staging: comedi: pcmmio: remove "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/pcmmio.c

@@ -415,13 +415,6 @@ static int pcmmio_start_intr(struct comedi_device *dev,
 	unsigned int pol_bits = 0;
 	int i;
 
-	if (cmd->stop_src == TRIG_COUNT && devpriv->stop_count == 0) {
-		/* An empty acquisition! */
-		s->async->events |= COMEDI_CB_EOA;
-		devpriv->active = 0;
-		return 1;
-	}
-
 	devpriv->enabled_mask = 0;
 	devpriv->active = 1;
 	if (cmd->chanlist) {
@@ -549,16 +542,10 @@ static int pcmmio_cmdtest(struct comedi_device *dev,
 	err |= cfc_check_trigger_arg_is(&cmd->convert_arg, 0);
 	err |= cfc_check_trigger_arg_is(&cmd->scan_end_arg, cmd->chanlist_len);
 
-	switch (cmd->stop_src) {
-	case TRIG_COUNT:
-		/* any count allowed */
-		break;
-	case 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);
-		break;
-	default:
-		break;
-	}
 
 	if (err)
 		return 3;