linux-kernel - Re: [PATCH v2 2/2] HID: Make elan touch controllers power on after panel is enabled

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Message-ID: <CAD=FV=XmMwocA_oZVi2OS2Z4+5LBT4BXZE2C1mx1U-Tcs+5SOg@mail.gmail.com>
Date: Thu, 14 Aug 2025 17:19:25 -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>, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, linux-input@...r.kernel.org, 
	Chen-Yu Tsai <wenst@...omium.org>
Subject: Re: [PATCH v2 2/2] HID: Make elan touch controllers power on after
 panel is enabled

Hi,

On Wed, Aug 13, 2025 at 5:51 AM Pin-yen Lin <treapking@...omium.org> wrote:
>
> Introduce a new HID quirk to indicate that this device has to be enabled
> after the panel's backlight is enabled, and update the driver data for
> the elan devices to enable this quirk. This cannot be a I2C HID quirk
> because the kernel needs to acknowledge this before powering up the
> device and read the VID/PID. When this quirk is enabled, register
> .panel_enabled()/.panel_disabling() instead for the panel follower.
>
> Also rename the *panel_prepare* functions into *panel_follower* because
> they could be called in other situations now.
>
> Signed-off-by: Pin-yen Lin <treapking@...omium.org>
>
> ---
>
> Changes in v2:
> - Rename *panel_prepare* functions to *panel_follower*
> - Replace after_panel_enabled flag with enabled/disabling callbacks
>
>  drivers/hid/i2c-hid/i2c-hid-core.c    | 46 ++++++++++++++++-----------
>  drivers/hid/i2c-hid/i2c-hid-of-elan.c | 11 ++++++-
>  include/linux/hid.h                   |  2 ++
>  3 files changed, 40 insertions(+), 19 deletions(-)

This seems reasonable to me.

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

Given that this affects devices that we already had support for
(you're changing the behavior of two touchscreens), should it have a
Fixes tag?

We'll also need to figure out a process for landing the two patches. I
can easily land the first one in drm-misc-next, but then it'll be a
while before the i2c-hid one can land. Is it OK to wait?


-Doug