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RE: Missing USB devices.


From: Melki Christian (consultant)
Subject: RE: Missing USB devices.
Date: Wed, 28 Aug 2013 06:59:01 +0000

Ales,

I'm thinking of the EHCI hand-over. In the case of EHCI handover beeing 
successful within the timeout, you never clear the USBLEGCTLSTS register 
(SMI's). You do that in the other cases however. Why? I can not think of any 
case of a successful handover with SMI's still enabled. To what purpose? A 
buggy BIOS would maybe act upon such stuff? Maybe thats a case for lost devices 
etc?
Also, I've been toying with the black magic EHCI hand-back. I've gotten it to 
work for some machines. The problem with GRUB and USB is that if you enable USB 
you have no more control over USB in case a OS needs input before loading it's 
own USB stack. Do you have any experience with this? Could we make such code 
execution optional on environment etc (because hand back is even more buggy 
than everything else.. :)) Maybe users can use it in corner cases when they 
need USB-input with usb-support in GRUB... if it'll work on their hardware that 
is.

Regards,
Christian 



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