Re: [PATCH v1 1/2] iio: mtk-auxadc: add support IIO_CHAN_INFO_RAW case

On Fri, 13 Aug 2021 11:46:24 +0800
hui.liu [off-list ref] wrote:

On Thu, 2021-08-12 at 19:07 +0100, Jonathan Cameron wrote:

quoted

On Thu, 12 Aug 2021 13:48:43 +0800
Hui Liu [off-list ref] wrote:
  

quoted

Add support IIO_CHAN_INFO_RAW case.  

Why?

We almost never support both RAW and PROCESSED as userspace should be
fine to use either.  There are a few reasons we've let drivers do
this but I would like know why it matters to you and it definitely
needs to be in the patch description.
  

Hi Jonathan,

1. To support ADC consumers' different types of requirement: some
consumers want to call iio_read_channel_raw to get raw data, the others
use iio_read_channel_processed to get voltage.

Give an example of the consumer using the raw channel readback (without
acess to any scaling information?)

2. In our origin driver, if consumer call iio_read_channel_processed,
read back value is raw data. 

Could we use SCALE instead of PROCESSED in patch for next version, or
what's your suggestion?

That would unfortunately be a userspace ABI change.  We can add interfaces
but taking them away is normally a problem :( 

Your reasons here are fine, subject to information on what consumer cares
about having _RAW, please resend the patch with this information added
to the description.

Thanks,

Jonathan

Thanks.

quoted

quoted

Signed-off-by: Hui Liu <redacted>
---
 drivers/iio/adc/mt6577_auxadc.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/mt6577_auxadc.c

b/drivers/iio/adc/mt6577_auxadc.c
index 79c1dd68b909..e995d43287b2 100644

--- a/drivers/iio/adc/mt6577_auxadc.c
+++ b/drivers/iio/adc/mt6577_auxadc.c

@@ -60,7 +60,8 @@ static const struct mtk_auxadc_compatible

mt6765_compat = {
 		.type = IIO_VOLTAGE,				   
 \
 		.indexed = 1,					   
 \
 		.channel = (idx),				    \
-		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), \
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |	   
 \
+				      BIT(IIO_CHAN_INFO_PROCESSED), \
 }
 
 static const struct iio_chan_spec mt6577_auxadc_iio_channels[] = {

@@ -181,6 +182,19 @@ static int mt6577_auxadc_read_raw(struct

iio_dev *indio_dev,
 	struct mt6577_auxadc_device *adc_dev = iio_priv(indio_dev);
 
 	switch (info) {
+	case IIO_CHAN_INFO_RAW:
+		*val = mt6577_auxadc_read(indio_dev, chan);
+		if (*val < 0) {
+			dev_notice(indio_dev->dev.parent,
+				"failed to sample data on
channel[%d]\n",
+				chan->channel);
+			return *val;
+		}
+		if (adc_dev->dev_comp->sample_data_cali)
+			*val = mt_auxadc_get_cali_data(*val, true);
+
+		return IIO_VAL_INT;
+
 	case IIO_CHAN_INFO_PROCESSED:
 		*val = mt6577_auxadc_read(indio_dev, chan);
 		if (*val < 0) {  

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