On Mon, Sep 22, 2014 at 06:10:50PM -0400, Alex Deucher wrote: > > > > With dual VGA controllers, we can change VGA routing in the chipset so > > that we can address one device or the other using the VGA address space. > > This lets things like Xorg switch between cards to initialize a card via > > the VGA BIOS or execute runtime VGA BIOS calls. If one of those devices > > reports itself as a 3D controller, then we have no reason to believe > > that the device actually responds to VGA accesses or that the PCI ROM > > payload includes a VGA BIOS. > > > > Maybe that's how the arbiter device registration should work, if the > > class code is VGA add it, if it's 3D controller, switch VGA routing and > > see if it responds to VGA. There are still a couple problems that I've > > been beating my head against though. First, i915 lies when it opts-out > > of VGA arbitration, so you might think you've found a VGA device > > elsewhere, but you're actually still talking to IGD. Second is the Xorg > > DRI problem where it's going to disable DRI support if suddenly a second > > arbitration participant appears. This is what happened when I tried to > > fix the i915 problem and suddenly anybody with IGD + plugin graphics > > lost DRI and the fix was reverted. The whole thing is pretty broken. > > > > In this case, if your laptop actually supports disabling and hiding the > > IGD device, I'd expect the Nvidia device to switch to reporting itself > > as VGA. It seems like often the Optimus graphics aren't even directly > > connected to an output device, which makes me curious that you can > > actually pick one or the other. Thanks, > > AFAIK, on most recent (like in the last 2-3 years) hybrid laptops > don't really have the option to boot to the dGPU or even disable the > integrated graphics (I'm not sure that was ever possibly, even on the > old muxed ones). Depending on the OEM, the dGPU may be wired to one > or more of the external ports, but I don't think those are usable > until after the drivers have loaded. Newer radeon PowerXpress laptops > mark the dGPU as PCI_CLASS_DISPLAY_OTHER and I don't think there is > any expectation that they should be messing with vga. > I had Lenovo T430 hybrid graphics laptop earlier, which is in "last 2-3 years", and it allowed me to choose "IGD only", "Optimus", or "Nvidia only" in BIOS.. -- Pasi > Alex > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
