staging: comedi: hwdrv_apci3200: properly validata the ai cmd->start_arg

The async command 'arguments' should be trivially validated in Step 3 of
the (*do_cmdtest) not Step 2b. Move the validataion in this driver to the
proper place.

This driver supports two cmd->start_src values, TRIG_NOW and TRIG_EXT.
TRIG_NOW sources should always have an arg of 0. The arg for TRIG_EXT
sources is driver specific.

Properly validate the cmd->start_arg based on the cmd->start_src. Remove
the noise when the arg is invalid and modify the cmd->start_arg so that
a valid value is returned to the user.
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/addi-data/hwdrv_apci3200.c

@@ -2221,12 +2221,11 @@ static int apci3200_ai_cmdtest(struct comedi_device *dev,
 	unsigned int ui_ConvertTimeBase = 0;
 	unsigned int ui_DelayTime = 0;
 	unsigned int ui_DelayTimeBase = 0;
-	int i_Triggermode = 0;
-	int i_TriggerEdge = 0;
 	int i_NbrOfChannel = 0;
 	int i_Cpt = 0;
 	double d_ConversionTimeForAllChannels = 0.0;
 	double d_SCANTimeNewUnit = 0.0;
+	unsigned int arg;
 
 	/* Step 1 : check if triggers are trivially valid */
 
@@ -2253,19 +2252,6 @@ static int apci3200_ai_cmdtest(struct comedi_device *dev,
 
 	/* Step 2b : and mutually compatible */
 
-	if (cmd->start_src == TRIG_EXT) {
-		i_TriggerEdge = cmd->start_arg & 0xFFFF;
-		i_Triggermode = cmd->start_arg >> 16;
-		if (i_TriggerEdge < 1 || i_TriggerEdge > 3) {
-			err++;
-			printk("\nThe trigger edge selection is in error\n");
-		}
-		if (i_Triggermode != 2) {
-			err++;
-			printk("\nThe trigger mode selection is in error\n");
-		}
-	}
-
 	if (err) {
 		apci3200_reset(dev);
 		return 2;
@@ -2273,6 +2259,28 @@ static int apci3200_ai_cmdtest(struct comedi_device *dev,
 
 	/* Step 3: check if arguments are trivially valid */
 
+	switch (cmd->start_src) {
+	case TRIG_NOW:
+		err |= cfc_check_trigger_arg_is(&cmd->start_arg, 0);
+		break;
+	case TRIG_EXT:
+		/* validate the trigger edge selection */
+		arg = cmd->start_arg & 0xffff;
+		if (arg < 1 || arg > 3) {
+			cmd->start_arg &= ~0xffff;
+			cmd->start_arg |= 1;
+			err |= -EINVAL;
+		}
+		/* validate the trigger mode selection */
+		arg = cmd->start_arg >> 16;
+		if (arg != 2) {
+			cmd->start_arg &= ~(0xffff << 16);
+			cmd->start_arg |= (2 << 16);
+			err |= -EINVAL;
+		}
+		break;
+	}
+
 	err |= cfc_check_trigger_arg_is(&cmd->scan_end_arg, cmd->chanlist_len);
 
 	/* i_FirstChannel=cmd->chanlist[0]; */