Re: [PATCH] drm/bridge: anx7625: Zero error variable when panel bridge not present

[José Expósito]

On Mon, Jun 13, 2022 at 12:37:05PM -0400, Nícolas F. R. A. Prado wrote:
> While parsing the DT, the anx7625 driver checks for the presence of a
> panel bridge on endpoint 1. If it is missing, pdata->panel_bridge stores
> the error pointer and the function returns successfully without first
> cleaning that variable. This is an issue since other functions later
> check for the presence of a panel bridge by testing the trueness of that
> variable.
> 
> In order to ensure proper behavior, zero out pdata->panel_bridge before
> returning when no panel bridge is found.
> 
> Fixes: 9e82ea0fb1df ("drm/bridge: anx7625: switch to devm_drm_of_get_bridge")
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@xxxxxxxxxxxxx>
> 
> ---
> 
>  drivers/gpu/drm/bridge/analogix/anx7625.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c
> index 53a5da6c49dd..3aed4de16690 100644
> --- a/drivers/gpu/drm/bridge/analogix/anx7625.c
> +++ b/drivers/gpu/drm/bridge/analogix/anx7625.c
> @@ -1657,8 +1657,10 @@ static int anx7625_parse_dt(struct device *dev,
>  
>  	pdata->panel_bridge = devm_drm_of_get_bridge(dev, np, 1, 0);
>  	if (IS_ERR(pdata->panel_bridge)) {
> -		if (PTR_ERR(pdata->panel_bridge) == -ENODEV)
> +		if (PTR_ERR(pdata->panel_bridge) == -ENODEV) {
> +			pdata->panel_bridge = NULL;
>  			return 0;
> +		}
>  
>  		return PTR_ERR(pdata->panel_bridge);
>  	}
> -- 
> 2.36.1
> 

Thanks for spotting this error Nícolas. As you mentioned, prior to
9e82ea0fb1df the "pdata->panel_bridge" pointer was not modified
(i.e. left to NULL) on the ENODEV error branch.

I missed it during the refactor, sorry about that.