Re: [PATCH v3] drm/ingenic: fix bridge allocation

[Paul Cercueil]

Hi Nikolaus,

Le dimanche 23 août 2026 à 16:12 +0200, H. Nikolaus Schaller a écrit :
> Bridge allocation API has changed and ingenic/drm was broken
> leading to
> 
> [   54.997593] dw-hdmi-ingenic 10180000.hdmi: Detected HDMI \X
> controller v1.31a with HDCP (DWC HDMI 3D TX PHY)
> [   55.491338] dw-hdmi-ingenic 10180000.hdmi: registered DesignWare
> HDMI I2C bus driver
> [   55.899132] [drm] DRM bridge corrupted or not allocated by
> devm_drm_bridge_alloc()
> [   55.904136] ------------[ cut here ]------------
> [   55.908753] WARNING: lib/refcount.c:25 at drm_bridge_get+0x58/0x6c
> [drm], CPU#0: kworker/u4:2/36
> [   55.917538] refcount_t: addition on 0; use-after-free.
> ...
> [   56.354928] [<c04898b8>] drm_bridge_attach+0x80/0x208 [drm]
> ...
> 
> Fixes: 9347f2fbb0183b0 ("drm/bridge: add warning for bridges using
> neither devm_drm_bridge_alloc() nor drm_bridge_add()")
> Tested-by: Waldemar Brodkorb <wbx@xxxxxxxxxxx> (on CI20 with HDMI)
> Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
> Cc: Waldemar Brodkorb <wbx@xxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> 
> Notes:
>     v3: fixed a malformed diff
>     
>     v2: removed ib->bridge->ops = DRM_BRIDGE_OP_EDID |
> DRM_BRIDGE_OP_DETECT as suggested by Sashiko-reviews
>        
> https://sashiko.dev/#/patchset/400ba2fe0d4f76484e929d2efaa32f67a940163a.1787477392.git.hns@xxxxxxxxxxxxx?part=1
> 
>  drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 23 +++++++++++++++++++--
> --
>  1 file changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> index 42c86f195c66b3..8d7979a7859332 100644
> --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> @@ -122,7 +122,7 @@ struct ingenic_drm {
>  
>  struct ingenic_drm_bridge {
>  	struct drm_encoder encoder;
> -	struct drm_bridge bridge, *next_bridge;
> +	struct drm_bridge *bridge, *next_bridge;
>  
>  	struct drm_bus_cfg bus_cfg;
>  };
> @@ -802,7 +802,7 @@ static int ingenic_drm_bridge_attach(struct
> drm_bridge *bridge,
>  	struct ingenic_drm_bridge *ib =
> to_ingenic_drm_bridge(encoder);
>  
>  	return drm_bridge_attach(encoder, ib->next_bridge,
> -				 &ib->bridge, flags);
> +				 bridge, flags);
>  }
>  
>  static int ingenic_drm_bridge_atomic_check(struct drm_bridge
> *bridge,
> @@ -1314,10 +1314,25 @@ static int ingenic_drm_bind(struct device
> *dev, bool has_components)
>  
>  		drm_encoder_helper_add(encoder,
> &ingenic_drm_encoder_helper_funcs);
>  
> -		ib->bridge.funcs = &ingenic_drm_bridge_funcs;
> +		ib->bridge = devm_drm_bridge_alloc(priv->dev, struct
> drm_bridge,
> +						   base,
> &ingenic_drm_bridge_funcs);
> +		if (IS_ERR(ib->bridge)) {
> +			ret = PTR_ERR(ib->bridge);
> +			goto err_drvdata;
> +		}
> +
> +		ib->bridge->of_node = priv->dev->of_node;
>  		ib->next_bridge = bridge;
>  
> -		ret = drm_bridge_attach(encoder, &ib->bridge, NULL,
> +		ib->bridge->interlace_allowed = true;

That one line feels like it doesn't belong here, but in its own patch.

Cheers,
-Paul

> +
> +		ret = devm_drm_bridge_add(priv->dev, ib->bridge);
> +		if (ret) {
> +			dev_err(dev, "Failed to register DRM bridge:
> %d\n", ret);
> +			goto err_drvdata;
> +		}
> +
> +		ret = drm_bridge_attach(encoder, ib->bridge, NULL,
>  					DRM_BRIDGE_ATTACH_NO_CONNECT
> OR);
>  		if (ret) {
>  			dev_err(dev, "Unable to attach bridge\n");