454d61a56d
Testing has shown that there are quite a few laptop models which rely on native backlight control and which do not support ACPI video bus backlight control, causing __acpi_video_get_backlight_type() to return vendor. Known Windows laptop models affected by this are: Acer Aspire 1640 HP Compaq nc6120 IBM ThinkPad X40 System76 Starling Star1 and the following MacBook models are affected too: Apple MacBook 2.1 Apple MacBook 4.1 Apple MacBook Pro 7.1 the list of affected Windows laptop models is likely just the top of the iceberg. So for now lets undo the change to not register native backlight class devices when __acpi_video_get_backlight_type() != native. Since as part of the backlight-detect refactor the detection code now relies on the GPU drivers calling acpi_video_backlight_use_native() to learn that native backlight support is available we cannot just remove the acpi_video_backlight_use_native() calls from the GPU drivers. Instead modify acpi_video_backlight_use_native() to always return true for now. This is meant as a temporary work-around, which will be removed again when the heuristics from __acpi_video_get_backlight_type() have been improved so that they will return native on affected models. Reported-by: Matthew Garrett <mjg59@srcf.ucam.org> Reported-by: John Warriner <taijitu@cox.net> Reported-by: Scott Ostrander <sos12_3@hotmail.com> Reported-by: Matthias Rampke <matthias.rampke@googlemail.com> Reported-by: Milan Hodoscek <hmilan@gmail.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
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
``make pdfdocs``. The formatted documentation can also be read online at:
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.