device with multiple interfaces - can't select HID interface or send HID command with open

trezor / cython-hidapi

:snake: Python wrapper for the HIDAPI

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device with multiple interfaces - can't select HID interface or send HID command with open #138

Closed QuadCorei8085 closed 2 years ago

QuadCorei8085 commented 2 years ago

I have a device with multiple interfaces and HID is interface #6.

When opening the device with vendor/product id the read throws an exception. When opening the device with open_path('') and using of course the correct path to the specific HID interface the read works fine.

API is missing to select an interface for the HID or is it assumed that first interface is the HID commands?

flit commented 2 years ago

What OS? Can you provide a complete descriptor dump? (e.g. with lsusb -v on Linux.)

Fwiw, pyocd uses cython-hidapi for CMSIS-DAPv1 devices that invariably have the HID interface being number 2 or higher, or even multiple HID interfaces. hidapi does sometimes have issues with some devices with multiple HID interfaces on certain OSes (root cause is unclear), but you seem to have a single-HID-interface device.

prusnak commented 2 years ago

ISTM the underlying API written in C does not provide any other option just:

opening by vendor_id/product_id via hid_open
opening by path via hid_open_path

I don't think we can do more here.