Re: [Xen-devel] [PVUSB] usbbusname is changing after rebooting

[Sergey Tovpeko <tsv.devel@xxxxxxxxx>]

Hi, Neobiker!

Usbbusnumber is the combination of 'usb host controller' number and 'hub 
port' number.
I'm not USB expert, but as i understood, 'USB host controller' number is 
assigned during computer booting by 'usb core driver'. And on my machine 
I see that the same USB host controller may get different number on 
rebooting. I suppose here is a race between controllers on device 
probing process. But i don't have any technical referencies of this.
It's my notion only. And, perhaps it's the question of PCI devices 
detection process, because USB host controller is part of a PCI device.
And, in your case, you have to different usb host controllers and they 
have got different numbers.
UHCI is the USB 1.0 standard  with low data throughput, this enough for 
printers. USB stick requires more  speed for data transfer, and USB 2.0 
(EHCI controller) is granted for it.
I suppose, you're lucky and you have the stable numbers for each 
controllers.
Sergey.
> Hi Sergey,
>
> i thought i had trouble with that too, until i figured out that the USB-Bus
> only seemed to have changed, when i changed the connected Device e.g. from
> USB-Printer to USB-Stick. The Printer uses the UHCI Controller (3-1), versus
> the USB-Stick connected to the EHCI Controller (5-1). Besides this the USB
> ports are stable on my Debian Lenny System. 
>
> So in my summary, the USB-Bus don't changes if you don't switch from UHCI to
> EHCI according to the connected device.
>
> regards 
> Neobiker 
>
> Sergey-53 wrote:
>   
> > Hello, all!
> > Hello, Noboru!
> >
> > Hotplug rule for PVUSB consists of
> > <usbbusname>:<domid>:<vusb number>:<port number>
> >
> > I noticed that usbbusname sometimes changes from time to time after host 
> > rebooting.
> > For example, yesterday i had it as "6-1", today it is "2-1".
> >
> > I saw the topic about usbbusname on replugging.
> > http://lists.xensource.com/archives/html/xen-devel/2009-04/msg00400.html
> > Replugging doesn't change the usbbusname, but what about host rebooting?
> >
> >  I suppose, usb bus number is assigned during booting and may vary each 
> > time.
> > To identify usb device correctly i have to see dmesg after rebooting. 
> > It's quite inconvinient, imho.
> > What do you think about another method of USB naming like 
> > VendorId:ProductId of usb devices to be grabbed by domU?
> > It seems that HVM guests use this method by means of the parameter 
> > 'usbdevice'.
> > Thank you.
> >
> > Sergey.
> >
> >
> > --
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> >
> >
> >     
>   

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