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Re: [Qemu-devel] USB Hostport Differences

From: Hans de Goede
Subject: Re: [Qemu-devel] USB Hostport Differences
Date: Fri, 08 Jun 2012 23:32:33 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0


On 06/08/2012 10:56 PM, Erik Rull wrote:
Hans de Goede wrote:

On 06/08/2012 06:33 PM, Erik Rull wrote:
Hi all,

when assigning USB host devices to a guest using the hostport option,
there seem to be different formats, when calling info usbhost:

- On my vanilla kernel linux there is a hostport format e.g. "1.5" or "1.2"
- On my Debian 6.0 full blown linux there is a hostport format "2" or
"4", that means, there are no dots and only one number

Hmm, is this on the same machine, with the usb devices hooked up the same
way? Normally these differences come
from there being hubs in the chain, ie "2" or "4" indicate devices plugged
directly into a root hub,
"1.5" and "1.2" mean devices plugged into a hub, which itself is plugged
into root port "1"



No it's on different machines - first with Intel Hardware, second with AMD Hardware. I 
have no hubs attached, I use the ports that are offered directly on the mainboard (EPIC 
Nano Connectors / ATX rear side panel). On all other Intel systems I see the same effect 
with the "1.x" ports. Only the AMD system shows the single numbers.

Those would be sandy bridge or newer Intel machines then, these no longer have
an EHCI usb controller + UHCI companion controllers, but only an EHCI 
so the root ports are USB-2 only. In order for USB-1 devices to still work the
chipset has an integrated USB-2 hub (which can handle USB-1 ports), of you do
lsusb you should see something like this in there:

Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub

Which is why you get the 1.x for the motherboard ports, because there is 
a hub between the root hub and the ports.



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