linux-kernel - Re: [PATCH 5/6] gpiolib: cdev: consolidate edge detector configuration flags

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Date:   Wed, 13 Jul 2022 12:07:29 +0200
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 <brgl@...ev.pl>,
        Linus Walleij <linus.walleij@...aro.org>,
        Dipen Patel <dipenp@...dia.com>
Subject: Re: [PATCH 5/6] gpiolib: cdev: consolidate edge detector
 configuration flags

On Wed, Jul 13, 2022 at 3:39 AM Kent Gibson <warthog618@...il.com> wrote:
>
> Combine the polarity_change flag, struct line eflags, and hte enable
> flag into a single flag variable.
>
> The combination of these flags describes the configuration state
> of the edge detector, so formalize and clarify that by combining
> them into a single variable, edflags, in struct line.
>
> The edflags is a subset of the GPIO_V2_LINE_FLAGsb relevant to
> the edge detector, and is also a superset of the eflags it replaces.
> The eflags name is still used to describe the subset of edflags
> corresponding to the rising/falling edge flags where edflags is
> masked down to that subset.
>
> This consolidation reduces the number of variables being passed,
> simplifies state comparisons, and provides a more extensible
> foundation should additional edge sources be integrated in the
> future.

I believe that you have checked this from a locking perspective, so we
won't have worse lock contamination, if any.

...

>         struct linereq *lr;
>         struct gpio_v2_line_event le;
>         int level;
> -       u64 eflags;
> +       u64 edflags;

I would at the same time move it up before `int level;`.

...

> +       int level = -1, diff_seqno;
> +       u64 eflags, edflags = READ_ONCE(line->edflags);

Ditto.

...

>         u32 debounce_period_us;
>         unsigned long irqflags = 0;
>         int irq, ret;
> +       u64 eflags;

Ditto for similarity.

-- 
With Best Regards,
Andy Shevchenko