linux-kernel - Re: [PATCH v3 1/2] drm/panel: Allow powering on panel follower after panel is enabled

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Message-ID: <CAD=FV=XZK3HO8iC3VyMH+fP_XG2ogSNvUWuUcPFUxn1jU6-JZA@mail.gmail.com>
Date: Mon, 18 Aug 2025 13:11:18 -0700
From: Doug Anderson <dianders@...omium.org>
To: Pin-yen Lin <treapking@...omium.org>
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>, 
	Jiri Kosina <jikos@...nel.org>, Benjamin Tissoires <bentiss@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-input@...r.kernel.org, Chen-Yu Tsai <wenst@...omium.org>, 
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v3 1/2] drm/panel: Allow powering on panel follower after
 panel is enabled

Hi,

On Mon, Aug 18, 2025 at 4:50 AM Pin-yen Lin <treapking@...omium.org> wrote:
>
> Some touch controllers have to be powered on after the panel's backlight
> is enabled. To support these controllers, introduce .panel_enabled() and
> .panel_disabling() to panel_follower_funcs and use them to power on the
> device after the panel and its backlight are enabled.
>
> Signed-off-by: Pin-yen Lin <treapking@...omium.org>
>
> ---
>
> Changes in v3:
> - Update kernel-docs of drm_panel_add_follower() and drm_panel_remove_follower()
> - Fix the order of calling .panel_disabling() and .panel_unpreparing()
> - Add a blank line before the goto label
>
> Changes in v2:
> - Replace after_panel_enabled flag with enabled/disabling callbacks
>
>  drivers/gpu/drm/drm_panel.c | 73 +++++++++++++++++++++++++++++++------
>  include/drm/drm_panel.h     | 14 +++++++
>  2 files changed, 76 insertions(+), 11 deletions(-)

Looks good to me now.

Reviewed-by: Douglas Anderson <dianders@...omium.org>

If there are no objections, I'll plan to apply patch #1 next week to
give people a little time to speak up. As per discussion in v2 [1],
unless we hear back an "Ack" from HID maintainers then patch #2 will
just need to wait a while before it can land in the HID tree.

Question for Jessica / Neil: what do you think about landing
${SUBJECT} patch in drm-misc-fixes instead of drm-misc-next? This is a
dependency for the next patch which is marked as a "Fix". It'll mean
that the patch can make it into mainline faster so the HID patch could
land faster. The patch is also pretty low risk...

[1] https://lore.kernel.org/r/CAD=FV=UV8_XGmxC=7Z18PEnj6wKz+yZQuV_4h+LJh_MNCqszvg@mail.gmail.com/


-Doug