The ai (*insn_read) allows differential analog inputs but the subdevice
initialization is missing the SDF_DIFF subdev_flag to allow the user to
select this mode. Fix the subdevice init.
According to the manual, differential operation only works with the
first 8 channels and bipolar ranges. Add a check to the (*insn_read) to
ensure this.
Signed-off-by: H Hartley Sweeten <hswee...@visionengravers.com>
Cc: Ian Abbott <abbo...@mev.co.uk>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
drivers/staging/comedi/drivers/me_daq.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/staging/comedi/drivers/me_daq.c
b/drivers/staging/comedi/drivers/me_daq.c
index 9110405..cfb3566 100644
--- a/drivers/staging/comedi/drivers/me_daq.c
+++ b/drivers/staging/comedi/drivers/me_daq.c
@@ -246,6 +246,15 @@ static int me_ai_insn_read(struct comedi_device *dev,
unsigned short val;
int ret;
+ /*
+ * For differential operation, there are only 8 input channels
+ * and only bipolar ranges are available.
+ */
+ if (aref & AREF_DIFF) {
+ if (chan > 7 || comedi_range_is_unipolar(s, range))
+ return -EINVAL;
+ }
+
/* stop any running conversion */
devpriv->ctrl1 &= ~ME_CTRL1_ADC_MODE_MASK;
writew(devpriv->ctrl1, dev->mmio + ME_CTRL1_REG);
@@ -472,7 +481,7 @@ static int me_auto_attach(struct comedi_device *dev,
s = &dev->subdevices[0];
s->type = COMEDI_SUBD_AI;
- s->subdev_flags = SDF_READABLE | SDF_COMMON;
+ s->subdev_flags = SDF_READABLE | SDF_COMMON | SDF_DIFF;
s->n_chan = 16;
s->maxdata = 0x0fff;
s->len_chanlist = 16;
--
2.5.1
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