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

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Message-Id: <DFE1K6AD151E.23NWWMYDV2ZDI@bootlin.com>
Date: Fri, 02 Jan 2026 11:46:08 +0100
From: "Luca Ceresoli" <luca.ceresoli@...tlin.com>
To: "Osama Abdelkader" <osama.abdelkader@...il.com>, "Andy Yan"
 <andy.yan@...k-chips.com>
Cc: <stable@...r.kernel.org>, "Andrzej Hajda" <andrzej.hajda@...el.com>,
 "Neil Armstrong" <neil.armstrong@...aro.org>, "Robert Foss"
 <rfoss@...nel.org>, "Laurent Pinchart" <Laurent.pinchart@...asonboard.com>,
 "Jonas Karlman" <jonas@...boo.se>, "Jernej Skrabec"
 <jernej.skrabec@...il.com>, "Maarten Lankhorst"
 <maarten.lankhorst@...ux.intel.com>, "Maxime Ripard" <mripard@...nel.org>,
 "Thomas Zimmermann" <tzimmermann@...e.de>, "David Airlie"
 <airlied@...il.com>, "Simona Vetter" <simona@...ll.ch>, "Dmitry Baryshkov"
 <dmitry.baryshkov@....qualcomm.com>, <dri-devel@...ts.freedesktop.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drm/bridge: synopsys: dw-dp: return when attach
 bridge fail

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@...r.kernel.org
>
> Signed-off-by: Osama Abdelkader <osama.abdelkader@...il.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