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The value in "new" is constructed from "old" such that all bits defined as reserved by the ACPI spec[1] are left untouched. But if those bits do not happen to be all zero, "new < 3" will not evaluate to true. The firmware of the laptop(s) Medion MD63490 / Akoya P15648 comes with garbage inside the "FACS" ACPI table. The starting value is old=0x4944454d, therefore new=0x4944454e, which is >= 3. Mask off the reserved bits. [1] https://uefi.org/sites/default/files/resources/ACPI_6_2.pdf Link: https://bugzilla.kernel.org/show_bug.cgi?id=206553 Cc: All applicable <stable@vger.kernel.org> Signed-off-by: Jan Engelhardt <jengelh@inai.de> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.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.