staging: comedi: das16: tidy up user ai/ao range initialization

The allocation of the user range tables could fail. Make sure to check
for it.

Change the kmalloc()'s to kzalloc()'s to make sure the allocated range
tables are initialized to a known state.

Change the local variables so they can be used for both the ai and ao
range initialization and use shorter names to keep the lines < 80 chars.
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/das16.c

@@ -987,8 +987,8 @@ static int das16_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 	const struct das16_board *board = comedi_board(dev);
 	struct das16_private_struct *devpriv;
 	struct comedi_subdevice *s;
-	struct comedi_krange *user_ai_range;
-	struct comedi_krange *user_ao_range;
+	struct comedi_lrange *lrange;
+	struct comedi_krange *krange;
 	unsigned int dma_chan = it->options[2];
 	unsigned int status;
 	int ret;
@@ -1081,28 +1081,33 @@ static int das16_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 	if (board->ai_pg == das16_pg_none &&
 	    (it->options[4] || it->options[5])) {
 		/* allocate single-range range table */
-		devpriv->user_ai_range_table =
-		    kmalloc(sizeof(struct comedi_lrange) +
-			    sizeof(struct comedi_krange), GFP_KERNEL);
+		lrange = kzalloc(sizeof(*lrange) + sizeof(*krange), GFP_KERNEL);
+		if (!lrange)
+			return -ENOMEM;
+
 		/* initialize ai range */
-		devpriv->user_ai_range_table->length = 1;
-		user_ai_range = devpriv->user_ai_range_table->range;
-		user_ai_range->min = it->options[4];
-		user_ai_range->max = it->options[5];
-		user_ai_range->flags = UNIT_volt;
+		devpriv->user_ai_range_table = lrange;
+		lrange->length = 1;
+		krange = devpriv->user_ai_range_table->range;
+		krange->min = it->options[4];
+		krange->max = it->options[5];
+		krange->flags = UNIT_volt;
 	}
+
 	/* get any user-defined output range */
 	if (it->options[6] || it->options[7]) {
 		/* allocate single-range range table */
-		devpriv->user_ao_range_table =
-		    kmalloc(sizeof(struct comedi_lrange) +
-			    sizeof(struct comedi_krange), GFP_KERNEL);
+		lrange = kzalloc(sizeof(*lrange) + sizeof(*krange), GFP_KERNEL);
+		if (!lrange)
+			return -ENOMEM;
+
 		/* initialize ao range */
-		devpriv->user_ao_range_table->length = 1;
-		user_ao_range = devpriv->user_ao_range_table->range;
-		user_ao_range->min = it->options[6];
-		user_ao_range->max = it->options[7];
-		user_ao_range->flags = UNIT_volt;
+		devpriv->user_ao_range_table = lrange;
+		lrange->length = 1;
+		krange = devpriv->user_ao_range_table->range;
+		krange->min = it->options[6];
+		krange->max = it->options[7];
+		krange->flags = UNIT_volt;
 	}
 
 	ret = comedi_alloc_subdevices(dev, 4 + board->has_8255);