linux-kernel - Re: [PATCH] gpio: Allow user to customise maximum number of GPIOs

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Message-ID: <CACRpkdZpwdP+1VitohznqRfhFGcLT2f+sQnmsRWwMBB3bobwAw@mail.gmail.com>
Date:   Fri, 26 Aug 2022 23:54:22 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Alexandre Courbot <gnurou@...il.com>,
        Alexandre Courbot <acourbot@...dia.com>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Jonathan Corbet <corbet@....net>,
        Russell King <linux@...linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM PORT" <linux-arm-kernel@...ts.infradead.org>,
        "open list:GENERIC INCLUDE/ASM HEADER FILES" 
        <linux-arch@...r.kernel.org>
Subject: Re: [PATCH] gpio: Allow user to customise maximum number of GPIOs

On Fri, Aug 26, 2022 at 5:08 PM Christophe Leroy
<christophe.leroy@...roup.eu> wrote:
> Le 26/08/2022 à 15:49, Linus Walleij a écrit :
> > On Thu, Aug 25, 2022 at 4:00 PM Christophe Leroy
> > <christophe.leroy@...roup.eu> wrote:
> >
> >>> Christophe? Will you take a stab at it?
> >>
> >> Which patch should I write ?
> >
> > One that removes CONFIG_ARCH_HAS_NR_GPIO entirely, then
> > allocate bases for new GPIO chips from 0 and upward instead.
> > And then see what happens.
> >
>
> Ok, I can give it a try.

Nice!

> But what do I do with:
>
> drivers/gpio/gpio-aggregator.c: bitmap = bitmap_alloc(ARCH_NR_GPIOS,
> GFP_KERNEL);

That's just used locally in that driver to loop over the arguments to the
aggregator (from the file in sysfs). I would set some arbitrary root
like
#define AGGREGATOR_MAX_GPIOS 512
and just search/replace with that.

Yours,
Linus Walleij