linux-kernel - Re: [PATCH] pinctrl: at91-pio4: implement .get_multiple and .set

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Message-ID: <CACRpkdbziti1yBY_mZaGPg+jHVPR8vtRm8oNZBqt6e+m2wh67A@mail.gmail.com>
Date:   Thu, 12 Sep 2019 14:46:32 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pinctrl: at91-pio4: implement .get_multiple and .set_multiple

On Wed, Sep 11, 2019 at 10:11 AM Alexandre Belloni
<alexandre.belloni@...tlin.com> wrote:
> On 11/09/2019 01:27:10+0100, Linus Walleij wrote:

> > > +#if ATMEL_PIO_NPINS_PER_BANK != BITS_PER_LONG
> >
> > Should it not be > rather than != ?
>
> Realistically, the only case that could happen would be
> ATMEL_PIO_NPINS_PER_BANK == 32 and BITS_PER_LONG ==64. so I would go for
> ATMEL_PIO_NPINS_PER_BANK < BITS_PER_LONG

OK I see.

> > > +               word = BIT_WORD(bank * ATMEL_PIO_NPINS_PER_BANK);
> > > +               offset = bank * ATMEL_PIO_NPINS_PER_BANK % BITS_PER_LONG;
> > > +#endif
> >
> > This doesn't look good for multiplatform kernels.
>
> I don't think we have multiplatform kernels that run both in 32 and 64
> bits. I don't believe ATMEL_PIO_NPINS_PER_BANK will ever change, it has
> been 32 on all the atmel SoCs since 2001.

So there is a bit missing from the commit message: the info that
the same driver is being used on 32 and 64 bit builds, and that is
the reason we allow compile-time ifdef things.

Can you add this to the commit message, or maybe
inline in the code, or both?

It confused me so it will confuse others.

Yours,
Linus Walleij