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Re: [Qemu-devel] Bus number and address changes after usb_add?

From: Lonnie Mendez
Subject: Re: [Qemu-devel] Bus number and address changes after usb_add?
Date: Wed, 06 Dec 2006 22:25:23 -0600

On Thu, 2006-12-07 at 12:18 +0800, Yu, Xiaoyang wrote:
> After add a USB device by “usb_add”, I can view it by “info usb”. It
> shows the bus number and address.
> As shown in vl.c, it seems that usb_info() is called when issue “info
> usb”, and usb_device_add() is called when issue “usb_add”. 
> But if I add call to usb_info() in the end of usb_device_add(), it
> always show the bus number and address as “0.0”, which can be
> different from the output of “usb_add”.
> So it seems like the bus number and address of a USB device changed
> some time after “usb_add”. Does anyone know why it changes? Thanks in
> advance!

The address you see with the monitor command "info usb" is the address
all usb devices start out with when connected to the guest.  The guest
os will later assign the device an address on bus 0 (the uhci controller
on the i386 system target) after it does things like fetch the device
descriptor, configuration, etc.  iirc linux will first assign a device
an address unlike windows which queries for the configuration
information before an address is assigned.

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