From: Linus Walleij <linus.walleij@linaro.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>,
Bartosz Golaszewski <brgl@bgdev.pl>,
Jonathan Corbet <corbet@lwn.net>,
Russell King <linux@armlinux.org.uk>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>,
"moderated list:ARM PORT" <linux-arm-kernel@lists.infradead.org>,
"open list:GENERIC INCLUDE/ASM HEADER FILES"
<linux-arch@vger.kernel.org>
Subject: Re: [PATCH] gpio: Allow user to customise maximum number of GPIOs
Date: Thu, 18 Aug 2022 13:13:30 +0200 [thread overview]
Message-ID: <CACRpkdbhbwBe=jU5prifXCYUXPqULhst0se3ZRH+sWOh9XeoLQ@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a1Vh1Uehuin-u5QrTO5qh+t0aK_hA-QZwqc00Db_+MKcw@mail.gmail.com>
On Thu, Aug 18, 2022 at 11:48 AM Arnd Bergmann <arnd@arndb.de> wrote:
> As I understood, the problem that Christophe ran into is that the
> dynamic registration of additional gpio chips is broken because
> it unregisters the chip if the number space is exhausted:
>
> base = gpiochip_find_base(gc->ngpio);
> if (base < 0) {
> ret = base;
> spin_unlock_irqrestore(&gpio_lock, flags);
> goto err_free_label;
> }
>
> From the git history, it looks like this error was never handled gracefully
> even if the intention was to keep going without a number assignment,
> so there are probably other bugs one runs into after changing this.
Hm that should be possible to get rid of altogether? I suppose it is only
there to satisfy
static inline bool gpio_is_valid(int number)
{
return number >= 0 && number < ARCH_NR_GPIOS;
}
?
If using GPIO descriptors, any descriptor != NULL is valid,
this one is just used with legacy GPIOs. Maybe we should just
delete gpio_is_valid() everywhere and then drop the cap?
I think there may be systems and users that still depend on GPIO base
numbers being assigned from ARCH_NR_GPIOS and
downwards (userspace GPIO numbers in sysfs will also change...)
otherwise we could assign from 0 and up.
Right now the safest would be:
Assign from 512 and downwards until we hit 0 then assign
from something high, like U32_MAX and downward.
That requires dropping gpio_is_valid() everywhere.
If we wanna be bold, just delete gpio_is_valid() and assign
bases from 0 and see what happens. But I think that will
lead to regressions.
Yours,
Linus Walleij
next prev parent reply other threads:[~2022-08-18 11:13 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-09 10:40 [PATCH] gpio: Allow user to customise maximum number of GPIOs Christophe Leroy
2022-08-11 19:57 ` H. Peter Anvin
2022-08-12 21:58 ` Andy Shevchenko
2022-08-12 23:21 ` H. Peter Anvin
2022-08-17 17:21 ` Christophe Leroy
2022-08-17 17:46 ` Arnd Bergmann
2022-08-18 6:00 ` Christophe Leroy
2022-08-18 8:25 ` Arnd Bergmann
2022-08-18 9:33 ` Linus Walleij
2022-08-18 9:47 ` Arnd Bergmann
2022-08-18 11:13 ` Linus Walleij [this message]
2022-08-18 11:33 ` Arnd Bergmann
2022-08-18 12:25 ` Linus Walleij
2022-08-18 12:46 ` Arnd Bergmann
2022-08-18 13:11 ` Christophe Leroy
2022-08-25 13:36 ` Linus Walleij
2022-08-25 14:00 ` Christophe Leroy
2022-08-26 13:49 ` Linus Walleij
2022-08-26 15:08 ` Christophe Leroy
2022-08-26 21:54 ` Linus Walleij
2022-08-28 9:06 ` Christophe Leroy
2022-08-28 10:04 ` Arnd Bergmann
2022-08-30 7:58 ` Davide Ciminaghi
2022-08-31 13:32 ` Linus Walleij
2022-08-31 14:12 ` Davide Ciminaghi
2022-08-31 21:07 ` Andy Shevchenko
2022-08-31 21:48 ` Davide Ciminaghi
2022-08-30 8:33 ` Alessandro Rubini
2022-08-30 9:03 ` Christophe Leroy
2022-08-28 11:35 ` Linus Walleij
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