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

From: Andrei Borzenkov
Subject: Re: USB devices non-functional when chainloading Windows 7 from GRUB
Date: Mon, 16 Jan 2017 18:47:36 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1

16.01.2017 16:47, Will Thompson пишет:
> 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?

keystatus should not load USB by itself, it queries currently loaded
drivers only.

>> 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
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