There was a discussion about this a while back, but I can't locate the 
messages in the archives or remember what the objections were.

Would there be a problem if the choose_configuration routine was changed
to avoid configs that exceed the parent hub's power budget?  This problem
was just reported on linux-usb-users: The device has both a high-power and
a low-power config, the high-power one is chosen because it is listed
first, and it causes an overcurrent condition (taking down two or three
other USB devices along with it) when plugged into a low-power hub.


On a more theoretical note, it would be logical to move the configuration
selection and installation code from where it is now (under
usb_new_device) into the usb_generic probe routine.  In a sense, that's
the main function carried out when a new device is discovered.  And now
that there is code to deconfigure devices when they are unbound from
usb_generic, for symmetry they should be reconfigured when they are
rebound.

Practically speaking, this may not be worthwhile.  I don't expect people 
to go around unbinding and rebinding usb_generic very often.  Moving the 
code like that would end up accomplishing little more than increasing the 
stack usage.  Greg, what do you think?

(Oh yes, if we proceed this way then at some point usb_device_match should
be changed so that usb_generic always matches against devices and other
drivers only match against interfaces.  Right now it doesn't take account 
of the possibility that usb_generic might be unbound or reprobed.)

Alan Stern



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