On Thu, Oct 09, 2014 at 04:27:55PM +0800, Aaron Lu wrote: > On 10/01/2014 04:18 AM, Rafael J. Wysocki wrote: > > On Tuesday, September 30, 2014 02:10:17 PM Aaron Lu wrote: > >> The _DOD method lists which video output device is currently attached so > >> we should only care about them and ignore others. An user recently > >> reported that there are two acpi_video interfaces appeared on his system > >> and one of them doesn't work. From the acpidump, it is found that there > >> are more than one video output devices that have _BCM control method but > >> the _DOD lists only one of them. So this patch checks if the video output > >> device is in the _DOD list and will not create backlight device if it is > >> not in the list. Also, we consider the broken _DOD case(reflected by the > >> video->attached_count is 0) and do not change behaviour for those broken > >> _DOD systems. > >> > >> Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=84111 > >> Reported-and-tested-by: ntrrgc@xxxxxxxxx > >> Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx> > > > > This looks reasonable to me, but I'm a little afraid that it may break > > systems which forget to list valid interfaces in the _DOD. > > Indeed, this is possible. And indeed, there is a regression! My Dell Latituded E6410's backlight control no longer works after this commit, and I get messages like this instead: [ 57.214610] ACPI: Failed to switch the brightness If I revert this commit, my backlight controls work again. Also, I regain a cooling device (?) that was being ignored: [ 1.332682] acpi device:02: registered as cooling_device0 Do you need any additional info to handle the regression, or should we just revert the patch? Brian -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
