staging: comedi: check data length for INSN_CONFIG_DIGITAL_TRIG

The newly defined format for the `INSN_CONFIG_DIGITAL_TRIG`
configuration instruction expects 6 data values.  Check the length in
`check_insn_config_length()` before calling the comedi subdevice's
`insn_config` handler.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedi_fops.c

@@ -880,6 +880,10 @@ static int check_insn_config_length(struct comedi_insn *insn,
 		if (insn->n == 5)
 			return 0;
 		break;
+	case INSN_CONFIG_DIGITAL_TRIG:
+		if (insn->n == 6)
+			return 0;
+		break;
 		/* by default we allow the insn since we don't have checks for
 		 * all possible cases yet */
 	default: