On Thursday, July 25, 2013 11:09:27 AM Jani Nikula wrote: > On Thu, 25 Jul 2013, "Rafael J. Wysocki" <rjw@xxxxxxx> wrote: > > On Wednesday, July 24, 2013 02:05:15 PM Linus Torvalds wrote: > >> On Wed, Jul 24, 2013 at 2:02 PM, Daniel Vetter <daniel.vetter@xxxxxxxx> wrote: > >> > > >> > I think a i915 module option should be doable, otoh people seem to have a > >> > viable workaround by setting a different acpi os version already. > >> > >> At least the original claim was that if you set a non-windows8 acpi os > >> version, you hit other bugs.. > >> > >> But yeah, if we just do a plain revert, that may be the only option > >> for the people for whom the current (to-be-reverted) patches made > >> things work. > > > > Well, I wonder what about the appended (untested) patch? > > Rafael, before going there, I've been trying to wrap my (poor, rusty > after vacation) head around > > commit 8c5bd7adb2ce47e6aa39d17b2375f69b0c0aa255 > Author: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > Date: Thu Jul 18 02:08:06 2013 +0200 > > ACPI / video / i915: No ACPI backlight if firmware expects Windows 8 > > and I can't see how it could work. Well, if it didn't work, people wouldn't see either improvement or breakage from it, but they do see that, so it evidently works. :-) > First, the ACPI_VIDEO_SKIP_BACKLIGHT flag seems to be checked before > it's actually set anywhere. Are you sure about that? acpi_video_bus_add() is the .add() callback routine for acpi_video_bus which in fact is an ACPI driver (the naming sucks, but I didn't invent it). This means that acpi_video_bus_add() can only be called *after* acpi_video_bus has been registered with the ACPI subsystem (and the driver core). That is done by acpi_bus_register_driver() and, guess what?, this happens in __acpi_video_register(). So clearly, acpi_video_bus_add() *cannot* run before __acpi_video_register(). > Buried deep in the calls from > acpi_video_bus_add(), acpi_video_verify_backlight_support() is used > before acpi_video_backlight_quirks() gets called. (Perhaps if i915 is > reloaded, this goes right as the flags are already set.) Please see above. > Second, with i915 that has opregion support, __acpi_video_register() > should only ever get called once. Which means the acpi_walk_namespace() > with video_unregister_backlight() should never get called in register. > > Please enlighten me. Actually, that's correct, so we don't need the whole video_unregister_backlight() thing, calling acpi_video_backlight_quirks() would be sufficient. Ah, one more reason to do a full revert. I'm thinking, though, that I'll leave acpi_video_backlight_quirks() as is so that it can be used by acpi_video_bus_(start)|(stop)_devices(), because that doesn't seem to cause problems to happen. Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
