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vpelletier / python-functionfs

Pythonic API for linux's functionfs
GNU General Public License v3.0
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Multiple Interface Descriptor #14

Closed colabi closed 3 years ago

colabi commented 4 years ago

Great Project. I've brought up the interface to simulate a medical device in development. However, I'm having trouble understanding if creating a configuration with multiple interfaces (and alternate interfaces) is supported. Is this something that can be made to work?

vpelletier commented 4 years ago

You need to overload the onSetup method to handle the SET_INTERFACE request, keep track of the latest selected one and alter the behaviour of the endpoints based on that value. You will probably want to keep calling super(YourClass, self).onSetup(...) when your code does not recognises the request, to avoid having to reimplement everything from Function.onSetup. If I remember the USB spec correctly, you also need to reset the selected alternate setting to the default one when onEnable is called (which IIRC happens when hosts issues a SET_CONFIGURATION request).

And of course, you should populate the descriptors accordingly, so the host driver knows the alternate setting exists.

colabi commented 4 years ago

Fantastic. Thank you for the guidance. I'll attempt the modifications and post any success!