linux-kernel - Re: [PATCH v2 2/5] gpiolib: cdev: relocate debounce_period_us from struct gpio

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Date:   Thu, 14 Dec 2023 17:03:03 +0200
From:   Andy Shevchenko <andy@...nel.org>
To:     Kent Gibson <warthog618@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        brgl@...ev.pl, linus.walleij@...aro.org
Subject: Re: [PATCH v2 2/5] gpiolib: cdev: relocate debounce_period_us from
 struct gpio_desc

On Thu, Dec 14, 2023 at 05:58:11PM +0800, Kent Gibson wrote:
> Store the debounce period for a requested line locally, rather than in
> the debounce_period_us field in the gpiolib struct gpio_desc.
> 
> Add a global tree of lines containing supplemental line information
> to make the debounce period available to be reported by the
> GPIO_V2_GET_LINEINFO_IOCTL and the line change notifier.

...

> +/*
> + * Used to populate gpio_v2_line_info with cdev specific fields not contained
> + * in the struct gpio_desc.
> + * A line is determined to contain supplemental information by
> + * line_is_supplemental().
> + */
> +static struct {
> +	/* a rbtree of the struct lines containing the supplemental info */
> +	struct rb_root tree;
> +	/* covers tree */
> +	spinlock_t lock;
> +} supinfo;

...

> +static void supinfo_init(void)
> +{
> +	supinfo.tree = RB_ROOT;
> +	spin_lock_init(&supinfo.lock);
> +}

Can it be done statically?

supinfo = {
	.tree = RB_ROOT,
	.lock = __SPIN_LOCK_UNLOCKED(supinfo.lock),
};

...

> +static int __init gpiolib_cdev_init(void)
> +{
> +	supinfo_init();
> +	return 0;
> +}

A comment why it's postcore initcall?

/* postcore initcall is chosen because ... */

> +postcore_initcall(gpiolib_cdev_init);

-- 
With Best Regards,
Andy Shevchenko