RE: [PATCH v2 5/5] iio: dac: ltc2664: Add driver for LTC2664 and LTC2672

[Paller, Kim Seer]

> -----Original Message-----
> From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> Sent: Friday, May 24, 2024 1:02 AM
> To: Paller, Kim Seer <KimSeer.Paller@xxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-iio@xxxxxxxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; Jonathan Cameron <jic23@xxxxxxxxxx>; David
> Lechner <dlechner@xxxxxxxxxxxx>; Lars-Peter Clausen <lars@xxxxxxxxxx>;
> Liam Girdwood <lgirdwood@xxxxxxxxx>; Mark Brown <broonie@xxxxxxxxxx>;
> Dimitri Fedrau <dima.fedrau@xxxxxxxxx>; Krzysztof Kozlowski
> <krzk+dt@xxxxxxxxxx>; Rob Herring <robh@xxxxxxxxxx>; Conor Dooley
> <conor+dt@xxxxxxxxxx>; Hennerich, Michael
> <Michael.Hennerich@xxxxxxxxxx>; Nuno Sá <noname.nuno@xxxxxxxxx>
> Subject: Re: [PATCH v2 5/5] iio: dac: ltc2664: Add driver for LTC2664 and
> LTC2672
> 
> [External]
> 
> On Thu, 23 May 2024 11:19:09 +0800
> Kim Seer Paller <kimseer.paller@xxxxxxxxxx> wrote:
> 
> > LTC2664 4 channel, 16 bit Voltage Output SoftSpan DAC
> > LTC2672 5 channel, 16 bit Current Output Softspan DAC
> >
> > Co-developed-by: Michael Hennerich <michael.hennerich@xxxxxxxxxx>
> > Signed-off-by: Michael Hennerich <michael.hennerich@xxxxxxxxxx>
> > Signed-off-by: Kim Seer Paller <kimseer.paller@xxxxxxxxxx>
> Hi Kim,
> 
> A few minor things inline,
> 
> Jonathan
> 
> > diff --git a/drivers/iio/dac/ltc2664.c b/drivers/iio/dac/ltc2664.c
> > new file mode 100644
> > index 000000000000..488b841e6c66
> > --- /dev/null
> > +++ b/drivers/iio/dac/ltc2664.c
> > @@ -0,0 +1,802 @@
> 
> 
> > +static int ltc2664_set_span(const struct ltc2664_state *st, int min, int max,
> > +			    int chan)
> > +{
> > +	const struct ltc2664_chip_info *chip_info = st->chip_info;
> > +	const int (*span_helper)[2] = chip_info->span_helper;
> > +	int span, ret;
> > +
> > +	st->iio_channels[chan].type = chip_info->measurement_type;
> > +
> > +	for (span = 0; span < chip_info->num_span; span++) {
> > +		if (min == span_helper[span][0] && max ==
> span_helper[span][1])
> > +			break;
> > +	}
> 
> Sanity check for no match?
> 
> > +
> > +	ret = regmap_write(st->regmap, LTC2664_CMD_SPAN_N(chan),
> > +			   (chip_info->id == LTC2672) ? span + 1 : span);
> > +	if (ret)
> > +		return ret;
> > +
> > +	return span;
> > +}
> > +
> > +static int ltc2664_channel_config(struct ltc2664_state *st)
> > +{
> > +	const struct ltc2664_chip_info *chip_info = st->chip_info;
> > +	struct device *dev = &st->spi->dev;
> > +	u32 reg, tmp[2], mspan;
> > +	int ret, span;
> > +
> > +	mspan = LTC2664_MSPAN_SOFTSPAN;
> > +	ret = device_property_read_u32(dev, "adi,manual-span-operation-
> config",
> > +				       &mspan);
> > +	if (!ret) {
> > +		if (!chip_info->manual_span_support)
> > +			return dev_err_probe(dev, -EINVAL,
> > +			       "adi,manual-span-operation-config not
> supported\n");
> > +
> > +		if (mspan > ARRAY_SIZE(ltc2664_mspan_lut))
> > +			return dev_err_probe(dev, -EINVAL,
> > +			       "adi,manual-span-operation-config not in
> range\n");
> > +	}
> > +
> > +	st->rfsadj = 20000;
> > +	ret = device_property_read_u32(dev, "adi,rfsadj-ohms", &st->rfsadj);
> > +	if (!ret) {
> > +		if (!chip_info->rfsadj_support)
> > +			return dev_err_probe(dev, -EINVAL,
> > +					     "adi,rfsadj-ohms not supported\n");
> > +
> > +		if (st->rfsadj < 19000 || st->rfsadj > 41000)
> > +			return dev_err_probe(dev, -EINVAL,
> > +					     "adi,rfsadj-ohms not in range\n");
> > +	}
> > +
> > +	device_for_each_child_node_scoped(dev, child) {
> > +		struct ltc2664_chan *chan;
> > +
> > +		ret = fwnode_property_read_u32(child, "reg", &reg);
> > +		if (ret)
> > +			return dev_err_probe(dev, ret,
> > +					     "Failed to get reg property\n");
> > +
> > +		if (reg >= chip_info->num_channels)
> > +			return dev_err_probe(dev, -EINVAL,
> > +					     "reg bigger than: %d\n",
> > +					     chip_info->num_channels);
> > +
> > +		chan = &st->channels[reg];
> > +
> > +		if (fwnode_property_read_bool(child, "adi,toggle-mode")) {
> > +			chan->toggle_chan = true;
> > +			/* assume sw toggle ABI */
> > +			st->iio_channels[reg].ext_info =
> ltc2664_toggle_sym_ext_info;
> 
> chan->ext_info = ...

Hi Jonathan, 

I noticed that the struct ltc2664_chan does not currently have an ext_info field.
Based on your comment, I'm considering adding this field to the structure yet 
I'd like to understand how this would interact with the iio_chan_spec. I'd see this
by adding 'st->iio_channels[reg].ext_info = chan->ext_info' after that. Is that right
approach? I'd appreciate more details on how you picture this. Thanks

Kim