staging: comedi: me_daq: tidy up ai fifo/chanlist register defines

Tidy up this register usage by defining some macros to set the channel
and gain bits. Add a define for the bit that enables differential mode.

Writing to this offset puts data in the ai chanlist fifo, reading from
it gets data from the ai data fifo. For aesthetics, use the same define
to read and write the registers.
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/me_daq.c

@@ -84,13 +84,11 @@
 #define ME_DIO_PORT_A_REG		0x06	/* R | W */
 #define ME_DIO_PORT_B_REG		0x08	/* R | W */
 #define ME_TIMER_DATA_REG(x)		(0x0a + ((x) * 2))	/* - | W */
-#define ME_CHANNEL_LIST			0x0010	/* - | W */
-#define   ADC_UNIPOLAR			(1<<6)
-#define   ADC_GAIN_0			(0<<4)
-#define   ADC_GAIN_1			(1<<4)
-#define   ADC_GAIN_2			(2<<4)
-#define   ADC_GAIN_3			(3<<4)
-#define ME_READ_AD_FIFO			0x0010	/* R | - */
+#define ME_AI_FIFO_REG			0x10	/* R (fifo) | W (chanlist) */
+#define   ME_AI_FIFO_CHANLIST_DIFF	BIT(7)
+#define   ME_AI_FIFO_CHANLIST_UNIPOLAR	BIT(6)
+#define   ME_AI_FIFO_CHANLIST_GAIN(x)	(((x) & 0x3) << 4)
+#define   ME_AI_FIFO_CHANLIST_CHAN(x)	(((x) & 0xf) << 0)
 #define ME_DAC_CONTROL			0x0012	/* - | W */
 #define   DAC_UNIPOLAR_D		(0<<4)
 #define   DAC_BIPOLAR_D			(1<<4)
@@ -262,7 +260,7 @@ static int me_ai_insn_read(struct comedi_device *dev,
 {
 	struct me_private_data *devpriv = dev->private;
 	unsigned int chan = CR_CHAN(insn->chanspec);
-	unsigned int rang = CR_RANGE(insn->chanspec);
+	unsigned int range = CR_RANGE(insn->chanspec);
 	unsigned int aref = CR_AREF(insn->chanspec);
 	unsigned short val;
 	int ret;
@@ -282,11 +280,12 @@ static int me_ai_insn_read(struct comedi_device *dev,
 	writew(devpriv->ctrl2, dev->mmio + ME_CTRL2_REG);
 
 	/* write to channel list fifo */
-	val = chan & 0x0f;			/* b3:b0 channel */
-	val |= (rang & 0x03) << 4;		/* b5:b4 gain */
-	val |= (rang & 0x04) << 4;		/* b6 polarity */
-	val |= ((aref & AREF_DIFF) ? 0x80 : 0);	/* b7 differential */
-	writew(val & 0xff, dev->mmio + ME_CHANNEL_LIST);
+	val = ME_AI_FIFO_CHANLIST_CHAN(chan) | ME_AI_FIFO_CHANLIST_GAIN(range);
+	if (comedi_range_is_unipolar(s, range))
+		val |= ME_AI_FIFO_CHANLIST_UNIPOLAR;
+	if (aref & AREF_DIFF)
+		val |= ME_AI_FIFO_CHANLIST_DIFF;
+	writew(val, dev->mmio + ME_AI_FIFO_REG);
 
 	/* set ADC mode to software trigger */
 	devpriv->ctrl1 |= ME_CTRL1_ADC_MODE_SOFT_TRIG;
@@ -301,7 +300,7 @@ static int me_ai_insn_read(struct comedi_device *dev,
 		return ret;
 
 	/* get value from ADC fifo */
-	val = readw(dev->mmio + ME_READ_AD_FIFO);
+	val = readw(dev->mmio + ME_AI_FIFO_REG);
 	val = (val ^ 0x800) & 0x0fff;
 	data[0] = val;