Comment 33 for bug 121833

Thanks Dana. I'm including the corresponding upstream git commit id's for the kernel team to reference. Thanks.

commit 38531e6fe51ad5c7dfe72e0e066b5f54bc1921cd
Author: Matthew Garrett <email address hidden>
Date: Wed Dec 26 02:03:26 2007 +0000

    ACPI: video: Rationalise ACPI backlight implementation

    The sysfs backlight class provides no mechanism for querying the
    acceptable brightness for a backlight. The ACPI spec states that values
    are only valid if they are reported as available by the firmware. Since
    we can't provide that information to userspace, instead collapse the
    range to the number of actual values that can be set.

    http://bugzilla.kernel.org/show_bug.cgi?id=9277

    Signed-off-by: Matthew Garrett <email address hidden>
    Acked-by: Zhang Rui <email address hidden>
    Signed-off-by: Len Brown <email address hidden>

commit 3fa2cdcc45a0176de15cac9dbf4ed2834ebf8932
Author: Matthew Garrett <email address hidden>
Date: Thu Feb 7 01:44:06 2008 +0000

    ACPI: video: Ignore ACPI video devices that aren't present in hardware

    Vendors often ship machines with a choice of integrated or discrete
    graphics, and use the same DSDT for both. As a result, the ACPI video
    module will locate devices that may not exist on this specific platform.

    Attempt to determine whether the device exists or not, and abort the
    device creation if it do not exist.

    Signed-off-by: Matthew Garrett <email address hidden>
    Signed-off-by: Len Brown <email address hidden>