linux-kernel - Re: [PATCH v2 07/11] gpio: Add revocable provider handle for struct gpio

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Message-ID: <CAMRc=MdYeoMxNFYeX_9S-M286aUjnsxLyy9_apmfPR4NeqVouw@mail.gmail.com>
Date: Wed, 4 Feb 2026 07:58:44 -0500
From: Bartosz Golaszewski <brgl@...nel.org>
To: Tzung-Bi Shih <tzungbi@...nel.org>
Cc: Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>, 
	Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
	Wolfram Sang <wsa+renesas@...g-engineering.com>, Jason Gunthorpe <jgg@...dia.com>, 
	Johan Hovold <johan@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, chrome-platform@...ts.linux.dev, 
	Dan Williams <dan.j.williams@...el.com>, linux-gpio@...r.kernel.org, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Danilo Krummrich <dakr@...nel.org>, Bartosz Golaszewski <brgl@...ev.pl>, Linus Walleij <linusw@...nel.org>
Subject: Re: [PATCH v2 07/11] gpio: Add revocable provider handle for struct gpio_chip

On Tue, 3 Feb 2026 07:10:54 +0100, Tzung-Bi Shih <tzungbi@...nel.org> said:
> The underlying chip can be removed asynchronously.  `gdev->srcu` is used
> to ensure the synchronization before accessing `gdev->chip`.
>
> Revocable encapsulates the details.  Add revocable provider handle for
> the corresponding struct gpio_chip in struct gpio_device so that it can
> start to hide the synchronization details.
>
> Signed-off-by: Tzung-Bi Shih <tzungbi@...nel.org>
> ---

[snip]

> diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
> index 3abb90385829..cd136d5b52e9 100644
> --- a/drivers/gpio/gpiolib.h
> +++ b/drivers/gpio/gpiolib.h
> @@ -52,6 +52,7 @@
>   * @device_notifier: used to notify character device wait queues about the GPIO
>   *                   device being unregistered
>   * @srcu: protects the pointer to the underlying GPIO chip
> + * @chip_rp: revocable provider handle for the corresponding struct gpio_chip.
>   * @pin_ranges: range of pins served by the GPIO driver
>   *
>   * This state container holds most of the runtime variable data
> @@ -79,6 +80,7 @@ struct gpio_device {
>  	struct workqueue_struct	*line_state_wq;
>  	struct blocking_notifier_head device_notifier;
>  	struct srcu_struct	srcu;
> +	struct revocable_provider __rcu *chip_rp;
>

Why __rcu? This doesn't live in a different address space, only the internal
resource it protects does. If anything - this could be __attribute__((noderef))
but even that is questionable as this is an opaque structure.

Bart

>  #ifdef CONFIG_PINCTRL
>  	/*
> --
> 2.53.0.rc2.204.g2597b5adb4-goog
>
>