linux-kernel - Re: [PATCH] drm/tidss: encoder: convert to devm_drm_bridge

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Message-Id: <DBE5Z1SRJ086.NA0KUAWX1MS3@kernel.org>
Date: Thu, 17 Jul 2025 09:49:44 +0200
From: "Michael Walle" <mwalle@...nel.org>
To: "Luca Ceresoli" <luca.ceresoli@...tlin.com>
Cc: "Jyri Sarha" <jyri.sarha@....fi>, "Tomi Valkeinen"
 <tomi.valkeinen@...asonboard.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>,
 <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/tidss: encoder: convert to devm_drm_bridge_alloc()

Hi,

thanks for taking a look!

> However allocating an encoder using a bridge alloc function (while we
> used to call an encoder allocation function) looks counter-intuitive.
>
> We had discussed on IRC a different idea, adding a wrapper structure
> around the bridge. Quoting your proposal:
>
>   struct tidss_encoder_bridge {
>     struct drm_bridge bridge;
>     struct tidss_encoder *encoder
>   }
>
> and then in the bridge funcs go from drm_bridge to tidss_encoder_brigde
> and use the pointer to get the original private struct.

I was doing that until I've realized that meson/meson_encoder_* is
doing it the way this patch does it.

> That would be cleaner and more intuitive, but use a bit more memory and
> have an additional pointer deref, thus I think we can live with the
> patch you just sent, at least for now.

I'm fine with changing it to the wrapper struct. It's your/the
maintainers call :)

-michael

> In the long term it may be that more and more components of the DRM
> subsystem become dynamically allocated like bridges and panels [0] have
> recently become. So at some point it may make sense to add the bridge
> wrapper struct and then go back to drmm_simple_encoder_alloc() for
> allocation.
>
> [0] https://lore.kernel.org/all/20250331-b4-panel-refcounting-v4-1-dad50c60c6c9@redhat.com/
>
> Luca

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