linux-kernel - Re: [PATCH v8 04/18] drm/bridge: analogix_dp: Add &analogix_dp_plat_data.next

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Message-Id: <DFCCU8AN0GZQ.2CYTKKV40JYLI@bootlin.com>
Date: Wed, 31 Dec 2025 12:11:08 +0100
From: "Luca Ceresoli" <luca.ceresoli@...tlin.com>
To: "Damon Ding" <damon.ding@...k-chips.com>, <andrzej.hajda@...el.com>,
 <neil.armstrong@...aro.org>, <rfoss@...nel.org>
Cc: <Laurent.pinchart@...asonboard.com>, <jonas@...boo.se>,
 <jernej.skrabec@...il.com>, <maarten.lankhorst@...ux.intel.com>,
 <mripard@...nel.org>, <tzimmermann@...e.de>, <airlied@...il.com>,
 <simona@...ll.ch>, <shawnguo@...nel.org>, <s.hauer@...gutronix.de>,
 <kernel@...gutronix.de>, <festevam@...il.com>, <inki.dae@...sung.com>,
 <sw0312.kim@...sung.com>, <kyungmin.park@...sung.com>, <krzk@...nel.org>,
 <alim.akhtar@...sung.com>, <jingoohan1@...il.com>,
 <p.zabel@...gutronix.de>, <hjc@...k-chips.com>, <heiko@...ech.de>,
 <andy.yan@...k-chips.com>, <dmitry.baryshkov@....qualcomm.com>,
 <dianders@...omium.org>, <m.szyprowski@...sung.com>,
 <jani.nikula@...el.com>, <linux-kernel@...r.kernel.org>,
 <dri-devel@...ts.freedesktop.org>, <imx@...ts.linux.dev>,
 <linux-arm-kernel@...ts.infradead.org>,
 <linux-samsung-soc@...r.kernel.org>, <linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH v8 04/18] drm/bridge: analogix_dp: Add
 &analogix_dp_plat_data.next_bridge

Hello Damon,

On Wed Dec 17, 2025 at 10:33 AM CET, Damon Ding wrote:
> In order to move the panel/bridge parsing and attachmenet to the
> Analogix side, add component struct drm_bridge *next_bridge to
> platform data struct analogix_dp_plat_data.
>
> The movement makes sense because the panel/bridge should logically
> be positioned behind the Analogix bridge in the display pipeline.
>
> Signed-off-by: Damon Ding <damon.ding@...k-chips.com>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
> Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
>
> ---
>
> Changes in v4:
> - Rename the &analogix_dp_plat_data.bridge to
>   &analogix_dp_plat_data.next_bridge
> ---
>  include/drm/bridge/analogix_dp.h | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/include/drm/bridge/analogix_dp.h b/include/drm/bridge/analogix_dp.h
> index cf17646c1310..582357c20640 100644
> --- a/include/drm/bridge/analogix_dp.h
> +++ b/include/drm/bridge/analogix_dp.h
> @@ -27,6 +27,7 @@ static inline bool is_rockchip(enum analogix_dp_devtype type)
>  struct analogix_dp_plat_data {
>  	enum analogix_dp_devtype dev_type;
>  	struct drm_panel *panel;
> +	struct drm_bridge *next_bridge;
>  	struct drm_encoder *encoder;
>  	struct drm_connector *connector;
>  	bool skip_connector;

It took a while to understand why you are adding the next_bridge pointer in
struct analogix_dp_plat_data instead of struct analogix_dp_device, where it
would be more natural. I found an answer in patch 16: with current code you
need to place next_bridge in struct analogix_dp_plat_data because it is
used by user drivers to attach, and those drivers have no access to struct
analogix_dp_device. However patch 16 (which looks a very good cleanup BTW)
next_bridge can be moved to struct analogix_dp_device.

So I'd suggest to move patch 16 before this one if it easily doable, so
that you can introduce next_bridge in struct analogix_dp_device from the
beginning. Should that be impossible, you can send a separate patch to move
next_bridge, after patch 16.

Best regards,
Luca

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