linux-kernel - Re: [PATCH v2 07/14] iio: sx9310: Use long instead of int for channel bitmaps

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Message-ID: <CAHcu+VaKGNxAY_OQ4oS5NtkoDLGkv2x_VrQhZ7OvEFAnNbYZeg@mail.gmail.com>
Date:   Fri, 31 Jul 2020 09:44:34 -0600
From:   Daniel Campello <campello@...omium.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        LKML <devicetree@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Douglas Anderson <dianders@...omium.org>,
        Enrico Granata <egranata@...omium.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio <linux-iio@...r.kernel.org>
Subject: Re: [PATCH v2 07/14] iio: sx9310: Use long instead of int for channel bitmaps

On Wed, Jul 29, 2020 at 1:00 AM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Wed, Jul 29, 2020 at 4:03 AM Stephen Boyd <swboyd@...omium.org> wrote:
> > Quoting Daniel Campello (2020-07-28 16:05:13)
> > > Uses for_each_set_bit() macro to loop over channel bitmaps.
>
> ...
>
> > > +       unsigned long chan_prox_stat;
> >
> > This can be DECLARE_BITMAP(chan_prox_stat, SX9310_NUM_CHANNELS)
>
> > > +       unsigned long chan_read;
> > > +       unsigned long chan_event;
> >
> > Same for these?
All of these are eventually used by regmap_update_bits() which expects
unsigned int. I believe the extra complexity is not worth it given the
number of channels.
>
> ...
>
> > > +       prox_changed = (data->chan_prox_stat ^ val) & data->chan_event;
> >
> > I was expecting:
> >
> >
> >         bitmap_xor(&prox_changed, &data->chan_prox_stat, &val, SX9310_NUM_CHANNELS);
> >         bitmap_and(&prox_changed, &data->chan_event, SX9310_NUM_CHANNELS);
>
> I agree with this. On a small number of channels (up to 32) it will be
> reduced to simple operations, but will leave a possibility to have
> more with easy redefine.
>
> (though _and() above misses one argument AFAICT)
>
> ...
>
> > > +       unsigned long channels = 0;
> >
> > Use DECLARE_BITMAP(channels, SX9310_NUM_CHANNELS)?
>
>
> --
> With Best Regards,
> Andy Shevchenko