Re: [PATCH] iio: afe: iio-rescale: Support processed channels

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 13 Dec 2020 00:22:17 +0100
Peter Rosin <peda@axentia.se> wrote:

> On 2020-12-12 13:26, Linus Walleij wrote:
> > On Mon, Nov 2, 2020 at 12:22 AM Linus Walleij <linus.walleij@linaro.org> wrote:
> >   
> >> It happens that an ADC will only provide raw or processed
> >> voltage conversion channels. (adc/ab8500-gpadc.c).
> >> On the Samsung GT-I9070 this is used for a light sensor
> >> and current sense amplifier so we need to think of something.
> >>
> >> The idea is to allow processed channels and scale them
> >> with 1/1 and then the rescaler can modify the result
> >> on top.
> >>
> >> Cc: Peter Rosin <peda@axentia.se>
> >> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>  
> > 
> > Did we reach any conclusion on this? I really need to use
> > the rescaler on an ADC that only handles processed channels...
> > 
> > I'm sorry that I can't make this ADC disappear :D  
> 
> Hi!
> 
> My conclusion was that the patch is buggy since it presents inconsistent
> information. That needs to be fixed one way or the other. If the offending
> information cannot be filtered out for some reason, I don't know what to
> do. Details in my previous comment [1]. BTW, I still do not know the answer
> to the .read_avail question at the end of that message, and I don't have
> time to dig into it. Sorry.

Unless I'm missing something, I think it presents no information unless
we strangely have a driver providing read_avail for _RAW but only
_PROCESSED channels which is a bug.  I'm not that bothered about
missing information in this particular, somewhat obscure, corner case.

So I think we should take the patch as it stands.  It's missed the
merge window now anyway unfortunately.  So Peter, I would suggest we
take this and perhaps revisit to tidy up loose corners when we all have
more time.

Thanks,

Jonathan


> 
> Cheers,
> Peter
> 
> [1] https://lore.kernel.org/linux-iio/320464d8-659c-01de-0e08-34e4c744ef16@axentia.se/