[PATCH 20/21] staging: comedi: ni_at_ao: fix analog output ranges

[H Hartley Sweeten]

Each analog output channel is individually configurable. The current
analog output 'range_table' selection in this driver assumes that all
the channels are configured as either bipolar or unipolar. User option[2]
is then used during the attach to select the range_table to use.

Add a comedi_lrange table to allow the user to specify the actual range
to use for each channel.

Make sure the approriate DAC2S bit is set in the CFG2 register when writing
straight binary unipolar values to the DAC. Also, the data only needs to
be munged to two's complement when writing bipolar values.

Signed-off-by: H Hartley Sweeten <hsweeten at visionengravers.com>
Cc: Ian Abbott <abbotti at mev.co.uk>
Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 drivers/staging/comedi/drivers/ni_at_ao.c | 41 ++++++++++++++++++++++++++-----
 1 file changed, 35 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/comedi/drivers/ni_at_ao.c b/drivers/staging/comedi/drivers/ni_at_ao.c
index 10e3e947..e483c7e 100644
--- a/drivers/staging/comedi/drivers/ni_at_ao.c
+++ b/drivers/staging/comedi/drivers/ni_at_ao.c
@@ -29,9 +29,6 @@
  *   [0] - I/O port base address
  *   [1] - IRQ (unused)
  *   [2] - DMA (unused)
- *   [3] - analog output range, set by jumpers on hardware
- *         0 for -10 to 10V bipolar
- *         1 for 0V to 10V unipolar
  */
 
 #include <linux/module.h>
@@ -99,6 +96,32 @@
 #define ATAO_2_RTSISHFT_RSI	(1 << 0)
 #define ATAO_2_RTSISTRB_REG	0x07
 
+/*
+ * Each Analog Output channel can be configured indepentently to
+ * have either a bipolar (factory setting) or unipolar output.
+ * This selection is done with jumpers on the board.
+ *
+ * There are also jumpers to select if the channel uses the internal
+ * 10V reference voltage (factory default) or an exteral reference
+ * voltage applied to the EXTREFx pin on the I/O connector. Each
+ * EXTREFx signal is shared by two DACs that are in the same chip;
+ * that is DAC0 and DAC1 share EXTREF0, DAC2 and DAC3 share EXTREF2,
+ * etc. Each channel is individually configured.
+ *
+ * The following ranges cover all the configuration options. The user
+ * must select the correct range, based on the board configuration,
+ * to correctly calculate the values needed to produce a given output
+ * voltage.
+ */
+static const struct comedi_lrange atao_range = {
+	4, {
+		BIP_RANGE(10),		/* internal bipolar */
+		UNI_RANGE(10),		/* internal unipolar */
+		RANGE_ext(-1, 1),	/* external bipolar */
+		RANGE_ext(0, 1)		/* external unipolar */
+	}
+};
+
 struct atao_board {
 	const char *name;
 	int n_ao_chans;
@@ -143,9 +166,14 @@ static int atao_ao_insn_write(struct comedi_device *dev,
 {
 	struct atao_private *devpriv = dev->private;
 	unsigned int chan = CR_CHAN(insn->chanspec);
+	unsigned int range = CR_RANGE(insn->chanspec);
 	unsigned int val;
 	int i;
 
+	/* enable straight binary format for unipolar ranges */
+	if (comedi_range_is_unipolar(s, range))
+		outw(ATAO_CFG2_DACS(chan), dev->iobase + ATAO_CFG2_REG);
+
 	if (chan == 0)
 		atao_select_reg_group(dev, 1);
 
@@ -153,8 +181,9 @@ static int atao_ao_insn_write(struct comedi_device *dev,
 		val = data[i];
 		devpriv->ao_readback[chan] = val;
 
-		/* munge offset binary (unsigned) to two's complement */
-		val = comedi_offset_munge(s, val);
+		/* bipolar ranges use two's complement format */
+		if (comedi_range_is_bipolar(s, range))
+			val = comedi_offset_munge(s, val);
 		outw(val, dev->iobase + ATAO_AO_REG(chan));
 	}
 
@@ -361,7 +390,7 @@ static int atao_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 	s->subdev_flags	= SDF_WRITABLE;
 	s->n_chan	= board->n_ao_chans;
 	s->maxdata	= 0x0fff;
-	s->range_table	= it->options[3] ? &range_unipolar10 : &range_bipolar10;
+	s->range_table	= &atao_range;
 	s->insn_write	= atao_ao_insn_write;
 	s->insn_read	= atao_ao_insn_read;
 
-- 
1.8.3.2