staging: comedi: amplc_pci230: remove analog output "empty acquisition" async command

This driver currently allows a cmd->stop_src == TRIG_COUNT with a cmd->stop_arg
of 0. This causes the (*do_cmd) to immediately generate a COMEDI_CB_EOA event
without acquiring any data.

This "empty acquisition" async command is not really useful. Validate that the
cmd->stop_arg is >= 1 in the (*do_cmdtest) and remove the "empty acquisition"
code.
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/amplc_pci230.c

@@ -987,7 +987,9 @@ static int pci230_ao_cmdtest(struct comedi_device *dev,
 
 	err |= cfc_check_trigger_arg_is(&cmd->scan_end_arg, cmd->chanlist_len);
 
-	if (cmd->stop_src == TRIG_NONE)
+	if (cmd->stop_src == TRIG_COUNT)
+		err |= cfc_check_trigger_arg_min(&cmd->stop_arg, 1);
+	else	/* TRIG_NONE */
 		err |= cfc_check_trigger_arg_is(&cmd->stop_arg, 0);
 
 	if (err)
@@ -1255,13 +1257,7 @@ static void pci230_ao_start(struct comedi_device *dev,
 	unsigned long irqflags;
 
 	devpriv->ao_cmd_started = true;
-	if (cmd->stop_src == TRIG_COUNT && devpriv->ao_scan_count == 0) {
-		/* An empty acquisition! */
-		async->events |= COMEDI_CB_EOA;
-		pci230_ao_stop(dev, s);
-		comedi_event(dev, s);
-		return;
-	}
+
 	if (devpriv->hwver >= 2) {
 		/* Using DAC FIFO. */
 		unsigned short scantrig;