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

[Will Thompson]

On 14/01/17 08:03, Andrei Borzenkov wrote:
> 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.

Does "attempting to use USB keyboard" include invoking "keystatus"? We 
don't explicitly load "usb" or "usb_keyboard" so my assumption is that 
this is going through i386/pc/console rather than usb_keyboard, but 
perhaps I'm wrong?

> 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.

Thanks, these are some useful pointers. I don't have physical access to 
the affected machine so we are at the mercy of the user when it comes to 
trying possible workarounds. I'll report back if we find anything 
actionable, and/or whether the user can shed any light on the exact 
combination of devices and BIOS settings which lead to this situation.

– Will