Hi!
2023-10-16 at 10:39, Linus Walleij wrote:
> On Sun, Oct 15, 2023 at 12:38 AM Peter Rosin <peda@xxxxxxxxxx> wrote:
>> 2023-09-02 at 21:46, Linus Walleij wrote:
>
>>> if (iio_channel_has_info(schan, IIO_CHAN_INFO_RAW) &&
>>> - iio_channel_has_info(schan, IIO_CHAN_INFO_SCALE)) {
>>> - dev_info(dev, "using raw+scale source channel\n");
>>> + (iio_channel_has_info(schan, IIO_CHAN_INFO_SCALE) ||
>>> + iio_channel_has_info(schan, IIO_CHAN_INFO_OFFSET))) {
>>> + dev_info(dev, "using raw+scale/offset source channel\n");
>>
>> If the rules really are that when not provided scale is 1 and offset 0
>> (reasonable of course) then the above still looks suspect to me. Should
>> this part not simply be
>>
>> if (iio_channel_has_info(schan, IIO_CHAN_INFO_RAW)) {
>> dev_info(dev, "using raw source channel\n");
>>
>> in that case?
>
> The patch is based on Jonathan's comment that while we currently
> support raw+scale, having just raw+offset provided is a possibility.
>
> The if()-clause above (which I guess you are commenting) is meant
> as "take this path if scale or offset or both are provided".
>
> Just raw (with neither offset or rescale) doesn't make sense, since
And I don't see why not. That's the crux.
> the AFE rescaler does just offsetting and rescaling, in that case the
> user should just use the raw channel. Also it would then take
> precedence over a processed channel (which applies rescale and
> offset internally) which doesn't make sense to me.
Why isn't it perfectly fine for a device to provide only a raw
channel and then expect that to be interpreted as the real unit?
Why would it need a processed channel when no processing is
going on? E.g. a device reporting the temp in the expected unit
in one of its registers. Or whatever with such a friendly
register.
And if the above holds, it should also be perfectly fine to run
that through the rescaler.
>
>> Or was "raw + processed" some kind of special case that we want to handle
>> as processed? If that's the case then we need to have more complex logic.
>
> Processed is on the else-path, which will be tried only when neither
> scale nor offset is provided:
>
>> } else if (iio_channel_has_info(schan, IIO_CHAN_INFO_PROCESSED)) {
>> dev_info(dev, "using processed channel\n");
>> rescale->chan_processed = true;
>
> I'm not sure I fully understood the remark, please elaborate if I got it wrong!
I agree that the patch does exactly as you intend. I question if
what you intend is correct, but since I don't know the rules, I'd
simply like to have the rules clarified.
Is that clearer?
Cheers,
Peter
