On Thu, 16 Jul 2009, Zhang Rui wrote: > > > Laptops often have more than one video bus device, and you _have_ to choose > > > the one that is _active_ (which might not be the first one you find). This > > > is done on laptops that can have either discrete or in-chipset graphics, for > > > example. I have seen it in several thinkpad models. > > > > The video subsystem already picks only graphics devices that actually > > exist in the PCI bus. The issue here is that there are two ACPI > > "subdevices" under one address reference to a PCI device (which exists), > > and both have backlight functionality. > > right. > For example, > here is a laptop with both an integrated graphics (\_SB.PCI0.GFX0) and > an external graphics (\_SB.PCI0.NVDI) > we can find which one is active, NVDI or GFX0, and ignore the inactive > one. Well, those will likely change at runtime if we do our job properly to support dual-GPU laptops that can change which one is active at runtime... but hotplug support should be able to deal with it, but I don't know if the ACPI video device does runtime hotplug/unplug and runtime bind/unbind properly. Does it? However, some laptops (like my T43) do have two video devices, one of which will never be enabled (because it is there for a separate mainboard which has a different GPU). This is correctly handled currently. > But the bug that I want to fix in this patch is that, > there are two ACPI video bus devices > \_SB.PCI0.GFX0.VID1 > ???\_SB.PCI0.GFX0.VID2 > both are active because PCI device GFX0 exists, and ACPI tries to bind > all these two devices to ACPI video driver. > it's meaningless to have two ACPI video bus device for one VGA > controller, right? Unless your ACPI tables control each CRTC of the device separately... most GPUs have at least two CRTCs nowadats, and that might mean two backlight controllers as well, btw. But this doesn't look like what happens on the platform with the bug by the descriptions in this thread, and I know of no device that would try to do something as crazy as what I described (if it is allowed at all by the ACPI spec, which I didn't check)... > and it messes up the backlight controller because notifications are sent > to both VID1 and VID2 when brightness hotkey is pressed. If you had *two* backlight controllers, that should just mean you are to step them up/down together, nothing else... However, if they handle the same brightness hardware, yes, it _will_ cause problems (double stepping, for example). -- "One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie." -- The Silicon Valley Tarot Henrique Holschuh -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
