linux-kernel - Re: [PATCH v2 08/11] gpio: cdev: Leverage revocable for accessing struct gpio

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Message-ID: <CAMRc=Mf_SvTzYZ23OJy-dTU4XCDTcUfsCAqJw2TxtrOXJvbUvA@mail.gmail.com>
Date: Wed, 4 Feb 2026 14:02:37 +0100
From: Bartosz Golaszewski <brgl@...nel.org>
To: Tzung-Bi Shih <tzungbi@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Danilo Krummrich <dakr@...nel.org>, Linus Walleij <linusw@...nel.org>, 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
Subject: Re: [PATCH v2 08/11] gpio: cdev: Leverage revocable for accessing
 struct gpio_chip

On Tue, Feb 3, 2026 at 7:12 AM Tzung-Bi Shih <tzungbi@...nel.org> wrote:
>
> Struct gpio_device now provides a revocable provider to the underlying
> struct gpio_chip.  Leverage revocable for accessing the struct
> gpio_chip.
>
> Signed-off-by: Tzung-Bi Shih <tzungbi@...nel.org>
> ---

[snip]

> @@ -1432,10 +1433,10 @@ static long linereq_ioctl(struct file *file, unsigned int cmd,
>  {
>         struct linereq *lr = file->private_data;
>         void __user *ip = (void __user *)arg;
> +       struct gpio_chip *gc;
>
> -       guard(srcu)(&lr->gdev->srcu);
> -
> -       if (!rcu_access_pointer(lr->gdev->chip))
> +       REVOCABLE_TRY_ACCESS_WITH(lr->gdev->chip_rp, gc);
> +       if (!gc)
>                 return -ENODEV;
>

If we're doing this, then I'd love to see something that actually
makes the code smaller like:

REVOCABLE_TRY_ACCESS_WITH_OR_RETURN(lr->gdev->chip_rp, gc, -ENODEV);

which would allow dropping the repeated checks.

Bart