Message-ID: <7d937ad1-dd7c-4a68-9af7-f386ca2c27dc@nxp.com>
Date: Fri, 9 Jan 2026 17:53:17 +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>,
 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 v4 0/4] drm/bridge: add of_drm_find_and_get_bridge() and a
 managed *next_bridge, deprecate of_drm_find_bridge()



On 1/7/26 17:56, Luca Ceresoli wrote:
> This v4 contains the leftovers of the v3 series that deprecated
> of_drm_find_bridge(), added a replacement which handles bridge refcounting,
> and converted some of the direct users. All patches have been applied
> except the imx8qxp-pixel-link ones, which still need a review for the first
> patch.
> 
> @Liu, patch 1 is waiting for a review and it's non-trivial, it would be
> nice if you could have a look at that one at least.

Luca, I'v been too busy recently for tasks assigned by my employer to
give an in-time review, sorry about that.  I'll try to review this late
next week if not sooner.

> 
> This is part of the work to support hotplug of DRM bridges. The grand plan
> was discussed in [0].
> 
> Here's the work breakdown (➜ marks the current series):
> 
>  1. ➜ add refcounting to DRM bridges struct drm_bridge,
>       based on devm_drm_bridge_alloc()
>     A. ✔ add new alloc API and refcounting (v6.16)
>     B. ✔ convert all bridge drivers to new API (v6.17)
>     C. ✔ kunit tests (v6.17)
>     D. ✔ add get/put to drm_bridge_add/remove() + attach/detach()
>          and warn on old allocation pattern (v6.17)
>     E. ➜ add get/put on drm_bridge accessors
>        1. ✔ drm_bridge_chain_get_first_bridge(), add cleanup action (v6.18)
>        2. ✔ drm_bridge_get_prev_bridge() (v6.18)
>        3. ✔ drm_bridge_get_next_bridge() (v6.19)
>        4. ✔ drm_for_each_bridge_in_chain() (v6.19)
>        5. ✔ drm_bridge_connector_init (v6.19)
>        6. … protect encoder bridge chain with a mutex
>        7. ➜ of_drm_find_bridge()
>           a. ➜✔… add of_drm_get_bridge(), convert basic direct users
> 	         (v6.20?, one driver still pending)
> 	  b. convert other direct users
> 	  c. convert bridge-only drm_of_find_panel_or_bridge() users
>        8. drm_of_find_panel_or_bridge, *_of_get_bridge
>        9. ✔ enforce drm_bridge_add before drm_bridge_attach (v6.19)
>     F. ✔ debugfs improvements
>        1. ✔ add top-level 'bridges' file (v6.16)
>        2. ✔ show refcount and list lingering bridges (v6.19)
>  2. … handle gracefully atomic updates during bridge removal
>     A. ✔ Add drm_dev_enter/exit() to protect device resources (v6.20?)
>     B. … protect private_obj removal from list
>  3. … DSI host-device driver interaction
>  4. ✔ removing the need for the "always-disconnected" connector
>  5. finish the hotplug bridge work, moving code to the core and potentially
>     removing the hotplug-bridge itself (this needs to be clarified as
>     points 1-3 are developed)
> 
> [0] https://lore.kernel.org/lkml/20250206-hotplug-drm-bridge-v6-0-9d6f2c9c3058@bootlin.com/#t
> 
> Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
> ---
> Changes in v4:
> - Added review trailers
> - Link to v3: https://lore.kernel.org/r/20251216-drm-bridge-alloc-getput-drm_of_find_bridge-v3-0-b5165fab8058@bootlin.com
> 
> Changes in v3:
> - Completely rewrote using the __drm_bridge_free() idea to prevent
>   use-after-free of the next_bridge for the common cases
> - Added needed cleanups to the imx8qxp-pixel-link and imx8qxp-pxl2dpi
>   drivers
> - Removed various patches converting simple cases, to reduce the number of
>   e-mails sent; will be moved to the follow-up series
> - Link to v2: https://lore.kernel.org/r/20251128-drm-bridge-alloc-getput-drm_of_find_bridge-v2-0-88f8a107eca2@bootlin.com
> 
> Changes in v2:
> - All patches: renamed drm_of_find_bridge() -> of_drm_get_bridge()
> - Various fixes and improvements to patches 1-6, see individual patches
>   changelog
> - Removed bouncing recipient: Edmund Dea <edmund.j.dea@...el.com>
> - Link to v1: https://lore.kernel.org/r/20251119-drm-bridge-alloc-getput-drm_of_find_bridge-v1-0-0db98a7fe474@bootlin.com
> 
> ---
> Luca Ceresoli (4):
>       drm/bridge: imx8qxp-pixel-link: simplify logic to find next bridge
>       drm/bridge: imx8qxp-pixel-link: simplify freeing of the remote device_node
>       drm/bridge: imx8qxp-pixel-link: imx8qxp_pixel_link_find_next_bridge: return int, not ERR_PTR
>       drm/bridge: imx8qxp-pixel-link: get/put the next bridge
> 
>  drivers/gpu/drm/bridge/imx/imx8qxp-pixel-link.c | 53 ++++++++++++-------------
>  1 file changed, 25 insertions(+), 28 deletions(-)
> ---
> base-commit: f12ad2e5233a1a30b3bd6fe1e784b3544caa2383
> change-id: 20251117-drm-bridge-alloc-getput-drm_of_find_bridge-74903367448d
> 
> Best regards,

-- 
Regards,
Liu Ying

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