Re: [Qemu-devel] USB Hostport Differences

[Hans de Goede <hdegoede@redhat.com>]

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