Re: USB devices non-functional when chainloading Windows 7 from GRUB

[Andrei Borzenkov]

13.01.2017 13:52, Will Thompson пишет:
> Hi,
> 
> A user has reported that, after they set up Endless OS to dual-boot with
> Windows 7, their keyboard and mouse no longer work in Windows, though they
> work fine in our Linux distro. This is a BIOS system. There's nothing
> particularly fancy in our GRUB 2 config for the Windows boot path: we just
> chainload the bootable partition. lsusb output shows that they have a USB 3
> controller (which is not supported out of the box in Windows 7, AIUI) but
> that their keyboard and mouse are attached to a USB 2 controller.
> 
> There are a few reports around the internet of this issue. One thread[1] I
> found suggests that disabling Windows' driver verification helps; another
> thread[2] suggests installing a USB controller driver update. But in both
> cases, the controller worked fine when GRUB was not part of the boot path,
> so I'm wondering whether GRUB is leaving the controllers in some different
> state.
> 
> Have you heard reports of this issue?

No

> Any idea what's going on?
>


Not really. GRUB does not touch USB at all unless explicitly told to do
so by switching to native drivers or attempting to use USB
keyboard/mouse. It is possible that BIOS puts USB in some state that
*does* require payload to do something.

There were discussions regarding USB handoff for xHCI. As you have USB3
this may be related. Let me look ... OK, subjects are

EHCI handoff & AMI BIOS EHCI Handoff support.​
[PATCH]: xHCI/EHCI - Windows - BIOS bug interaction

and more recent

xHCI driver

although the second one deals with opposite situation - keyboard does
not work in GRUB after reboot from Windows.