On 11/01/17 14:39, Jonathan Cameron wrote:
>
>
> On 11 January 2017 10:48:39 GMT+00:00, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
>> When a consumer calls iio_read_channel_processed() the IIO core
>> tries to apply scaling to the value, but if the channel only
>> supports reading raw values, we should return that raw value
>> to the cosumer instead of an error.
>>
>> This is what userspace is expected to do with sensors only
>> providing raw values so the kernel should do the same, so as to
>> avoid adding scaling boilerplate to drivers for hardware that
>> actually return processed values from raw reads.
> Hmm. I guess this is reasonable as it would be correct to have a raw value if the scale was 1
> and hence not supplied, but there was an offset
> If neither is supplied so scale is 1 and offset 0
> then having it as raw is a bug.
>
> Come to think of it the raw element is only useful on the case where we have no known units.
> Otherwise the absence of offset and scale alone would indicate a processed value.
>
> Upshot is I agree with change but might add info to patch message when I apply it. Arguably
> userspace should be specifically indicating that there is no known transform (perhaps by not
> listing units) rather than sweeping it under the carpet. This is perfectly valid for many intensity
> of reflection proximity sensors where the meaning of the value is dependant on the material which we can't know.
>
>
> Fun fun fun
Applied with a note about the above.
Thanks,
Jonathan
>
> Jonathan
>>
>> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
>> ---
>> drivers/iio/inkern.c | 10 ++++++++--
>> 1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
>> index b0f4630a163f..7a13535dc3e9 100644
>> --- a/drivers/iio/inkern.c
>> +++ b/drivers/iio/inkern.c
>> @@ -601,8 +601,14 @@ static int
>> iio_convert_raw_to_processed_unlocked(struct iio_channel *chan,
>>
>> scale_type = iio_channel_read(chan, &scale_val, &scale_val2,
>> IIO_CHAN_INFO_SCALE);
>> - if (scale_type < 0)
>> - return scale_type;
>> + if (scale_type < 0) {
>> + /*
>> + * Just pass raw values as processed if no scaling is
>> + * available.
>> + */
>> + *processed = raw;
>> + return 0;
>> + }
>>
>> switch (scale_type) {
>> case IIO_VAL_INT:
>
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