staging: comedi: usbdux: fix the cmd->start_arg use

For all cmd->start_src values this driver trivially validates that the
cmd->start_arg is 0.

For a TRIG_INT source, the cmd->start_arg is actually the valid trig_num
that is used by the async (*inttrig) callback.

Refactor the (*inttrig) functions so that the cmd->start_arg is used to
check the trig_num instead of the open coded values.
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/usbdux.c

@@ -692,15 +692,16 @@ static int receive_dux_commands(struct comedi_device *dev, unsigned int command)
 
 static int usbdux_ai_inttrig(struct comedi_device *dev,
 			     struct comedi_subdevice *s,
-			     unsigned int trignum)
+			     unsigned int trig_num)
 {
 	struct usbdux_private *devpriv = dev->private;
-	int ret = -EINVAL;
+	struct comedi_cmd *cmd = &s->async->cmd;
+	int ret;
 
-	down(&devpriv->sem);
+	if (trig_num != cmd->start_arg)
+		return -EINVAL;
 
-	if (trignum != 0)
-		goto ai_trig_exit;
+	down(&devpriv->sem);
 
 	if (!devpriv->ai_cmd_running) {
 		devpriv->ai_cmd_running = 1;
@@ -913,15 +914,16 @@ static int usbdux_ao_insn_write(struct comedi_device *dev,
 
 static int usbdux_ao_inttrig(struct comedi_device *dev,
 			     struct comedi_subdevice *s,
-			     unsigned int trignum)
+			     unsigned int trig_num)
 {
 	struct usbdux_private *devpriv = dev->private;
-	int ret = -EINVAL;
+	struct comedi_cmd *cmd = &s->async->cmd;
+	int ret;
 
-	down(&devpriv->sem);
+	if (trig_num != cmd->start_arg)
+		return -EINVAL;
 
-	if (trignum != 0)
-		goto ao_trig_exit;
+	down(&devpriv->sem);
 
 	if (!devpriv->ao_cmd_running) {
 		devpriv->ao_cmd_running = 1;