On Wed, Sep 11, 2013 at 11:45:19AM +0300, Jani Nikula wrote: > On Wed, 11 Sep 2013, Aaron Lu <aaron.lu@xxxxxxxxx> wrote: > > It is possible the i915 driver decides not to register a backlight > > interface for the graphics card for some reason(memory allocation failed > > or it knows the native control does not work on this card or whatever), > > so I would prefer let i915 tell ACPI video that it has registered a > > native backlight control interface as Jani has said. > > > > Then together with the video.use_native_backlight, we can register or > > not register ACPI video backlight interface accordingly. Or rather, we > > can simply not register ACPI video backlight interface for Win8 systems > > as long as i915 indicates that it has native backlight control(if the > > native control is broken, i915 should fix it or blacklist it so that > > i915 will not indicate it has native backlight control and ACPI video > > will continue to register its own). > > > > How does this sound? > > Sounds good to me. > > Before plunging forward, have you observed any difference between the > boot modes? We have reports [1] that the backlight behaviour is Not yet from ACPI's point of view. > different with UEFI vs. UEFI+CSM or legacy boot. So I'm wondering if the > acpi_gbl_osi_data >= ACPI_OSI_WIN_8 check in patch 2/2 is the whole > story. This check in patch 2/2 is a policy: for Win8 system, we think the native backlight control has a better chance of working than the ACPI video's, so I think the check is enough in ACPI video. > > Further, if we tell the BIOS we're Windows 8 to use the tested BIOS code > paths, what guarantees do we have of UEFI+CSM or legacy boots working? I suppose the 'tested BIOS code paths' means the pure UEFI boot mode? I don't know what guatantees do we have since I don't know what happened underneath after the backlight register is set in i915 driver, you or other i915 driver people should know more than I do :-) BTW, after the backlight register is set in i915, is it that some find of firmware code will run in response to the setting of the register(e.g. the BLC_PWM_CTL/BLC_PWM_CPU_CTL/PCI_LBPC reg)? Thanks, Aaron _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
