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Date: Wed, 11 Sep 2013 11:45:19 +0300 From: Jani Nikula <jani.nikula@...ux.intel.com> To: Aaron Lu <aaron.lu@...el.com>, "Rafael J. Wysocki" <rjw@...k.pl> Cc: Daniel Vetter <daniel@...ll.ch>, Aaron Lu <aaron.lu@...el.com>, ACPI Devel Mailing List <linux-acpi@...r.kernel.org>, Matthew Garrett <matthew.garrett@...ula.com>, Daniel Vetter <daniel.vetter@...ll.ch>, "intel-gfx\@lists.freedesktop.org" <intel-gfx@...ts.freedesktop.org>, Yves-Alexis Perez <corsac@...ian.org>, "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>, "dri-devel\@lists.freedesktop.org" <dri-devel@...ts.freedesktop.org>, Seth Forshee <seth.forshee@...onical.com>, "Lee\, Chun-Yi" <joeyli.kernel@...il.com>, Igor Gnatenko <i.gnatenko.brain@...il.com>, Henrique de Moraes Holschuh <hmh@....eng.br>, Lee Chun-Yi <jlee@...ell.com>, Len Brown <lenb@...nel.org> Subject: Re: [PATCH 2/2] ACPI / video / i915: Remove ACPI backlight if firmware expects Windows 8 On Wed, 11 Sep 2013, Aaron Lu <aaron.lu@...el.com> 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 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. 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? BR, Jani. [1] https://bugzilla.kernel.org/show_bug.cgi?id=47941#c96 -- Jani Nikula, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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