linux-kernel - Re: [PATCH for drm-misc-fixes] drm/bridge: imx8qxp-pixel-combiner: Fix bailout for imx8qxp_pc_bridge

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Message-ID: <c99dcae4-f5d2-4039-a562-866896d162da@nxp.com>
Date: Thu, 29 Jan 2026 11:49:02 +0800
From: Liu Ying <victor.liu@....com>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>,
 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>,
 Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>,
 Pengutronix Kernel Team <kernel@...gutronix.de>,
 Fabio Estevam <festevam@...il.com>
Cc: Hui Pu <Hui.Pu@...ealthcare.com>, Ian Ray <ian.ray@...ealthcare.com>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 dri-devel@...ts.freedesktop.org, imx@...ts.linux.dev,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH for drm-misc-fixes] drm/bridge: imx8qxp-pixel-combiner:
 Fix bailout for imx8qxp_pc_bridge_probe()



On Wed, Jan 28, 2026 at 06:55:09PM +0100, Luca Ceresoli wrote:
> In case the channel0 is unavailable and bailing out from free_child is
> needed when we fail to add a DRM bridge for the available channel1,
> pointer pc->ch[0] in the bailout path would be NULL and it would be
> dereferenced as pc->ch[0]->bridge.next_bridge.  Fix this by checking
> pc->ch[0] before dereferencing it.
> 
> Fixes: 99764593528f ("drm/bridge: imx8qxp-pixel-combiner: convert to devm_drm_bridge_alloc() API")
> Reported-by: Liu Ying <victor.liu@....com>
> Closes: https://lore.kernel.org/lkml/20260123-imx8qxp-drm-bridge-fixes-v1-3-8bb85ada5866@nxp.com/
> [Luca: backported on drm-misc-fixes where the original commit conflicts]
> Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
> ---
>  drivers/gpu/drm/bridge/imx/imx8qxp-pixel-combiner.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-combiner.c b/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-combiner.c
> index 8517b1c953d4..dc1cb094afd0 100644
> --- a/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-combiner.c
> +++ b/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-combiner.c
> @@ -349,7 +349,7 @@ static int imx8qxp_pc_bridge_probe(struct platform_device *pdev)
>  free_child:
>  	of_node_put(child);
>  
> -	if (i == 1 && pc->ch[0]->next_bridge)
> +	if (i == 1 && pc->ch[0] && pc->ch[0]->next_bridge)
>  		drm_bridge_remove(&pc->ch[0]->bridge);
>  
>  	pm_runtime_disable(dev);
> 

Tested-by: Liu Ying <victor.liu@....com>

I'm not sure if there is any proper process to handle conflict between
this patch and commit [1] in drm-misc-next.  If that's clear, I probably
add my R-b tag.

[1] commit ae754f049ce1 ("drm/bridge: imx8qxp-pixel-combiner: get/put the next bridge")

-- 
Regards,
Liu Ying