linux-kernel - Re: [PATCH 3/5] drm/panel: get/put panel reference in drm_panel

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Message-ID: <20250326102307.5ee0cb83@booty>
Date: Wed, 26 Mar 2025 10:23:07 +0100
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Anusha Srivatsa <asrivats@...hat.com>
Cc: Neil Armstrong <neil.armstrong@...aro.org>, Jessica Zhang
 <quic_jesszhan@...cinc.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 3/5] drm/panel: get/put panel reference in
 drm_panel_add/remove()

On Tue, 25 Mar 2025 13:24:10 -0400
Anusha Srivatsa <asrivats@...hat.com> wrote:

> Take the panel reference and put it back as required
> using the helpers introduced in previous patch.
> drm_panel_add() and drm_panel_remove()
> add a panel to the global registry and removes a panel
> respectively, use get() and put() helpers to keep up
> with refcounting.
> 
> Signed-off-by: Anusha Srivatsa <asrivats@...hat.com>

This is OK but is should not be applied until all panel drivers are
converted to the new devm_drm_panel_alloc() API. Otherwise for
not-yet-converted panel drivers drm_panel_get/put() would operate on an
uninitialized kref. See [0].

# Do not apply until all panel drivers are converted!
Reviewed-by: Luca Ceresoli <luca.ceresoli@...tlin.com>

[0] https://lore.kernel.org/all/20250317155607.68cff522@booty/

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