[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAHp75VcngRihpfUkeKs-g+TbPnpOsZ+-Q37zDVoWp8p_2GbSvQ@mail.gmail.com>
Date: Tue, 30 Aug 2022 23:18:26 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Linus Walleij <linus.walleij@...aro.org>,
Bartosz Golaszewski <brgl@...ev.pl>,
Geert Uytterhoeven <geert+renesas@...der.be>,
Keerthy <j-keerthy@...com>, Russell King <linux@...linux.org.uk>,
Arnd Bergmann <arnd@...db.de>,
Jonathan Corbet <corbet@....net>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
Linux-Arch <linux-arch@...r.kernel.org>,
Linux Documentation List <linux-doc@...r.kernel.org>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>
Subject: Re: [PATCH v1 4/8] gpiolib: Get rid of ARCH_NR_GPIOS
On Mon, Aug 29, 2022 at 7:19 PM Christophe Leroy
<christophe.leroy@...roup.eu> wrote:
>
> Since commit 14e85c0e69d5 ("gpio: remove gpio_descs global array")
> there is no limitation on the number of GPIOs that can be allocated
> in the system since the allocation is fully dynamic.
>
> ARCH_NR_GPIOS is today only used in order to provide downwards
> gpiobase allocation from that value, while static allocation is
> performed upwards from 0. However that has the disadvantage of
> limiting the number of GPIOs that can be registered in the system.
>
> To overcome this limitation without requiring each and every
> platform to provide its 'best-guess' maximum number, rework the
> allocation to allocate upwards, allowing approx 2 millions of
> GPIOs.
>
> In order to still allow static allocation for legacy drivers, define
> GPIO_DYNAMIC_BASE with the value 256 as the start for dynamic
> allocation.
Not sure about 256, but I understand that this can only be the best guess.
--
With Best Regards,
Andy Shevchenko
Powered by blists - more mailing lists