On 2021-01-04 18:11, Jonathan Cameron wrote: > On Mon, 4 Jan 2021 15:45:07 +0100 > Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > >> On Mon, Dec 14, 2020 at 5:34 PM Jonathan Cameron >> <Jonathan.Cameron@xxxxxxxxxx> wrote: >>> On Mon, 14 Dec 2020 16:30:22 +0100 Peter Rosin <peda@xxxxxxxxxx> wrote: >> >>>>>> And that gets transformed by the >>>>>> rescaler into the processed values being presented as raw, with rescaling >>>>>> added on top, but with the read_avail info for this new raw channel being >>>>>> completely wrong. >>>>>> >>>>>> For the intended driver (ab8500-gpadc) this is not the case (it has no >>>>>> read_avail for its raw channel). But it does have a raw channel, so adding >>>>>> read_avail seems easy and I can easily see other drivers already doing it. >>>>>> Haven't checked that though... >>>>> >>>>> Drat. I'd failed to register this is one of those corner cases. >>>> >>>> I'm not sure, I just browsed the code. Maybe I misread it? >>> >>> It's doing both - you were right. I think there are only a small number of >>> drivers that have that history. >>> >>> Looks superficially like it's easy enough to catch this corner case and >>> block it - so lets do that. >> >> Sorry if I am a bit confused here. I don't understand what I am supposed >> to do to proceed with using this driver with the ab8500 GPADC... >> >> Shall I fix something in the AB8500 GPADC as a prerequisite? >> In that case I think I need some more pointers... > > I confess I'm a bit lost, but I 'think' the problem we had > left was around read_avail which doesn't play well if we > it defined for the _raw value in the provider, but not the _processed value. > > So if we detect their is a _processed channel (which we are going to use) we > just need to make sure that we don't pass the read_avail for _raw through > to be exposed by the rescale driver as the consumer as it will be garbage. > Best plan is probably to just pretend the read_avail for the provider doesn't > exist in this case. > > @Peter, does that cover it of are there other similar cases? Yes, that's it. Just hide _raw in read_avail if we are proceding with _processed as _raw. > It definitely also wants a big fat comment saying why we are hiding this! Yup. Cheers, Peter
