How USB's are enumerated on the XO

[Jim Gettys]

While in theory, USB devices can/should send serial numbers, that part
of the spec is honored mostly by it's absence (due to cost).

As John said, unfortunately, with USB you have to go down to the device
and see if they have something usable to distinguish devices.
                     - Jim


On Mon, 2008-06-23 at 14:07 -0400, John Watlington wrote:
> My experience is that you have to find a USB device parameter
> (serial number, MAC address, etc.) that is different between the
> two USB devices for this to ever work reliably.
> 
> wad
> 
> On Jun 23, 2008, at 10:37 AM, shivaprasad javali wrote:
> 
> > I was trying to use the port no to which the usb device is  
> > connected to differentiate between two usb devices of the same type  
> > connected in my application. For that I wanted the variant field  
> > between the two usb devices so that I can uniquely identify them.
> >
> > P.S: The output of lshal -m wasnt of much help for me.
> >
> > Thanks
> > Shivaprasad
> >
> >
> > On Mon, Jun 23, 2008 at 7:47 PM, Tomeu Vizoso  
> > <tomeu at tomeuvizoso.net> wrote:
> > 2008/6/23 shivaprasad javali <jbsp72 at gmail.com>:
> > > Hi,
> > >
> > >       I have a usb device to be used with my application which  
> > does not have
> > > any unique serial no. I noticed that when I connect two such  
> > devices to the
> > > XO , In the /proc/bus/usb/devices file the Bus for the two  
> > remains the same
> > > but the port no is different for the two. When I connect the same  
> > two
> > > devices to a normal machine running fedora core 7, Its the Bus  
> > that changes
> > > for the two and the port no remains the same.
> > >
> > >       The XO that I have is relatively old. So I wanted to know  
> > whether this
> > > is what is expected on the XO or Is it different on the later  
> > versions of
> > > the XO.
> >
> > I didn't quite understood what you are trying to do, but something
> > that may help you is to plug and unplug the usb sticks while lshal -m
> > is running. That may tell you something interesting.
> >
> > Good luck,
> >
> > Tomeu
> >
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> 
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-- 
Jim Gettys <jg at laptop.org>
One Laptop Per Child