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

[Noboru Iwamatsu <n_iwamatsu@xxxxxxxxxxxxxx>]

Hi,

> Replugging doesn't change the usbbusname, but what about host rebooting?

usb bus number is assigned in order of the host controller registration.
This order is normally defined by the PCI device number of that host 
controller.
So, when you change the host controller's PCI device number (e.g. 
changing BIOS setting, or, adding new PCI devices), the usbbusname of 
that host controller might be changed.
> 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'.

It seems that qemu-compatible rule would be nice, but if you connect
two or more same devices (they all have same Ids), can this rule 
properly control which device is assigned to which domain?
As you pointed out, current hotplug-rule is not friendly:-)
However, originally the usbdevice naming scheme of the linux kernel is 
quite complex thing.
We might have to solve this complexity by xend or other user-space programs.

Regards,

Noboru

Sergey 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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