Re: [PATCH v2] gpio: grgpio: Fix device removing

[Andy Shevchenko <andy.shevchenko@xxxxxxxxx>]

On Tue, Jun 21, 2022 at 8:40 AM Uwe Kleine-König
<u.kleine-koenig@xxxxxxxxxxxxxx> wrote:
>
> If a platform device's remove callback returns non-zero, the device core
> emits a warning and still removes the device and calls the devm cleanup
> callbacks.
>
> So it's not save to not unregister the gpiochip because on the next request
> to a GPIO the driver accesses kfree()'d memory. Also if an IRQ triggers,
> the freed memory is accessed.
>
> Instead rely on the GPIO framework to ensure that after gpiochip_remove()
> all GPIOs are freed and so the corresponding IRQs are unmapped.
>
> This is a preparation for making platform remove callbacks return void.

Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>

> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
> ---
> Changes since (implicit) v1
> (Message-Id: 20220620122933.106035-1-u.kleine-koenig@xxxxxxxxxxxxxx):
>
>  - Fix capitalisation of GPIO and IRQ in commit log
>  - Add another "are" in the third paragraph.
>  - Drop note about a potential bug in GPIO framework
>    I'm not sure there is actually a bug.
>
> Thanks to Andy Shevchenko for his feedback.
>
> Best regards
> Uwe
>
>  drivers/gpio/gpio-grgpio.c | 14 +-------------
>  1 file changed, 1 insertion(+), 13 deletions(-)
>
> diff --git a/drivers/gpio/gpio-grgpio.c b/drivers/gpio/gpio-grgpio.c
> index df563616f943..bea0e32c195d 100644
> --- a/drivers/gpio/gpio-grgpio.c
> +++ b/drivers/gpio/gpio-grgpio.c
> @@ -434,25 +434,13 @@ static int grgpio_probe(struct platform_device *ofdev)
>  static int grgpio_remove(struct platform_device *ofdev)
>  {
>         struct grgpio_priv *priv = platform_get_drvdata(ofdev);
> -       int i;
> -       int ret = 0;
> -
> -       if (priv->domain) {
> -               for (i = 0; i < GRGPIO_MAX_NGPIO; i++) {
> -                       if (priv->uirqs[i].refcnt != 0) {
> -                               ret = -EBUSY;
> -                               goto out;
> -                       }
> -               }
> -       }
>
>         gpiochip_remove(&priv->gc);
>
>         if (priv->domain)
>                 irq_domain_remove(priv->domain);
>
> -out:
> -       return ret;
> +       return 0;
>  }
>
>  static const struct of_device_id grgpio_match[] = {
>
> base-commit: f2906aa863381afb0015a9eb7fefad885d4e5a56
> --
> 2.36.1
>


-- 
With Best Regards,
Andy Shevchenko