On 07/31/2013 08:01 AM, Rafael J. Wysocki wrote: > On Thursday, July 18, 2013 02:16:09 AM Rafael J. Wysocki wrote: >> On Sunday, June 09, 2013 07:01:36 PM Matthew Garrett wrote: >>> Windows 8 introduced new policy for backlight control by pushing it out to >>> graphics drivers. This appears to have coincided with a range of vendors >>> adding Windows 8 checks to their backlight control code which trigger either >>> awkward behaviour (Lenovo) or complete brokenness (some Dells). The simplest >>> thing to do would be to just disable ACPI backlight control entirely if the >>> firmware indicates Windows 8 support, but it's entirely possible that >>> individual graphics drivers might still make use of the ACPI functionality in >>> preference to native control. >>> >>> The first two patches in this series are picked from other patchesets aimed at >>> solving similar problems. The last simply unregisters ACPI backlight control >>> on Windows 8 systems when using an Intel GPU. Similar code could be added to >>> other drivers, but I'm reluctant to do so without further investigation as >>> to the behaviour of the vendor drivers under Windows. >> >> Well, after some more time spent on that, we now have a series of 3 patches >> (different from the $subject one) that we think may be used to address this >> issue. As far as I can say, it has been tested by multiple people whose >> systems have those problems and they generally saw improvement. >> >> It is not my ideal approach, but it seems to be the least intrusive and/or >> with the least amount of possible side effects that we can do right now >> as a general measure (alternatively, we could create a possibly long >> blacklist table of affected systems with different workarounds for them, >> but let's just say that is not overwhelmingly attractive). >> >> [1/3] Make ACPICA export things that we need for checking OSI(Win8). >> >> [2/3] Make acpi_video_device_find_cap() call acpi_video_init_brightness() even >> if it is not going to register the backlight interface (needed for >> Thinkpads). >> >> [3/3] Avoid using ACPI backlight if i915 is in use and the firmware believes >> we are Windows 8. >> >> Many thanks to everyone involved! > > So this didn't work, as we had to revert [3/3], but I think we should try to > make some progress with this nevertheless. A way forward I'm seeing now could > be to > (1) Split the ACPI video driver so that it is possible to register the > backlight control separately from the event interface. > (2) Add a command line option to i915 to make it use the native backlight > control (without registering the ACPI one) if set. Make unset the > default initially. > (3) Fix i915 backlight control issues for all systems known to have them > (that may take a while) and flip the defailt for that option to set when we > think we're ready. > (4) If there still are problem reports, flip the default back to unset and > repeat (3). > > If this converges, everyone will be using the native backlight control by > default and the original problem will go away automatically. > > Thoughts? Sounds good to me. -Aaron _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
