• Hans de Goede's avatar
    ACPI / video: Only default only_lcd to true on Win8-ready _desktops_ · 53fa1f6e
    Hans de Goede authored
    Commit 5928c281 (ACPI / video: Default lcd_only to true on Win8-ready
    and newer machines) made only_lcd default to true on all machines where
    acpi_osi_is_win8() returns true, including laptops.
    
    The purpose of this is to avoid the bogus / non-working acpi backlight
    interface which many newer BIOS-es define on desktop machines.
    
    But this is causing a regression on some laptops, specifically on the
    Dell XPS 13 2013 model, which does not have the LCD flag set for its
    fully functional ACPI backlight interface.
    
    Rather then DMI quirking our way out of this, this commits changes the
    logic for setting only_lcd to true, to only do this on machines with
    a desktop (or server) dmi chassis-type.
    
    Note that we cannot simply only check the chassis-type and not register
    the backlight interface based on that as there are some laptops and
    tablets which have their chassis-type set to "3" aka desktop. Hopefully
    the combination of checking the LCD flag, but only on devices with
    a desktop(ish) chassis-type will avoid the needs for DMI quirks for this,
    or at least limit the amount of DMI quirks which we need to a minimum.
    
    Fixes: 5928c281 (ACPI / video: Default lcd_only to true on Win8-ready and newer machines)
    Reported-and-tested-by: default avatarJames Hogan <jhogan@kernel.org>
    Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
    Cc: 4.15+ <stable@vger.kernel.org> # 4.15+
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    53fa1f6e
acpi_video.c 57.9 KB