staging: comedi: dt3000: the dt3002 board does not have analog outputs

According to the boardinfo, the dt3002 board does not have analog outputs.
The rest of the board have two 12-bit analog output channels.

Replace the 'dachan' and 'dabits' members of the boardinfo with a bit-
field flag 'has_ao'. Use the new member to conditionally initialize
the analog output subdevice.
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/dt3000.c

@@ -170,9 +170,8 @@ struct dt3k_boardtype {
 	int adchan;
 	int ai_speed;
 	const struct comedi_lrange *adrange;
-	int dachan;
-	int dabits;
 	unsigned int ai_is_16bit:1;
+	unsigned int has_ao:1;
 };
 
 static const struct dt3k_boardtype dt3k_boardtypes[] = {
@@ -181,16 +180,14 @@ static const struct dt3k_boardtype dt3k_boardtypes[] = {
 		.adchan		= 16,
 		.adrange	= &range_dt3000_ai,
 		.ai_speed	= 3000,
-		.dachan		= 2,
-		.dabits		= 12,
+		.has_ao		= 1,
 	},
 	[BOARD_DT3001_PGL] = {
 		.name		= "dt3001-pgl",
 		.adchan		= 16,
 		.adrange	= &range_dt3000_ai_pgl,
 		.ai_speed	= 3000,
-		.dachan		= 2,
-		.dabits		= 12,
+		.has_ao		= 1,
 	},
 	[BOARD_DT3002] = {
 		.name		= "dt3002",
@@ -203,34 +200,30 @@ static const struct dt3k_boardtype dt3k_boardtypes[] = {
 		.adchan		= 64,
 		.adrange	= &range_dt3000_ai,
 		.ai_speed	= 3000,
-		.dachan		= 2,
-		.dabits		= 12,
+		.has_ao		= 1,
 	},
 	[BOARD_DT3003_PGL] = {
 		.name		= "dt3003-pgl",
 		.adchan		= 64,
 		.adrange	= &range_dt3000_ai_pgl,
 		.ai_speed	= 3000,
-		.dachan		= 2,
-		.dabits		= 12,
+		.has_ao		= 1,
 	},
 	[BOARD_DT3004] = {
 		.name		= "dt3004",
 		.adchan		= 16,
 		.adrange	= &range_dt3000_ai,
 		.ai_speed	= 10000,
-		.dachan		= 2,
-		.dabits		= 12,
 		.ai_is_16bit	= 1,
+		.has_ao		= 1,
 	},
 	[BOARD_DT3005] = {
 		.name		= "dt3005",	/* a.k.a. 3004-200 */
 		.adchan		= 16,
 		.adrange	= &range_dt3000_ai,
 		.ai_speed	= 5000,
-		.dachan		= 2,
-		.dabits		= 12,
 		.ai_is_16bit	= 1,
+		.has_ao		= 1,
 	},
 };
 
@@ -681,19 +674,23 @@ static int dt3000_auto_attach(struct comedi_device *dev,
 		s->cancel	= dt3k_ai_cancel;
 	}
 
+	/* Analog Output subdevice */
 	s = &dev->subdevices[1];
-	/* ao subsystem */
-	s->type		= COMEDI_SUBD_AO;
-	s->subdev_flags	= SDF_WRITABLE;
-	s->n_chan	= 2;
-	s->maxdata	= (1 << board->dabits) - 1;
-	s->len_chanlist	= 1;
-	s->range_table	= &range_bipolar10;
-	s->insn_write	= dt3k_ao_insn_write;
-
-	ret = comedi_alloc_subdev_readback(s);
-	if (ret)
-		return ret;
+	if (board->has_ao) {
+		s->type		= COMEDI_SUBD_AO;
+		s->subdev_flags	= SDF_WRITABLE;
+		s->n_chan	= 2;
+		s->maxdata	= 0x0fff;
+		s->range_table	= &range_bipolar10;
+		s->insn_write	= dt3k_ao_insn_write;
+
+		ret = comedi_alloc_subdev_readback(s);
+		if (ret)
+			return ret;
+
+	} else {
+		s->type		= COMEDI_SUBD_UNUSED;
+	}
 
 	s = &dev->subdevices[2];
 	/* dio subsystem */