Re: hub port power control vs. physical disconnect/connect

[Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>]

On Wed, 12 Dec 2007, Vlado Handziski wrote:

> On Dec 12, 2007 4:20 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> 
> > The USB stack doesn't remove a device until it gets a disconnect
> > message from the device's hub.  When you turn off the port power the
> > hub doesn't send any disconnect messages, so the kernel doesn't realize
> > the device is gone.
> >
> > Currently there is no way for you to force this behavior (and there is
> > no way to call usb_disconnect from userspace).  You can come close by
> > unbinding the device's driver.  For example, if the device's sysfs ID
> > was 1-2.3 you would do:
> >
> >        echo -n 1-2.3 >/sys/bus/usb/drivers/usb/unbind
> >
> > That won't remove the device structure but it will make the structure
> > almost unusable.
> >
> 
> Yes, we are already doing that (as shown in case 2 in the log at the end of
> the original message). I was hoping that there is something more that can be
> done that would either remove the device completely or at least export
> somehow the info to sysfs that the structure below this devce path is stale.

Right now there isn't anything like that.  It could be added if people 
really want it.

Alan Stern


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