Re: sb600/sb700 ohci experimental patch

From: Andriy Gapon <avg_at_freebsd.org>
Date: Mon, 28 Sep 2009 16:55:44 +0300
on 28/09/2009 14:48 John Baldwin said the following:
> I don't think you can do this because it is a "feature" to not disable SMM if 
> ohci(4) is not loaded so that a USB keyboard works when the USB driver isn't 
> loaded via PS/2 emulation, even when the OS is running.

Very good point.

> I am curious if we 
> really need to do the handover for each controller or if disabling it for 
> ohci0 effectively disables it for all controllers?  What do other OS's do?
> 

Don't have an answer about other OSes.
But OHCI controllers have individual "used by SMM" bits and taking over one
controller doesn't affect the bits of the other controllers - they remain set.
Not that it means that SMM code actually keeps on controlling them.

Actually, just checked - Linux also does it per controller:
http://lxr.linux.no/#linux+v2.6.31/drivers/usb/host/ohci-hcd.c#L495

-- 
Andriy Gapon
Received on Mon Sep 28 2009 - 11:55:49 UTC

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