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520c2286c2
The underlying problem is the handling of the enabled bit in device
status (bit 1 of _STA return value) which is required by the ACPI
specification to be observed in addition to the present bit (bit 0
of _STA return value) [1], but Linux does not observe it.
Since Linux has not looked at that bit for a long time, it is generally
risky to start obseving it in all device enumeration cases, especially
at the system initialization time, but it can be observed when the
kernel receives a Bus Check or Device Check notification indicating a
change in device configuration. In those cases, seeing the enabled bit
clear may be regarded as an indication that the device at hand should
not be used any more.
For this reason, rework the handling of Device Check and Bus Check
notifications in the ACPI core device enumeration code in the
following way:
1. Rename acpi_bus_trim_one() to acpi_scan_check_and_detach() and make
it check device status if its second argument is not NULL, in which
case it will detach scan handlers or ACPI drivers from devices whose
_STA returns the enabled bit clear.
2. Make acpi_scan_device_check() and acpi_scan_bus_check() invoke
acpi_scan_check_and_detach() with a non-NULL second argument
unconditionally, so scan handlers and ACPI drivers are detached
from the target device and its ancestors if their _STA returns the
enabled bit clear.
Link: https://uefi.org/specs/ACPI/6.5/06_Device_Configuration.html#sta-device-status # [1]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
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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.