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Message-ID: <746e5cc6-516f-8f69-9d4b-8fe237de8fd6@redhat.com>
Date:   Mon, 24 Oct 2022 13:53:05 +0200
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Subject: Re: [PATCH 00/22] Fallback to native backlight
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To:     Akihiko Odaki <akihiko.odaki@daynix.com>
Cc:     David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Jonathan Corbet <corbet@lwn.net>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Len Brown <lenb@kernel.org>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
        "Lee, Chun-Yi" <jlee@suse.com>, Mark Gross <markgross@kernel.org>,
        Corentin Chary <corentin.chary@gmail.com>,
        Cezary Jackiewicz <cezary.jackiewicz@gmail.com>,
        Matthew Garrett <mjg59@srcf.ucam.org>,
        =?UTF-8?Q?Pali_Roh=c3=a1r?= <pali@kernel.org>,
        Jonathan Woithe <jwoithe@just42.net>,
        Ike Panhc <ike.pan@canonical.com>,
        Daniel Dadap <ddadap@nvidia.com>,
        Kenneth Chan <kenneth.t.chan@gmail.com>,
        Mattia Dongili <malattia@linux.it>,
        Henrique de Moraes Holschuh <hmh@hmh.eng.br>,
        Azael Avalos <coproscefalo@gmail.com>,
        Lee Jones <lee@kernel.org>,
        Daniel Thompson <daniel.thompson@linaro.org>,
        Jingoo Han <jingoohan1@gmail.com>,
        Helge Deller <deller@gmx.de>,
        Robert Moore <robert.moore@intel.com>,
        dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
        intel-gfx@lists.freedesktop.org,
        platform-driver-x86@vger.kernel.org,
        acpi4asus-user@lists.sourceforge.net,
        ibm-acpi-devel@lists.sourceforge.net, linux-fbdev@vger.kernel.org,
        devel@acpica.org
References: <20221024113513.5205-1-akihiko.odaki@daynix.com>
From:   Hans de Goede <hdegoede@redhat.com>
In-Reply-To: <20221024113513.5205-1-akihiko.odaki@daynix.com>
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Precedence: bulk

Hi Akihiko,

On 10/24/22 13:34, Akihiko Odaki wrote:
> Commit 2600bfa3df99 ("ACPI: video: Add acpi_video_backlight_use_native()
> helper") and following commits made native backlight unavailable if
> CONFIG_ACPI_VIDEO is set and the backlight feature of ACPI video is
> unavailable, which broke the backlight functionality on Lenovo ThinkPad
> C13 Yoga Chromebook. Allow to fall back to native backlight in such
> cases.

I appreciate your work on this, but what this in essence does is
it allows 2 backlight drivers (vendor + native) to get registered
for the same panel again. While the whole goal of the backlight refactor
series landing in 6.1 was to make it so that there always is only
*1* backlight device registered instead of (possibly) registering
multiple and letting userspace figure it out. It is also important
to only always have 1 backlight device per panel for further
upcoming changes.

So nack for this solution, sorry.

I am aware that this breaks backlight control on some Chromebooks,
this was already reported and I wrote a long reply explaining why
things are done the way they are done now and also suggesting
2 possible (much simpler) fixes, see:
https://lore.kernel.org/linux-acpi/42a5f2c9-a1dc-8fc0-7334-fe6c390ecfbb@redhat.com/

Unfortunately the reported has not followed-up on this and
I don't have the hardware to test this myself.

Can you please try implementing 1 of the fixes suggested there
and then submit that upstream ?

Regards,

Hans


> 
> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> 
> Akihiko Odaki (22):
>   drm/i915/opregion: Improve backlight request condition
>   ACPI: video: Introduce acpi_video_get_backlight_types()
>   LoongArch: Use acpi_video_get_backlight_types()
>   platform/x86: acer-wmi: Use acpi_video_get_backlight_types()
>   platform/x86: asus-laptop: Use acpi_video_get_backlight_types()
>   platform/x86: asus-wmi: Use acpi_video_get_backlight_types()
>   platform/x86: compal-laptop: Use acpi_video_get_backlight_types()
>   platform/x86: eeepc-laptop: Use acpi_video_get_backlight_types()
>   platform/x86: fujitsu-laptop: Use acpi_video_get_backlight_types()
>   platform/x86: ideapad-laptop: Use acpi_video_get_backlight_types()
>   platform/x86: msi-laptop: Use acpi_video_get_backlight_types()
>   platform/x86: msi-wmi: Use acpi_video_get_backlight_types()
>   platform/x86: nvidia-wmi-ec-backlight: Use
>     acpi_video_get_backlight_types()
>   platform/x86: panasonic-laptop: Use acpi_video_get_backlight_types()
>   platform/x86: samsung-laptop: Use acpi_video_get_backlight_types()
>   platform/x86: sony-laptop: Use acpi_video_get_backlight_types()
>   platform/x86: thinkpad_acpi: Use acpi_video_get_backlight_types()
>   platform/x86: toshiba_acpi: Use acpi_video_get_backlight_types()
>   platform/x86: dell-laptop: Use acpi_video_get_backlight_types()
>   platform/x86: intel_oaktrail: Use acpi_video_get_backlight_types()
>   ACPI: video: Remove acpi_video_get_backlight_type()
>   ACPI: video: Fallback to native backlight
> 
>  Documentation/gpu/todo.rst                    |  8 +--
>  drivers/acpi/acpi_video.c                     |  2 +-
>  drivers/acpi/video_detect.c                   | 54 ++++++++++---------
>  drivers/gpu/drm/i915/display/intel_opregion.c |  3 +-
>  drivers/platform/loongarch/loongson-laptop.c  |  4 +-
>  drivers/platform/x86/acer-wmi.c               |  2 +-
>  drivers/platform/x86/asus-laptop.c            |  2 +-
>  drivers/platform/x86/asus-wmi.c               |  4 +-
>  drivers/platform/x86/compal-laptop.c          |  2 +-
>  drivers/platform/x86/dell/dell-laptop.c       |  2 +-
>  drivers/platform/x86/eeepc-laptop.c           |  2 +-
>  drivers/platform/x86/fujitsu-laptop.c         |  4 +-
>  drivers/platform/x86/ideapad-laptop.c         |  2 +-
>  drivers/platform/x86/intel/oaktrail.c         |  2 +-
>  drivers/platform/x86/msi-laptop.c             |  2 +-
>  drivers/platform/x86/msi-wmi.c                |  2 +-
>  .../platform/x86/nvidia-wmi-ec-backlight.c    |  2 +-
>  drivers/platform/x86/panasonic-laptop.c       |  2 +-
>  drivers/platform/x86/samsung-laptop.c         |  2 +-
>  drivers/platform/x86/sony-laptop.c            |  2 +-
>  drivers/platform/x86/thinkpad_acpi.c          |  4 +-
>  drivers/platform/x86/toshiba_acpi.c           |  2 +-
>  drivers/video/backlight/backlight.c           | 18 +++++++
>  include/acpi/video.h                          | 21 ++++----
>  include/linux/backlight.h                     |  1 +
>  25 files changed, 85 insertions(+), 66 deletions(-)
>