On 11/28/2014 05:59 PM, Brian Norris wrote: > 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? Please attach acpidump, dmesg with video.dyndbg="module video +pft" in kernel cmdline, list the /sys/class/backlight with and without this commit, thanks. -Aaron > > 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
