On Thursday, July 25, 2013 03:34:10 PM Jani Nikula wrote: > On Thu, 25 Jul 2013, "Rafael J. Wysocki" <rjw@xxxxxxx> wrote: > > On Thursday, July 25, 2013 11:09:27 AM Jani Nikula wrote: > >> On Thu, 25 Jul 2013, "Rafael J. Wysocki" <rjw@xxxxxxx> wrote: > >> > 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. :-) > > I didn't claim it didn't work, just that *I* didn't see how it could. ;) > > >> 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(). > > Right. I totally missed the call within the ternary operator. Thanks for > the explanation, and apologies for the noise. > > >> 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. > > I observe that for the regular non-quirk acpi_video_register() call, > acpi_video_backlight_quirks() won't be called during register, but it > will get called later. This might have subtle effects later on, don't > you think? Yes, it might, but after dropping ACPI_VIDEO_SKIP_BACKLIGHT it should be OK. > As to the original problem, and your patch in this thread, what do you > think about having another value in acpi_backlight kernel parameter for > it? Having an i915 module parameter to tell acpi to use or not use > quirks seems odd, since the i915 is not really taking over > anything. It's just passing the info on to acpi. I agree, I'm going to send a full revert in a while and we'll think what to do about all that later. 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
