linux-kernel - Re: [PATCH v2 5/8] pinctrl: nuvoton: Add driver for WPCM450

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Message-ID: <CACRpkdb_zGz4+8R0=ORCbbbVeJVkLqBG2CDXAzi2VAA7-PPZ6A@mail.gmail.com>
Date:   Fri, 10 Dec 2021 02:41:45 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     zweiss@...inix.com
Cc:     Jonathan Neuschäfer <j.neuschaefer@....net>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Tomer Maimon <tmaimon77@...il.com>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v2 5/8] pinctrl: nuvoton: Add driver for WPCM450

On Thu, Dec 9, 2021 at 9:26 AM Zev Weiss <zweiss@...inix.com> wrote:
> On Wed, Dec 08, 2021 at 05:58:30AM PST, Jonathan Neuschäfer wrote:

> >> BIT()
> >
> >I'll use it, but in this case, I think it doesn't simplify much the
> >whole expression all that much. Is there perhaps a macro that
> >constructs a continuous bitmask of N bits, perhaps additionally
> >left-shifted by M bits?
> >
> >Maybe somewhere in the bitmap_* API...
> >
>
> There's GENMASK(), though it takes a high bit and low bit rather than a
> bit position and count, so it'd require a small bit of arithmetic, e.g.
>
>   lastbit = gpio->first_irq_bit + gpio->num_irqs - 1;
>   ours = GENMASK(lastbit, gpio->first_irq_bit);
>
> or a manual shift:
>
>   ours = GENMASK(gpio->num_irqs - 1, 0) << gpio->first_irq_bit;

I think this can be handled with FIELD_PREP() from
<linux/bitfield.h>? Some examples at the top of the
header.

Yours,
Linus Walleij