linux-kernel - Re: [PATCH 3/3] iio: addac: ad74413r: correct comparator gpio getters mask usage

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Date:   Mon, 10 Jan 2022 20:22:20 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Cosmin Tanislav <demonsingur@...il.com>
Cc:     cosmin.tanislav@...log.com, Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH 3/3] iio: addac: ad74413r: correct comparator gpio getters
 mask usage

On Mon, Jan 10, 2022 at 6:55 PM Cosmin Tanislav <demonsingur@...il.com> wrote:
> On 1/9/22 14:13, Andy Shevchenko wrote:
> > On Fri, Jan 7, 2022 at 7:34 AM Cosmin Tanislav <demonsingur@...il.com> wrote:

...

> >> -       status &= AD74413R_DIN_COMP_OUT_SHIFT_X(real_offset);
> >> +       status &= BIT(real_offset);
> >
> > But this is completely different.
>
> What do you mean by this is completely different?
>
> It was broken before, it is fixed now. Indeed, I'm missing
> the Fixes tag, if that's what you meant.

Yeah, I explained myself below. I think you got the idea.

...

> >> +       bitmap_zero(bits, chip->ngpio);
> >> +
> >>          for_each_set_bit(offset, mask, chip->ngpio) {
> >>                  unsigned int real_offset = st->comp_gpio_offsets[offset];
> >>
> >>                  if (val & BIT(real_offset))
> >> -                       *bits |= offset;
> >> +                       *bits |= BIT(offset);
> >
> > So, how was it working before? If it fixes, it should go with the
> > Fixes tag and before patch 2.
> >
> > On top of that, you may try to see if one of bitmap_*() APIs can be
> > suitable here to perform the above in a more optimal way.
> > (At least this conditional can be replaced with __asign_bit() call,
> > but I think refactoring the entire loop may reveal a better approach)
>
> I can replace the if and bitmap_zero with __assign_bit, as you
> suggested. I'm not familiar with bitmap APIs, do you have a suggestion?

For now I'm lacking any new suggestions. If you don't see any better
approaches, let's go with __assign_bit().

-- 
With Best Regards,
Andy Shevchenko