linux-kernel - Re: [RFC PATCH 04/10] drm/panel_helper: Introduce drm_panel

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Date:   Mon, 7 Aug 2023 08:41:05 +0200
From:   Maxime Ripard <mripard@...nel.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     dri-devel@...ts.freedesktop.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 04/10] drm/panel_helper: Introduce drm_panel_helper

Hi Doug,

Thanks for working on this :)

On Fri, Aug 04, 2023 at 02:06:07PM -0700, Douglas Anderson wrote:
> The goal of this file is to contain helper functions for panel drivers
> to use. To start off with, let's add drm_panel_helper_shutdown() for
> use by panels that want to make sure they're powered off at
> shutdown/remove time if they happen to be powered on.
> 
> The main goal of introducting this function is so that panel drivers
> don't need to track the enabled/prepared state themselves.
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

It shouldn't be necessary at all: drivers should call
drm_atomic_helper_shutdown at removal time which will disable the
connector (which in turn should unprepare/disable its panel).

If either the driver is missing drm_atomic_helper_shutdown, or if the
connector doesn't properly disable the panel, then I would consider that
a bug.

Maxime

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