linux-kernel - Re: [PATCH-next 07/20] gpio: gpio-omap: simplify omap_gpio_get

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Message-ID: <CACRpkdYaropisZADA61LF_0aUmWzi44c7pQbEUV92r06Qu3m_w@mail.gmail.com>
Date:   Wed, 12 Jun 2019 10:47:23 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     Russell King <rmk@....linux.org.uk>,
        Tony Lindgren <tony@...mide.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Russell King <rmk+kernel@...linux.org.uk>
Subject: Re: [PATCH-next 07/20] gpio: gpio-omap: simplify omap_gpio_get_direction()

On Mon, Jun 10, 2019 at 7:12 PM Grygorii Strashko
<grygorii.strashko@...com> wrote:

> From: Russell King <rmk+kernel@...linux.org.uk>
>
> Architectures are single-copy atomic, which means that simply reading
> a register is an inherently atomic operation.  There is no need to
> take a spinlock here.
>
> Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>

Patch applied.

This makes me wonder how many more instances we have
of this kind of mistake in the kernel :/ I guess it is mostly
harmless but it sure makes for massive code complexity.

I would sure like e.g. drivers/gpio/gpio-mmio.c to avoid
taking locks on architectures where this is not a problem
given it is used on a plethora of architectures.

Yours,
Linus Walleij