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