linux-kernel - Re: [PATCH v8 05/18] drm/bridge: Move legacy bridge driver out of imx directory for multi-platform use

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Message-ID: <8c305f74-7fa7-4798-b1b3-e96544d962a1@rock-chips.com>
Date: Wed, 4 Feb 2026 09:09:07 +0800
From: Damon Ding <damon.ding@...k-chips.com>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>, andrzej.hajda@...el.com,
 neil.armstrong@...aro.org, rfoss@...nel.org,
 dmitry.baryshkov@....qualcomm.com
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, 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 05/18] drm/bridge: Move legacy bridge driver out of imx
 directory for multi-platform use

Hi Luca,

On 2/3/2026 6:11 PM, Luca Ceresoli wrote:
> Hello Damon,
> 
> On Tue Feb 3, 2026 at 2:31 AM CET, Damon Ding wrote:
>> Hi,
>>
>> On 2/2/2026 10:54 AM, Damon Ding wrote:
>>> Hi Luca,
>>>
>>> On 1/31/2026 8:33 PM, Luca Ceresoli wrote:
>>>> Hello Damon, Dmitry,
>>>>
>>>> On Wed Dec 17, 2025 at 10:33 AM CET, Damon Ding wrote:
>>>>> As suggested by Dmitry, the DRM legacy bridge driver can be pulled
>>>>> out of imx/ subdir for multi-platform use. The driver is also renamed
>>>>> to make it more generic and suitable for platforms other than i.MX.
>>>>>
>>>>> Signed-off-by: Damon Ding <damon.ding@...k-chips.com>
>>>>> Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
>>>>> Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
>>>>>
>>>>> ---
>>>>>
>>>>> Changes in v7:
>>>>> - Rename legacy-bridge to of-display-mode-bridge.
>>>>> - Remove unnecessary API drm_bridge_is_legacy().
>>>>
>>>> ...
>>>>
>>>>> --- a/drivers/gpu/drm/bridge/Kconfig
>>>>> +++ b/drivers/gpu/drm/bridge/Kconfig
>>>>> @@ -244,6 +244,16 @@ config DRM_NXP_PTN3460
>>>>>        help
>>>>>          NXP PTN3460 eDP-LVDS bridge chip driver.
>>>>>
>>>>> +config DRM_OF_DISPLAY_MODE_BRIDGE
>>>>> +    tristate
>>>>> +    depends on DRM_BRIDGE && OF
>>>>> +    help
>>>>> +      This is a DRM bridge implementation that uses
>>>>> of_get_drm_display_mode
>>>>> +      to acquire display mode.
>>>>> +
>>>>> +      Newer designs should not use this bridge and should use proper
>>>>> panel
>>>>> +      driver instead.
>>>>
>>>> "Newer designs should not use this bridge", but in patch 8 you are
>>>> introducing a new use ot devm_drm_of_display_mode_bridge(). Shouldn't you
>>>> instead "use proper panel driver instead" in patch 8?
>>>>
>>>> Can you point to the conversation where the converstaion where Dmitry
>>>> suggested this change? Maybe it already contains the answer to my
>>>> qustion. Also adding a link to that conversation in the commit message
>>>> woule be useful.
>>>>
>>>
>>> First of all, thanks for your reviews on this patch series.
>>>
>>> link: https://lore.kernel.org/all/
>>> xwenycscalzdlpuxytorbiyvej3k7pv3lhxwtadilxq65ipwsv@...xm53w5e22/
>>>
>>> I think it may be a misleading issue caused by directly copying the
>>> previous Kconfig description. Now that the new
>>> devm_drm_of_display_mode_bridge() helper has been added, drivers using
>>> the panel-bridge framework can rely on it to maintain compatibility with
>>> legacy display mode parsing.
> 
> Ah, I think I got the point: the mode description in device tree is legacy,
> but the driver itself is not legacy and will be current until we need to
> support legacy device tree. Correct?
> 
> If that's correct, this patch looks OK to me with a new Kconfig help text.

Right. I want to apply the advanced panel-bridge framework for Exynos DP 
driver, and this newly added API helps handle the legacy device tree 
that it supports.

The v9 will come soon.

> 
>>> It would be better to update the comment as follows:
>>>
>>> This is a DRM bridge implementation that uses of_get_drm_display_mode to
>>> acquire display mode.
>>>
>>> It exists for compatibility with legacy display mode parsing, in order
>>> to conform to the panel-bridge framework.
>>>
>>
>> Dmitry, what's you take on this?
> 
> Dmitry's opinion would be much more relevant than mine. I don't know much
> myself about this driver.
> 

Best regards,
Damon