linux-kernel - Re: [PATCH v9 0/6] MHDP8546 fixes related to DBANC usecase

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Message-ID: <i7byagpaadjjhc6rbqvejsxezn2eeomtw2ddpxirwjuezfdf3x@tez2ooxn76dv>
Date: Tue, 18 Nov 2025 13:40:36 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Harikrishna Shenoy <h-shenoy@...com>
Cc: Laurent.pinchart@...asonboard.com, airlied@...il.com, 
	andrzej.hajda@...el.com, andy.yan@...k-chips.com, aradhya.bhatia@...ux.dev, 
	devarsht@...com, dianders@...omium.org, dri-devel@...ts.freedesktop.org, 
	javierm@...hat.com, jernej.skrabec@...il.com, jonas@...boo.se, 
	linux-kernel@...r.kernel.org, linux@...blig.org, luca.ceresoli@...tlin.com, lumag@...nel.org, 
	lyude@...hat.com, maarten.lankhorst@...ux.intel.com, mordan@...ras.ru, 
	neil.armstrong@...aro.org, rfoss@...nel.org, s-jain1@...com, simona@...ll.ch, 
	tomi.valkeinen@...asonboard.com, tzimmermann@...e.de, u-kumar1@...com
Subject: Re: [PATCH v9 0/6]  MHDP8546 fixes related to DBANC usecase

Hi,

On Tue, Nov 18, 2025 at 05:22:49PM +0530, Harikrishna Shenoy wrote:
> With the DBANC framework, the connector is no longer initialized in 
> bridge_attach() when the display controller sets the 
> DRM_BRIDGE_ATTACH_NO_CONNECTOR flag. 
> This causes a null pointer dereference in cdns_mhdp_modeset_retry_fn() 
> when trying to access &conn->dev->mode_config.mutex. 
> Observed on a board where EDID read failed. 
> (log: https://gist.github.com/Jayesh2000/233f87f9becdf1e66f1da6fd53f77429)
> 
> Patch 1 adds a connector_ptr which takes care of both 
> DBANC and !DBANC case by setting the pointer in appropriate hooks
> and checking for pointer validity before accessing the connector.
> Patch 2 adds mode validation hook to bridge fucntions.
> Patch 3 fixes HDCP to work with both DBANC and !DBANC case by
> moving HDCP state handling into the bridge atomic check in line with 
> the DBANC model.
> Patches 4,5 do necessary cleanup and alignment for using
> connector pointer.

It's mentioned several times in your series, and it might be obvious to
you, but documenting what is the "DBANC framework" is would be helpful.
I have no idea what it's about, and it appears that Google doesn't know
either.

Maxime

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