[PATCH] drm/bridge: anx7625: Check GPIO description to avoid crash

[PATCH] drm/bridge: anx7625: Check GPIO description to avoid crash

[Xin Ji]

As GPIO probe function "devm_gpiod_get_optional()" may return error
code, driver should identify GPIO desc as NULL to avoid crash.

Signed-off-by: Xin Ji <xji@analogixsemi.com>
---
 drivers/gpu/drm/bridge/analogix/anx7625.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c
index 001fb39d9919..36e0ae5a1c7b 100644
--- a/drivers/gpu/drm/bridge/analogix/anx7625.c
+++ b/drivers/gpu/drm/bridge/analogix/anx7625.c
@@ -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;
-- 
2.25.1

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

[Tzung-Bi Shih]

On Thu, Nov 18, 2021 at 11:11 AM Xin Ji <xji@analogixsemi.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@google.com>

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

[Xin Ji]

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@analogixsemi.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@google.com>