linux-kernel - Re: [PATCH v3] drm: of: Properly try all possible cases for bridge/panel detection

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Date:   Tue, 19 Apr 2022 11:56:50 +0200
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     airlied@...ux.ie, daniel@...ll.ch, dri-devel@...ts.freedesktop.org,
        jagan@...rulasolutions.com, linus.walleij@...aro.org,
        linux-kernel@...r.kernel.org, maarten.lankhorst@...ux.intel.com,
        mripard@...nel.org, thomas.petazzoni@...tlin.com,
        tzimmermann@...e.de
Subject: Re: [PATCH v3] drm: of: Properly try all possible cases for
 bridge/panel detection

Hi Paul,

On Sat 16 Apr 22, 23:21, Paul Cercueil wrote:
> Hi Paul,
> 
> This patch breaks the ingenic-drm driver.
> 
> It calls drm_of_find_panel_or_bridge(np, 0, i, ...) starting for i=0, until
> -ENODEV is returned, which does not happen anymore.
> 
> The idea is to probe all the connected panels/bridges, should it be done
> differently now?

I've sent out a different patch which restores -ENODEV at:
https://patchwork.freedesktop.org/patch/481135/

Feel free to try it and reply with tested-by/reviewed-by there.
I've also made a proposal in the thread to skip the "child node" mechanism
as soon as an of graph is present, which would allow covering more legit
cases with -ENODEV (the patch linked above doesn't cover all cases that
need -ENODEV).

Ideally we'd like to remove the child node mechanism entirely, but it may
already be part of a device-tree binding spec.

Cheers,

Paul

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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