[2.4.31] - USB device numbering in /proc/bus/usb

[2.4.31] - USB device numbering in /proc/bus/usb

[Paul Rolland]

Hello,

I've just rebooted a machine, and the eagle ADSL modem I was using,
presented as /proc/bus/usb/002/005 in now presented as 
/proc/bus/usb/002/003 (same bus, but device ID changed from 5 to 3).

Is this an expected behavior, when running a 2.4.31 kernel ?
I would have been expecting some more stability in the numbering across
reboot, the same way IDE disks numbers are stable.

Paul

Re: [2.4.31] - USB device numbering in /proc/bus/usb

[Sergey Vlasov]

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On Tue, 23 Aug 2005 15:14:38 +0200 Paul Rolland wrote:

> I've just rebooted a machine, and the eagle ADSL modem I was using,
> presented as /proc/bus/usb/002/005 in now presented as 
> /proc/bus/usb/002/003 (same bus, but device ID changed from 5 to 3).
> 
> Is this an expected behavior, when running a 2.4.31 kernel ?

Yes.  Addresses for USB devices are assigned dynamically.  If you
disconnect the modem from USB and connect it again, its address will
change.

> I would have been expecting some more stability in the numbering across
> reboot, the same way IDE disks numbers are stable.

Use some other identifier which is stable - e.g., serial number of the
USB device (unfortunately, many devices don't have it).

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Re: [2.4.31] - USB device numbering in /proc/bus/usb

[Paul Rolland]

Hello Sergey,

> Yes.  Addresses for USB devices are assigned dynamically.  If you
> disconnect the modem from USB and connect it again, its address will
> change.

The problem I've is that nothing changed on the machine except that 
I did a reboot. Nothing (USB device) added, nothing removed, so with
a stable hardware config, USB numbering should have stayed stable, IMHO.
 
> > I would have been expecting some more stability in the 
> numbering across
> > reboot, the same way IDE disks numbers are stable.
> 
> Use some other identifier which is stable - e.g., serial number of the
> USB device (unfortunately, many devices don't have it).

Well yes, I'm going to try to convert to some other identifiers space
as this seems to be the only way to go.

Thanks for the confirmation,
Regards,
Paul
 

Re: [2.4.31] - USB device numbering in /proc/bus/usb

[Alistair John Strachan]

On Tuesday 23 August 2005 16:51, Paul Rolland wrote:
> Hello Sergey,
>
> > Yes.  Addresses for USB devices are assigned dynamically.  If you
> > disconnect the modem from USB and connect it again, its address will
> > change.
>
> The problem I've is that nothing changed on the machine except that
> I did a reboot. Nothing (USB device) added, nothing removed, so with
> a stable hardware config, USB numbering should have stayed stable, IMHO.

Basically, no it shouldn't.

>
> > > I would have been expecting some more stability in the
> >
> > numbering across
> >
> > > reboot, the same way IDE disks numbers are stable.
> >
> > Use some other identifier which is stable - e.g., serial number of the
> > USB device (unfortunately, many devices don't have it).
>
> Well yes, I'm going to try to convert to some other identifiers space
> as this seems to be the only way to go.
>
> Thanks for the confirmation,
> Regards,
> Paul

/proc/bus/usb/devices (which tells you where a device is located in the tree). 
This should work on 2.4 kernels, 2.6 kernels should be using sysfs by now.

-- 
Cheers,
Alistair.

'No sense being pessimistic, it probably wouldn't work anyway.'
Third year Computer Science undergraduate.
1F2 55 South Clerk Street, Edinburgh, UK.