linux-kernel - Re: [PATCH v4 20/25] drm/tilcdc: Use devm_drm_of_get

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Message-ID: <20260122-camouflaged-cat-of-sorcery-7af8cf@houat>
Date: Thu, 22 Jan 2026 15:03:21 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>
Cc: "Kory Maincent (TI.com)" <kory.maincent@...tlin.com>, 
	Jyri Sarha <jyri.sarha@....fi>, Tomi Valkeinen <tomi.valkeinen@...asonboard.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Russell King <linux@...linux.org.uk>, Bartosz Golaszewski <brgl@...ev.pl>, 
	Tony Lindgren <tony@...mide.com>, Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Markus Schneider-Pargmann <msp@...libre.com>, 
	Bajjuri Praneeth <praneeth@...com>, Louis Chauvet <louis.chauvet@...tlin.com>, 
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>, Miguel Gazquez <miguel.gazquez@...tlin.com>, 
	Herve Codina <herve.codina@...tlin.com>, dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-omap@...r.kernel.org
Subject: Re: [PATCH v4 20/25] drm/tilcdc: Use devm_drm_of_get_bridge() helper

Hi,

On Mon, Jan 19, 2026 at 10:18:12PM +0100, Luca Ceresoli wrote:
> Maxime, I'd appreciate your opinion about the topic below.
> 
> On Fri Jan 16, 2026 at 6:02 PM CET, Kory Maincent (TI.com) wrote:
> > Replace drm_of_find_panel_or_bridge() with the newer
> > devm_drm_of_get_bridge() helper which simplifies the code by:
> > - Automatically handling both panel and bridge cases internally
> > - Managing the panel-to-bridge conversion when needed
> > - Using devres for resource management, eliminating manual cleanup
> >
> > This removes the need for explicit panel-to-bridge conversion via
> > devm_drm_panel_bridge_add_typed() and the associated error handling path.
> >
> > Signed-off-by: Kory Maincent (TI.com) <kory.maincent@...tlin.com>
> > ---
> >
> > Change in v4:
> > - New patch
> > ---
> >  drivers/gpu/drm/tilcdc/tilcdc_encoder.c | 18 ++++--------------
> >  1 file changed, 4 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/tilcdc/tilcdc_encoder.c b/drivers/gpu/drm/tilcdc/tilcdc_encoder.c
> > index a34a10337f6a8..546fe7e6ee815 100644
> > --- a/drivers/gpu/drm/tilcdc/tilcdc_encoder.c
> > +++ b/drivers/gpu/drm/tilcdc/tilcdc_encoder.c
> > @@ -55,15 +55,12 @@ int tilcdc_encoder_create(struct drm_device *ddev)
> >  	struct tilcdc_drm_private *priv = ddev_to_tilcdc_priv(ddev);
> >  	struct tilcdc_encoder *encoder;
> >  	struct drm_bridge *bridge;
> > -	struct drm_panel *panel;
> > -	int ret;
> >
> > -	ret = drm_of_find_panel_or_bridge(ddev->dev->of_node, 0, 0,
> > -					  &panel, &bridge);
> > -	if (ret == -ENODEV)
> > +	bridge = devm_drm_of_get_bridge(ddev->dev, ddev->dev->of_node, 0, 0);
> > +	if (PTR_ERR(bridge) == -ENODEV)
> 
> This patch is technically OK in the sense that the code before and after
> would be equivalent. However if it were me I would not do this change. The
> reason is that both drm_of_find_panel_or_bridge() and *_of_get_bridge() are
> problematic when introducing drm_bridge hotplug, which is the long-term
> goal I am working for, but *_of_get_bridge() is more problematic than
> drm_of_find_panel_or_bridge().
> 
> These functions are still there and not deprecated because there is
> currently no better replacement (and drm_bridge hotplug is not yet
> supported because of this and other things still to be done). To have a
> replacement, the panel_bridge lifetime needs to be reworked first and
> that's not going to happen overnight. So, all in all, if this patch is not
> crucial to your series I'd consider dropping it. But if it is important I'm
> fine with applying it, it won't make a huge difference.

Eh. I'm fine either way. I understand what you're saying, but this patch
doesn't introduce any *new* problem while it cleans up the driver, so I
guess we could merge it still. And further clean it up with what you
were suggesting later on.

Maxime

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