Hans de Goede 30b3075be4 platform/x86: nvidia-wmi-ec-backlight: Add force module parameter
commit 0d9bdd8a55 upstream.

On some Lenovo Legion models, the backlight might be driven by either
one of nvidia_wmi_ec_backlight or amdgpu_bl0 at different times.

When the Nvidia WMI EC backlight interface reports the backlight is
controlled by the EC, the current backlight handling only registers
nvidia_wmi_ec_backlight (and registers no other backlight interfaces).

This hides (never registers) the amdgpu_bl0 interface, where as prior
to 6.1.4 users would have both nvidia_wmi_ec_backlight and amdgpu_bl0
and could work around things in userspace.

Add a force module parameter which can be used with acpi_backlight=native
to restore the old behavior as a workound (for now) by passing:

"acpi_backlight=native nvidia-wmi-ec-backlight.force=1"

Fixes: 8d0ca287fd ("platform/x86: nvidia-wmi-ec-backlight: Use acpi_video_get_backlight_type()")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217026
Cc: stable@vger.kernel.org
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Daniel Dadap <ddadap@nvidia.com>
Link: https://lore.kernel.org/r/20230217144208.5721-1-hdegoede@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-02-25 11:25:43 +01:00
2023-02-25 11:25:42 +01:00
2022-09-28 09:02:20 +02:00
2022-09-28 09:02:20 +02:00
2023-02-22 12:59:56 +01:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
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    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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