linux-kernel - Re: [PATCH v2] gpiolib: cdev: document that line eflags are shared

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Date:   Fri, 16 Oct 2020 17:24:14 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Kent Gibson <warthog618@...il.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v2] gpiolib: cdev: document that line eflags are shared

On Wed, Oct 14, 2020 at 12:21 PM Kent Gibson <warthog618@...il.com> wrote:
>
> The line.eflags field is shared so document this fact and highlight it
> throughout using READ_ONCE() and WRITE_ONCE() accessors.
>
> Also use a local copy of the eflags in edge_irq_thread() to ensure
> consistent control flow even if eflags changes.  This is only a defensive
> measure as edge_irq_thread() is currently disabled when the eflags are
> changed.

> -       if (line->eflags == (GPIO_V2_LINE_FLAG_EDGE_RISING |
> -                            GPIO_V2_LINE_FLAG_EDGE_FALLING)) {
> +       eflags = READ_ONCE(line->eflags);
> +       if (eflags == (GPIO_V2_LINE_FLAG_EDGE_RISING |
> +                      GPIO_V2_LINE_FLAG_EDGE_FALLING)) {

Hmm... side note: perhaps at some point

#define GPIO_V2_LINE_FLAG_EDGE_BOTH  \
        (GPIO_V2_LINE_FLAG_EDGE_RISING | GPIO_V2_LINE_FLAG_EDGE_FALLING)

       if (eflags == GPIO_V2_LINE_FLAG_EDGE_BOTH) {

?

-- 
With Best Regards,
Andy Shevchenko