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

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Message-ID: <20211118054346.GA3796880@anxtwsw-Precision-3640-Tower>
Date:   Thu, 18 Nov 2021 13:43:46 +0800
From:   Xin Ji <xji@...logixsemi.com>
To:     Tzung-Bi Shih <tzungbi@...gle.com>
Cc:     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 12:52:14PM +0800, Tzung-Bi Shih wrote:
> 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://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Felixir.bootlin.com%2Flinux%2Fv5.15.2%2Fsource%2Fdrivers%2Fgpio%2Fgpiolib-devres.c%23L250&amp;data=04%7C01%7Cxji%40analogixsemi.com%7C40e84a44676149c2544a08d9aa4f37f0%7Cb099b0b4f26c4cf59a0fd5be9acab205%7C0%7C0%7C637728079481953910%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=2UPuAadtM%2FObwkwE6fLhJr7uCfWN%2Fr29o4t8uqUU2Ls%3D&amp;reserved=0).
> Thus, we should use IS_ERR_OR_NULL for checking the return value.
Hi Tzung-Bi Shih, IS_ERR_OR_NULL is better, I'll use it.

Thanks,
Xin
> 
> The cases here would work fine except it will skip to print some
> informative messages.
> 
> Acked-by: Tzung-Bi Shih <tzungbi@...gle.com>