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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <22985633-f20c-4f36-96d1-ce01fe6cf6df@ideasonboard.com>
Date: Fri, 21 Nov 2025 14:07:36 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
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, mripard@...nel.org, neil.armstrong@...aro.org,
 rfoss@...nel.org, s-jain1@...com, simona@...ll.ch, tzimmermann@...e.de,
 u-kumar1@...com
Subject: Re: [PATCH RESEND v9 0/6] MHDP8546 fixes related to
 DRM_BRIDGE_ATTACH_NO_CONNECTOR usecase

Hi,

On 20/11/2025 14:14, Harikrishna Shenoy wrote:
> With the DRM_BRIDGE_ATTACH_NO_CONNECTOR 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 
> DRM_BRIDGE_ATTACH_NO_CONNECTOR and !DRM_BRIDGE_ATTACH_NO_CONNECTOR 
> 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 DRM_BRIDGE_ATTACH_NO_CONNECTOR 
> and !DRM_BRIDGE_ATTACH_NO_CONNECTOR case by moving HDCP state handling 
> into the bridge atomic check inline with the 
> DRM_BRIDGE_ATTACH_NO_CONNECTOR model.
> Patches 4,5 do necessary cleanup and alignment for using
> connector pointer.
> 
> The rationale behind the sequence of commits is we can cleanly 
> switch to drm_connector pointer after removal of connector helper 
> code blocks, which are anyways not touch after 
> DRM_BRIDGE_ATTACH_NO_CONNECTOR has been enabled in driver.
> 
> The last patch make smaller adjustment: lowering the log level for
> noisy DPCD transfer errors.
> 
> v8 patch link:
> <https://lore.kernel.org/all/20251014094527.3916421-1-h-shenoy@ti.com/>
> 
> Changelog v8-v9:
> -Move the patch 6 in v8 related to HDCP to patch 3 and add fixes tag.
> -Update to connector_ptr in HDCP code in patch 1.
> -Rebased on next-20251114.

Don't base on linux-next, except in some quite special circumstances.
Base on latest major version from Linus, or -rc from Linus, or
drm-misc-next. Usually drm-misc-next is a safe choice for DRM patches.

And if you make changes to a series, it's not a "resend" but a new version.

 Tomi

> 
> v7 patch link:
> <https://lore.kernel.org/all/20250929083936.1575685-1-h-shenoy@ti.com/>
> 
> Changelog v7-v8:
> -Move patches with firxes tag to top of series with appropriate changes
> to them.
> -Add R/B tag to patch 
> https://lore.kernel.org/all/ae3snoap64r252sbqhsshsadxfmlqdfn6b4o5fgfcmxppglkqf@2lsstfsghzwb/
> 
> v6 patch link:
> <https://lore.kernel.org/all/20250909090824.1655537-1-h-shenoy@ti.com/>
> 
> Changelog v6-v7:
> -Update cover letter to explain the series.
> -Add R/B tag in PATCH 1 and drop fixes tag as suggested.
> -Drop fixes tag in PATCH 2.
> -Update the commit messages for clear understanding of changes done in patches.
> 
> v5 patch link:
> <https://lore.kernel.org/all/20250811075904.1613519-1-h-shenoy@ti.com/>
> 
> Changelog v5 -> v6:
> -Update cover letter to clarify the series in better way.
> -Add Reviewed-by tag to relevant patches.
>  
> v4 patch link: 
> <https://lore.kernel.org/all/20250624054448.192801-1-j-choudhary@ti.com>
> 
> Changelog v4->v5:
> - Handle HDCP state in bridge atomic check instead of connector 
> atomic check
>  
> v3 patch link:
> <https://lore.kernel.org/all/20250529142517.188786-1-j-choudhary@ti.com/>
> 
> Changelog v3->v4:
> - Fix kernel test robot build warning:
>   <https://lore.kernel.org/all/202505300201.2s6r12yc-lkp@intel.com/>
> 
> v2 patch link:
> <https://lore.kernel.org/all/20250521073237.366463-1-j-choudhary@ti.com/>
> 
> Changelog v2->v3:
> - Add mode_valid in drm_bridge_funcs to a separate patch
> - Remove "if (mhdp->connector.dev)" conditions that were missed in v2
> - Split out the move of drm_atomic_get_new_connector_for_encoder()
>   to a separate patch
> - Drop "R-by" considering the changes in v2[1/3]
> - Add Fixes tag to first 4 patches:
>   commit c932ced6b585 ("drm/tidss: Update encoder/bridge chain connect model")
>   This added DBANC flag in tidss while attaching bridge to the encoder
> - Drop RFC prefix
> 
> v1 patch link:
> <https://lore.kernel.org/all/20250116111636.157641-1-j-choudhary@ti.com/>
> 
> Changelog v1->v2:
> - Remove !DRM_BRIDGE_ATTACH_NO_CONNECTOR entirely
> - Add mode_valid in drm_bridge_funcs[0]
> - Fix NULL POINTER differently since we cannot access atomic_state
> - Reduce log level in cdns_mhdp_transfer call
> 
> [0]: https://lore.kernel.org/all/20240530091757.433106-1-j-choudhary@ti.com/
> 
> Harikrishna Shenoy (1):
>   drm/bridge: cadence: cdns-mhdp8546-core: Handle HDCP state in bridge
>     atomic check
> 
> Jayesh Choudhary (5):
>   drm/bridge: cadence: cdns-mhdp8546-core: Set the mhdp connector
>     earlier in atomic_enable()
>   drm/bridge: cadence: cdns-mhdp8546-core: Add mode_valid hook to
>     drm_bridge_funcs
>   drm/bridge: cadence: cdns-mhdp8546-core: Remove legacy support for
>     connector initialisation in bridge
>   drm/bridge: cadence: cdns-mhdp8546*: Change drm_connector from
>     structure to pointer
>   drm/bridge: cadence: cdns-mhdp8546-core: Reduce log level for DPCD
>     read/write
> 
>  .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 258 +++++-------------
>  .../drm/bridge/cadence/cdns-mhdp8546-core.h   |   2 +-
>  .../drm/bridge/cadence/cdns-mhdp8546-hdcp.c   |   8 +-
>  3 files changed, 72 insertions(+), 196 deletions(-)
>