linux-kernel - Re: [PATCH v2 0/9] gpio: Get rid of ARCH_NR

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Date:   Wed, 7 Sep 2022 11:58:28 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        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>,
        Davide Ciminaghi <ciminaghi@...dd.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "open list:GENERIC INCLUDE/ASM HEADER FILES" 
        <linux-arch@...r.kernel.org>,
        linux-doc <linux-doc@...r.kernel.org>, x86@...nel.org
Subject: Re: [PATCH v2 0/9] gpio: Get rid of ARCH_NR_GPIOS (v2)

On Fri, Sep 2, 2022 at 2:42 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 from 512 upwards, allowing approx 2 millions
> of GPIOs.
>
> In the meantime, add a warning for drivers how are still doing
> static allocation, so that in the future the static allocation gets
> removed completely and dynamic allocation can start at base 0.
>
> Main changes in v2:
> - Adding a patch to remove sta2x11 GPIO driver instead of modifying it
> - Moving the base of dynamic allocation from 256 to 512 because there
> are drivers allocating gpios as high as 400.
>
> Christophe Leroy (8):
>   gpio: aggregator: Stop using ARCH_NR_GPIOS
>   gpio: davinci: Stop using ARCH_NR_GPIOS
>   gpiolib: Warn on drivers still using static gpiobase allocation
>   gpiolib: Get rid of ARCH_NR_GPIOS
>   Documentation: gpio: Remove text about ARCH_NR_GPIOS
>   x86: Remove CONFIG_ARCH_NR_GPIO
>   arm: Remove CONFIG_ARCH_NR_GPIO
>   arm64: Remove CONFIG_ARCH_NR_GPIO
>
> Davide Ciminaghi (1):
>   gpio: Remove sta2x11 GPIO driver
>
>  Documentation/driver-api/gpio/legacy.rst |   5 -
>  arch/arm/Kconfig                         |  21 --
>  arch/arm/include/asm/gpio.h              |   1 -
>  arch/arm64/Kconfig                       |  12 -
>  arch/x86/Kconfig                         |   5 -
>  drivers/gpio/Kconfig                     |   8 -
>  drivers/gpio/Makefile                    |   1 -
>  drivers/gpio/gpio-aggregator.c           |   7 +-
>  drivers/gpio/gpio-davinci.c              |   3 -
>  drivers/gpio/gpio-sta2x11.c              | 411 -----------------------
>  drivers/gpio/gpiolib.c                   |  13 +-
>  include/asm-generic/gpio.h               |  55 ++-
>  12 files changed, 33 insertions(+), 509 deletions(-)
>  delete mode 100644 drivers/gpio/gpio-sta2x11.c
>
> --
> 2.37.1
>

I'd like to take it through the GPIO tree if we can get acks for ARM and x86?

Bart