staging: comedi: cb_pcidas: tidy up analog output subdevice init

For aesthetics, add some whitespace to the subdevice initialization
and rename the (*insn_write) functions to follow the normal form
in comedi drivers.

It's not possible to actually read the analog outpus. For convienence
the subdevice readback provided by the core is used to return the
last value written to the subdevice. Remove the SDF_READABLE flag
from the subdev_flags.

Async command support uses interrupts. For clarity, make sure the
driver has an IRQ before initializing command support.
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/cb_pcidas.c

@@ -408,10 +408,10 @@ static int ai_config_insn(struct comedi_device *dev, struct comedi_subdevice *s,
 }
 
 /* analog output insn for pcidas-1000 and 1200 series */
-static int cb_pcidas_ao_nofifo_winsn(struct comedi_device *dev,
-				     struct comedi_subdevice *s,
-				     struct comedi_insn *insn,
-				     unsigned int *data)
+static int cb_pcidas_ao_nofifo_insn_write(struct comedi_device *dev,
+					  struct comedi_subdevice *s,
+					  struct comedi_insn *insn,
+					  unsigned int *data)
 {
 	struct cb_pcidas_private *devpriv = dev->private;
 	unsigned int chan = CR_CHAN(insn->chanspec);
@@ -436,9 +436,10 @@ static int cb_pcidas_ao_nofifo_winsn(struct comedi_device *dev,
 }
 
 /* analog output insn for pcidas-1602 series */
-static int cb_pcidas_ao_fifo_winsn(struct comedi_device *dev,
-				   struct comedi_subdevice *s,
-				   struct comedi_insn *insn, unsigned int *data)
+static int cb_pcidas_ao_fifo_insn_write(struct comedi_device *dev,
+					struct comedi_subdevice *s,
+					struct comedi_insn *insn,
+					unsigned int *data)
 {
 	struct cb_pcidas_private *devpriv = dev->private;
 	unsigned int chan = CR_CHAN(insn->chanspec);
@@ -1319,32 +1320,31 @@ static int cb_pcidas_auto_attach(struct comedi_device *dev,
 	s->do_cmdtest = cb_pcidas_ai_cmdtest;
 	s->cancel = cb_pcidas_cancel;
 
-	/* analog output subdevice */
+	/* Analog Output subdevice */
 	s = &dev->subdevices[1];
 	if (board->has_ao) {
-		s->type = COMEDI_SUBD_AO;
-		s->subdev_flags = SDF_READABLE | SDF_WRITABLE | SDF_GROUND;
-		s->n_chan = 2;
-		s->maxdata = board->is_16bit ? 0xffff : 0x0fff;
-		s->range_table = &cb_pcidas_ao_ranges;
-		/* default to no fifo (*insn_write) */
-		s->insn_write = cb_pcidas_ao_nofifo_winsn;
+		s->type		= COMEDI_SUBD_AO;
+		s->subdev_flags	= SDF_WRITABLE | SDF_GROUND;
+		s->n_chan	= 2;
+		s->maxdata	= board->is_16bit ? 0xffff : 0x0fff;
+		s->range_table	= &cb_pcidas_ao_ranges;
+		s->insn_write	= (board->has_ao_fifo)
+					? cb_pcidas_ao_fifo_insn_write
+					: cb_pcidas_ao_nofifo_insn_write;
 
 		ret = comedi_alloc_subdev_readback(s);
 		if (ret)
 			return ret;
 
-		if (board->has_ao_fifo) {
+		if (dev->irq && board->has_ao_fifo) {
 			dev->write_subdev = s;
-			s->subdev_flags |= SDF_CMD_WRITE;
-			/* use fifo (*insn_write) instead */
-			s->insn_write = cb_pcidas_ao_fifo_winsn;
-			s->do_cmdtest = cb_pcidas_ao_cmdtest;
-			s->do_cmd = cb_pcidas_ao_cmd;
-			s->cancel = cb_pcidas_ao_cancel;
+			s->subdev_flags	|= SDF_CMD_WRITE;
+			s->do_cmdtest	= cb_pcidas_ao_cmdtest;
+			s->do_cmd	= cb_pcidas_ao_cmd;
+			s->cancel	= cb_pcidas_ao_cancel;
 		}
 	} else {
-		s->type = COMEDI_SUBD_UNUSED;
+		s->type		= COMEDI_SUBD_UNUSED;
 	}
 
 	/* 8255 */