staging: comedi: das16: introduce das16_ao_range()

Clarify the (*attach) a bit by introducing a helper function to handle the
setup of the analog output 'range_table'.

Some of the boards supported by this driver do not have programmable ranges.
The analog output subdevice can use optional range information provided by
the user during the attach of the driver. Currently this range data is
allocated and stored in the private data.

Use the subdevice private data member instead and allocate the memory with
comedi_alloc_spriv(). The comedi core will automatically free this memory
when the driver is detached. If the allocation fails set the 'range_table'
to 'range_unknown' instead of failing the driver attach.
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

@@ -443,7 +443,6 @@ struct das16_private_struct {
 	unsigned long		adc_byte_count;
 	unsigned int		divisor1;
 	unsigned int		divisor2;
-	struct comedi_lrange	*user_ao_range_table;
 	struct timer_list	timer;
 	short			timer_running;
 	unsigned long		extra_iobase;
@@ -987,13 +986,42 @@ static const struct comedi_lrange *das16_ai_range(struct comedi_device *dev,
 	return das16_ai_bip_lranges[pg_type];
 }
 
+static const struct comedi_lrange *das16_ao_range(struct comedi_device *dev,
+						  struct comedi_subdevice *s,
+						  struct comedi_devconfig *it)
+{
+	unsigned int min = it->options[6];
+	unsigned int max = it->options[7];
+
+	/* get any user-defined output range */
+	if (min || max) {
+		struct comedi_lrange *lrange;
+		struct comedi_krange *krange;
+
+		/* allocate single-range range table */
+		lrange = comedi_alloc_spriv(s,
+					    sizeof(*lrange) + sizeof(*krange));
+		if (!lrange)
+			return &range_unknown;
+
+		/* initialize ao range */
+		lrange->length = 1;
+		krange = lrange->range;
+		krange->min = min;
+		krange->max = max;
+		krange->flags = UNIT_volt;
+
+		return lrange;
+	}
+
+	return &range_unknown;
+}
+
 static int das16_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 {
 	const struct das16_board *board = dev->board_ptr;
 	struct das16_private_struct *devpriv;
 	struct comedi_subdevice *s;
-	struct comedi_lrange *lrange;
-	struct comedi_krange *krange;
 	unsigned int status;
 	int ret;
 
@@ -1050,22 +1078,6 @@ static int das16_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 
 	das16_alloc_dma(dev, it->options[2]);
 
-	/* get any user-defined output range */
-	if (it->options[6] || it->options[7]) {
-		/* allocate single-range range table */
-		lrange = kzalloc(sizeof(*lrange) + sizeof(*krange), GFP_KERNEL);
-		if (!lrange)
-			return -ENOMEM;
-
-		/* initialize ao range */
-		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);
 	if (ret)
 		return ret;
@@ -1103,7 +1115,7 @@ static int das16_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 		s->subdev_flags	= SDF_WRITABLE;
 		s->n_chan	= 2;
 		s->maxdata	= 0x0fff;
-		s->range_table	= devpriv->user_ao_range_table;
+		s->range_table	= das16_ao_range(dev, s, it);
 		s->insn_write	= das16_ao_insn_write;
 
 		ret = comedi_alloc_subdev_readback(s);
@@ -1165,7 +1177,6 @@ static void das16_detach(struct comedi_device *dev)
 		if (dev->iobase)
 			das16_reset(dev);
 		das16_free_dma(dev);
-		kfree(devpriv->user_ao_range_table);
 
 		if (devpriv->extra_iobase)
 			release_region(devpriv->extra_iobase,