[PATCH v4] drm/bridge: display-connector: implement the error path of .probe()

[Laurent Pinchart]

Hi Joe,

Thank you for the patch.

On Fri, Jan 31, 2025 at 04:34:53PM +0900, Joe Hattori wrote:
> Current implementation of .probe() leaks a reference of i2c_adapter.
> Implement an error path and call put_device() on the obtained
> i2c_adapter in it to fix this refcount bug.
> 
> Also, remove the IS_ERR() check before calling
> i2c_put_adapter(conn->bridge.ddc) since conn->bridge.dcc is either NULL
> or a valid pointer, and a null-check is already done in
> i2c_put_adapter().
> 
> This bug was found by an experimental verification tool that I am
> developing.
> 
> Fixes: 0c275c30176b ("drm/bridge: Add bridge driver for display connectors")
> Signed-off-by: Joe Hattori <joe at pf.is.s.u-tokyo.ac.jp>
> ---
> Changes in V4:
> - Stopped assigning the return value of dev_err_probe().
> - Updated the commit message.
> 
> Changes in V3:
> - Removed shadowed variables (ret).
> 
> Changes in V2:
> - Omit the null check before calling i2c_put_adapter().
> ---
>  drivers/gpu/drm/bridge/display-connector.c | 31 +++++++++++++---------
>  1 file changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/display-connector.c b/drivers/gpu/drm/bridge/display-connector.c
> index 72bc508d4e6e..52a86f99fa45 100644
> --- a/drivers/gpu/drm/bridge/display-connector.c
> +++ b/drivers/gpu/drm/bridge/display-connector.c
> @@ -329,35 +329,39 @@ static int display_connector_probe(struct platform_device *pdev)
>  
>  	/* Get the DP PWR for DP connector. */
>  	if (type == DRM_MODE_CONNECTOR_DisplayPort) {
> -		int ret;
> -
>  		ret = display_connector_get_supply(pdev, conn, "dp-pwr");
> -		if (ret < 0)
> -			return dev_err_probe(&pdev->dev, ret, "failed to get DP PWR regulator\n");
> +		if (ret < 0) {
> +			dev_err_probe(&pdev->dev, ret,
> +					    "failed to get DP PWR regulator\n");
> +			goto err_put;
> +		}
>  	}
>  
>  	/* enable DDC */
>  	if (type == DRM_MODE_CONNECTOR_HDMIA) {
> -		int ret;
> -
>  		conn->ddc_en = devm_gpiod_get_optional(&pdev->dev, "ddc-en",
>  						       GPIOD_OUT_HIGH);
>  
>  		if (IS_ERR(conn->ddc_en)) {
>  			dev_err(&pdev->dev, "Couldn't get ddc-en gpio\n");
> -			return PTR_ERR(conn->ddc_en);
> +			ret = PTR_ERR(conn->ddc_en);
> +			goto err_put;
>  		}
>  
>  		ret = display_connector_get_supply(pdev, conn, "hdmi-pwr");
> -		if (ret < 0)
> -			return dev_err_probe(&pdev->dev, ret, "failed to get HDMI +5V Power regulator\n");
> +		if (ret < 0) {
> +			dev_err_probe(
> +				&pdev->dev, ret,
> +				"failed to get HDMI +5V Power regulator\n");

This looks weird.

			dev_err_probe(&pdev->dev, ret,
				      "failed to get HDMI +5V Power regulator\n");

or

			dev_err_probe(&pdev->dev, ret, "failed to get HDMI +5V Power regulator\n");
if you prefer.

With that fixed,

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

> +			goto err_put;
> +		}
>  	}
>  
>  	if (conn->supply) {
>  		ret = regulator_enable(conn->supply);
>  		if (ret) {
>  			dev_err(&pdev->dev, "failed to enable PWR regulator: %d\n", ret);
> -			return ret;
> +			goto err_put;
>  		}
>  	}
>  
> @@ -383,6 +387,10 @@ static int display_connector_probe(struct platform_device *pdev)
>  	drm_bridge_add(&conn->bridge);
>  
>  	return 0;
> +
> +err_put:
> +	i2c_put_adapter(conn->bridge.ddc);
> +	return ret;
>  }
>  
>  static void display_connector_remove(struct platform_device *pdev)
> @@ -397,8 +405,7 @@ static void display_connector_remove(struct platform_device *pdev)
>  
>  	drm_bridge_remove(&conn->bridge);
>  
> -	if (!IS_ERR(conn->bridge.ddc))
> -		i2c_put_adapter(conn->bridge.ddc);
> +	i2c_put_adapter(conn->bridge.ddc);
>  }
>  
>  static const struct of_device_id display_connector_match[] = {

-- 
Regards,

Laurent Pinchart