On Mon, Apr 16, 2018 at 04:25:12PM +0200, Pali Rohár wrote: > On Sunday 15 April 2018 21:05:23 Lukas Wunner wrote: > > On Sun, Apr 15, 2018 at 07:17:46PM +0200, Pali Rohár wrote: > > > On Saturday 14 April 2018 13:17:11 Lukas Wunner wrote: > > > > On Sat, Apr 14, 2018 at 12:49:50PM +0200, Pali Rohár wrote: > > > > > On Saturday 14 April 2018 12:45:12 Lukas Wunner wrote: > > > > > > On Thu, Apr 12, 2018 at 10:15:41PM +0800, Kai-Heng Feng wrote: > > > > > > > Do you have any suggestion to check if it connects to the system via > > > > > > > Thunderbolt? > > > > > > > > > > > > Just use pci_is_thunderbolt_attached(), introduced by 8531e283bee6, > > > > > > like this: > > > > > > > > > > > > if (check_dell_switchable_gfx(pci) && !pci_is_thunderbolt_attached(pci)) > > > > > > > > > > And what about PCI-e device attached to ExpressCard slot? > > > > > > > > I don't know of a bullet-proof way to recognize those. > > > > > > Hm... maybe another idea: Is it possible to detect which audio pci > > > device belongs to graphics card via vga_switcheroo? Currently, looking > > > at output it is same PCI device as graphic card, just different PCI > > > function. > > > > No, the DRM drivers don't filter ExpressCard-attached GPUs when > > registering with vga_switcheroo. > > > They do filter Thunderbolt-attached GPUs. > > So check via vga_switcheroo should at least work for Thunderbolt GPUs. > > I do not know if it is possible, but for me it looks like that check via > vga_switcheroo should be better then adding another heuristic to other > drivers. It is way simpler and more straightforward if hda_intel.c calls pci_is_thunderbolt_attached() directly, as I've suggested above. The DRM drivers call that as well and register with vga_switcheroo only if it returns false. So if hda_intel.c asked vga_switcheroo and got back a negative answer, it would never know whether it's because the DRM driver hasn't finished probing yet, or it's module is blacklisted, or whatever. > And once we would have good/reliable check for EC devices we can add it > into vga_switcheroo and all users of it could benefit. Anyway, I think > that vga_switcheroo should filter also EC GPU cards if it already > filters Thunderbolt. vga_switcheroo doesn't do the filtering, the DRM drivers themselves decice whether to register with vga_switcheroo or not. The motivation is to avoid middle layers and instead provide the DRM drivers with a library of helpers that they may call at their own discretion. See this blog post and the links therein for background info: http://blog.ffwll.ch/2016/12/midlayers-once-more-with-feeling.html Thanks, Lukas
