Re: [PATCH v2] drm/bridge: synopsys: dw-dp: return when attach bridge fail

["Luca Ceresoli" <luca.ceresoli@bootlin.com>]

Hello Osama, Andy Yan,

Andy, a question for you below.

On Wed Dec 31, 2025 at 3:41 PM CET, Osama Abdelkader wrote:
> When drm_bridge_attach() fails, the function should return an error
> instead of continuing execution.
>
> Fixes: 86eecc3a9c2e ("drm/bridge: synopsys: Add DW DPTX Controller support library")
> Cc: stable@vger.kernel.org
>
> Signed-off-by: Osama Abdelkader <osama.abdelkader@gmail.com>
> ---
> v2:
> use concise error message
> add Fixes and Cc tags
> ---
>  drivers/gpu/drm/bridge/synopsys/dw-dp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-dp.c b/drivers/gpu/drm/bridge/synopsys/dw-dp.c
> index 82aaf74e1bc0..bc311a596dff 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-dp.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-dp.c
> @@ -2063,7 +2063,7 @@ struct dw_dp *dw_dp_bind(struct device *dev, struct drm_encoder *encoder,
>
>  	ret = drm_bridge_attach(encoder, bridge, NULL, DRM_BRIDGE_ATTACH_NO_CONNECTOR);
>  	if (ret)
> -		dev_err_probe(dev, ret, "Failed to attach bridge\n");
> +		return ERR_PTR(dev_err_probe(dev, ret, "Failed to attach bridge\n"));

Your change looks good now. However there is aanother issue, sorry for not
having noticed before.

While reading the dw_dp_bind() code in its entirety I have noticed that on
any error after drm_bridge_attach() (and also a drm_bridge_attach() error,
with this patch) it returns without undoing the previous actions. This is
fine for devm actions, but a problem for non-devm actions, which start at
drm_dp_aux_register().

For example, if phy_init() fails, dw_dp_bind() returns without calling
drm_dp_aux_unregister(), thus leaking the resources previously allocated by
drm_dp_aux_register().

Andy, can you tell whether my analysis is correct?

If it is, this should be fixed before applying this patch. Osama, do you
think you can add such a patch in your next iteration?

Best regards,
Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com