_len)
 		err |= -EINVAL;
 
+	/* external start trigger is only valid for 1 or 16 channels */
+	if (cmd->start_src == TRIG_EXT &&
+	    cmd->chanlist_len != 1 && cmd->chanlist_len != 16)
+		err |= -EINVAL;
+
 	err |= comedi_check_trigger_arg_is(&cmd->scan_end_arg,
 					   cmd->chanlist_len);
 
@@ -519,13 +524,6 @@ static int usbduxfast_ai_cmd(struct comedi_device *dev,
 		up(&devpriv->sem);
 		return -EINVAL;
 	}
-	if ((cmd->start_src == TRIG_EXT) && (cmd->chanlist_len != 1)
-	    && (cmd->chanlist_len != 16)) {
-		dev_err(dev->class_dev,
-			"TRIG_EXT only with 1 or 16 channels possible\n");
-		up(&devpriv->sem);
-		return -EINVAL;
-	}
 
 	switch (cmd->chanlist_len) {
 	case 1: