linux-kernel - Re: [PATCH] drm/bridge: anx7625: Check GPIO description to avoid crash

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Message-ID: <CA+Px+wUc8+5HtkS8y4b9aw7m+wLS+zC1em6VKRNog1QKnJrZ=Q@mail.gmail.com>
Date:   Thu, 18 Nov 2021 12:52:14 +0800
From:   Tzung-Bi Shih <tzungbi@...gle.com>
To:     Xin Ji <xji@...logixsemi.com>
Cc:     a.hajda@...sung.com, narmstrong@...libre.com,
        dan.carpenter@...cle.com, robert.foss@...aro.org,
        Laurent.pinchart@...asonboard.com, jonas@...boo.se,
        jernej.skrabec@...il.com, airlied@...ux.ie, daniel@...ll.ch,
        sam@...nborg.org, pihsun@...omium.org, maxime@...no.tech,
        drinkcat@...gle.com, hsinyi@...omium.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        bliang@...logixsemi.com, qwen@...logixsemi.com
Subject: Re: [PATCH] drm/bridge: anx7625: Check GPIO description to avoid crash

On Thu, Nov 18, 2021 at 11:11 AM Xin Ji <xji@...logixsemi.com> wrote:
> @@ -1098,9 +1098,18 @@ static void anx7625_init_gpio(struct anx7625_data *platform)
>         /* Gpio for chip power enable */
>         platform->pdata.gpio_p_on =
>                 devm_gpiod_get_optional(dev, "enable", GPIOD_OUT_LOW);
> +       if (IS_ERR(platform->pdata.gpio_p_on)) {
> +               DRM_DEV_DEBUG_DRIVER(dev, "no enable gpio found\n");
> +               platform->pdata.gpio_p_on = NULL;
> +       }
> +
>         /* Gpio for chip reset */
>         platform->pdata.gpio_reset =
>                 devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
> +       if (IS_ERR(platform->pdata.gpio_reset)) {
> +               DRM_DEV_DEBUG_DRIVER(dev, "no reset gpio found\n");
> +               platform->pdata.gpio_p_on = NULL;
> +       }
>
>         if (platform->pdata.gpio_p_on && platform->pdata.gpio_reset) {
>                 platform->pdata.low_power_mode = 1;

devm_gpiod_get_optional() is possible to return NULL (see
https://elixir.bootlin.com/linux/v5.15.2/source/drivers/gpio/gpiolib-devres.c#L250).
Thus, we should use IS_ERR_OR_NULL for checking the return value.

The cases here would work fine except it will skip to print some
informative messages.

Acked-by: Tzung-Bi Shih <tzungbi@...gle.com>