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Re: [Qemu-devel] USB Hostport Differences


From: Hans de Goede
Subject: Re: [Qemu-devel] USB Hostport Differences
Date: Sun, 10 Jun 2012 14:02:53 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0

Hi,

On 06/10/2012 12:51 PM, Erik Rull wrote:
Hans de Goede wrote:
Hi,

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

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"

Regards,

Hans

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
controller,
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
actually
a hub between the root hub and the ports.

Regards,

Hans


Hi Hans,

thanks for the explanation - so I will try to find out which way of USB 
handling is given on the current system and then add the correct hostport 
filters.

Is there an easier way of finding this kind of architecture automatically 
beside grep'ing for such a Hub?

Not that I know of I'm afraid.

Regards,

Hans



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