Yes, a configuration change is:
1. Lock device
2. Disconnect all interfaces
3. Send control message
4. Unlock device
5. Probe all the device's interfaces

To a driver changing a configuration is an unplug, replug cycle.

Make that probe()/disconnect() ... :)


Something I want (eventually) to see between steps 2 & 4 is
notifying the hcd to clear each endpoint's configuration data.
That state is known to hardware (OHCI and EHCI) so changing it
needs hardware synchronization.

The same problem comes up with (re)setting an interface to
some altsetting.  There's no probe/disconnect relevant there
since the interface doesn't go away, but the hardware does
need to clear out its state.

- Dave







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