Re: Walking the USB tree?

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On Thu, 30 Jun 2011, Greg KH wrote:

> On Thu, Jun 30, 2011 at 01:26:37PM -0700, Sarah Sharp wrote:
> > Hi Alan,
> > 
> > In an upcoming patchset, I'm going to need to walk the USB tree in the
> > xHCI driver in order to gather some information during a device
> > configuration or alt setting change.  Is there anything stopping the USB
> > tree from changing while this operation is in progress?
> 
> Not if you use the proper "walk the bus for all devices" functions that
> the driver core provides.  Use them and you should be fine, right?

bus_for_each_dev() is always a possibility.  It doesn't tell you the
tree ordering, and it will include all device structures registered to
the usb_bus_type (including usb_interfaces as well as usb_devices, and
also including devices below non-xHCI controllers).  If Sarah is okay
with these limitations, it's easier than explicitly going through the
tree by hand.

Alan Stern

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