linux-kernel - Re: [PATCH 4/6] drm/mcde: dsi: convert to of_drm_find_and_get

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Message-Id: <DG2VP9N60DMK.30G4A13VNX7CA@bootlin.com>
Date: Sat, 31 Jan 2026 16:27:19 +0100
From: "Luca Ceresoli" <luca.ceresoli@...tlin.com>
To: "Linus Walleij" <linusw@...nel.org>
Cc: "Biju Das" <biju.das.jz@...renesas.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>, "Anitha
 Chrisanthus" <anitha.chrisanthus@...el.com>, "Edmund Dea"
 <edmund.j.dea@...el.com>, "Laurent Pinchart"
 <laurent.pinchart+renesas@...asonboard.com>, "Tomi Valkeinen"
 <tomi.valkeinen+renesas@...asonboard.com>, "Kieran Bingham"
 <kieran.bingham+renesas@...asonboard.com>, "Geert Uytterhoeven"
 <geert+renesas@...der.be>, "Magnus Damm" <magnus.damm@...il.com>, "Tomi
 Valkeinen" <tomi.valkeinen@...asonboard.com>, "Hui Pu"
 <Hui.Pu@...ealthcare.com>, "Ian Ray" <ian.ray@...ealthcare.com>, "Thomas
 Petazzoni" <thomas.petazzoni@...tlin.com>,
 <dri-devel@...ts.freedesktop.org>, <linux-renesas-soc@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/6] drm/mcde: dsi: convert to
 of_drm_find_and_get_bridge()

Hello Linus,

On Mon Jan 19, 2026 at 9:57 AM CET, Linus Walleij wrote:
> On Fri, Jan 16, 2026 at 6:33 PM Luca Ceresoli <luca.ceresoli@...tlin.com> wrote:
>
>> of_drm_find_bridge() is deprecated. Move to its replacement
>> of_drm_find_and_get_bridge() which gets a bridge reference, and ensure it
>> is put when done.
>>
>> We need to handle the two cases: when a panel is found and when it isn't,
>> even though the latter is not supported. So:
>>
>>  * in case a panel is not found and bridge is, get a reference to the
>>    found bridge
>>  * in case a panel is found, get a reference to the panel_bridge when it
>>    is added, so the following code always get exactly one reference that
>>    it needs to put
>>
>> Finally, use the next_bridge pointer in struct drm_bridge in order to
>> simplify putting the reference.
>>
>> Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
>
> I do not understand the change as a whole but the approach
> looks sane so:
> Acked-by: Linus Walleij <linusw@...nel.org>

Thanks!

However I'm not adding your A-by to v2. The change you suggested to patch 3
(break instead of warn) made the drm_bridge_put() call in this patch
unnecessary, so I dropped it for v2, making this patch slightly different.

I hope you'll Ack v2 too. :)

Luca

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