The Linux ACPI core locates the ACPI video devices for us and marks them
with ACPI_VIDEO_HID. Use that information to locate the video device
instead of a half-baked hunt for _BCL.
This uncouples the detection of the number of backlight brightness
levels on ThinkPads from the ACPI paths in vid_handle.
With this change, the driver should be able to always detect whether the
ThinkPad uses a 8-level or 16-level brightness scale even on newer
models for which the vid_handle paths have not been updated yet.
It will skip deactivated devices in the ACPI device tree, which is a
change in behaviour.
Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Matthew Garrett <mjg@redhat.com>
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