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

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Message-ID: <aVfrDJojCylccwYJ@osama>
Date: Fri, 2 Jan 2026 16:58:04 +0100
From: Osama Abdelkader <osama.abdelkader@...il.com>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>
Cc: Andy Yan <andy.yan@...k-chips.com>, 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

On Fri, Jan 02, 2026 at 11:46:08AM +0100, Luca Ceresoli wrote:
> 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?

Thanks Luca for the review, I just sent v3.

Best regards,
Osama

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