linux-kernel - Re: [PATCH v2] gpio: omap: do not register driver in probe()

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Message-ID: <CAJZ5v0hwJB_tYd=sgT2jPm94ypXdEhj0wuGtdOg+TZDRCocVJw@mail.gmail.com>
Date: Tue, 27 Jan 2026 21:32:59 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Danilo Krummrich <dakr@...nel.org>
Cc: gregkh@...uxfoundation.org, rafael@...nel.org, broonie@...nel.org, 
	will@...nel.org, grygorii.strashko@...com, ssantosh@...nel.org, 
	khilman@...nel.org, linusw@...nel.org, brgl@...nel.org, 
	driver-core@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	linux-omap@...r.kernel.org, linux-gpio@...r.kernel.org
Subject: Re: [PATCH v2] gpio: omap: do not register driver in probe()

On Tue, Jan 27, 2026 at 9:17 PM Danilo Krummrich <dakr@...nel.org> wrote:
>
> Commit 11a78b794496 ("ARM: OMAP: MPUIO wake updates") registers the
> omap_mpuio_driver from omap_mpuio_init(), which is called from
> omap_gpio_probe().
>
> However, it neither makes sense to register drivers from probe()
> callbacks of other drivers, nor does the driver core allow registering
> drivers with a device lock already being held.
>
> The latter was revealed by commit dc23806a7c47 ("driver core: enforce
> device_lock for driver_match_device()") leading to a potential deadlock
> condition described in [1].
>
> Additionally, the omap_mpuio_driver is never unregistered from the
> driver core, even if the module is unloaded.
>
> Hence, register the omap_mpuio_driver from the module initcall and
> unregister it in module_exit().
>
> Link: https://lore.kernel.org/lkml/DFU7CEPUSG9A.1KKGVW4HIPMSH@kernel.org/ [1]
> Fixes: dc23806a7c47 ("driver core: enforce device_lock for driver_match_device()")
> Fixes: 11a78b794496 ("ARM: OMAP: MPUIO wake updates")
> Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Signed-off-by: Danilo Krummrich <dakr@...nel.org>

Reviewed-by: Rafael J. Wysocki (Intel) <rafael@...nel.org>

> ---
>  drivers/gpio/gpio-omap.c | 22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> index e136e81794df..e39723b5901b 100644
> --- a/drivers/gpio/gpio-omap.c
> +++ b/drivers/gpio/gpio-omap.c
> @@ -799,10 +799,13 @@ static struct platform_device omap_mpuio_device = {
>
>  static inline void omap_mpuio_init(struct gpio_bank *bank)
>  {
> -       platform_set_drvdata(&omap_mpuio_device, bank);
> +       static bool registered;
>
> -       if (platform_driver_register(&omap_mpuio_driver) == 0)
> -               (void) platform_device_register(&omap_mpuio_device);
> +       platform_set_drvdata(&omap_mpuio_device, bank);
> +       if (!registered) {
> +               (void)platform_device_register(&omap_mpuio_device);
> +               registered = true;
> +       }
>  }
>
>  /*---------------------------------------------------------------------*/
> @@ -1575,13 +1578,24 @@ static struct platform_driver omap_gpio_driver = {
>   */
>  static int __init omap_gpio_drv_reg(void)
>  {
> -       return platform_driver_register(&omap_gpio_driver);
> +       int ret;
> +
> +       ret = platform_driver_register(&omap_mpuio_driver);
> +       if (ret)
> +               return ret;
> +
> +       ret = platform_driver_register(&omap_gpio_driver);
> +       if (ret)
> +               platform_driver_unregister(&omap_mpuio_driver);
> +
> +       return ret;
>  }
>  postcore_initcall(omap_gpio_drv_reg);
>
>  static void __exit omap_gpio_exit(void)
>  {
>         platform_driver_unregister(&omap_gpio_driver);
> +       platform_driver_unregister(&omap_mpuio_driver);
>  }
>  module_exit(omap_gpio_exit);
>
>
> base-commit: 63804fed149a6750ffd28610c5c1c98cce6bd377
> --
> 2.52.0
>