Fix #2348 support for CapsLock/NumLock LEDs in usb_hid

[deshipu]

No description provided.

[deshipu]

This is work in progress. Currently the report_type is always HID_REPORT_TYPE_INVALID for some reason, while it should be HID_REPORT_TYPE_OUTPUT. Possibly a bug or missing feature in the tinyusb library.

[tannewt]

I don't think this is the right API because output reports can theoretically be used for other things besides LEDs. A better api would be a circular buffer of reports that can be read through a receive_report function.

[deshipu]

I agree a more general API would be more useful, but I think it will require a considerable amount of planning. How large should the buffer be? How many entries of what size? Do we pre-allocate it always? Do we let the user choose the size that fits best their use case? How can the user make an informed decision about it?

I think that the particular combination of HID_USAGE_DESKTOP_KEYBOARD and HID_USAGE_PAGE_DESKTOP is only used for keyboard lamps, though, so we could leave it as a special case.

[tannewt]

I'd rather not add a special API because I'm going to be doing the BLE HID library soon and it'll expose this same API.

We can limit the buffer a bunch for now though. How about an 8 byte buffer that only queues 1 byte reports and return 1 byte bytestrings? When we have other reports to support we'll just make the implementation smarter.

[deshipu]

I like that. I could even live with just one one-byte report, because I only care about the most recent one. This would make the internals easy enough even for me to implement, and would have an API that could be expanded later when needed. Thanks!

[deshipu]

I tried to do a ring buffer, but it's a bit out of my depth. For now I just made a simple 1-item buffer for a single-byte report, but I updated the Python API to be what was suggested. We can change the underlying implementation later on.

[tannewt]

This implementation is totally fine. Thanks for doing it! Just a couple suggestions but then it should be good to go.

[deshipu]

I changed the interface to read_report_into, but for some reason it now stopped working. I need some more time to debug this.

[tannewt]

Thanks! Let me know when I should take another look.

[tannewt]

@deshipu any object to me closing this until it is fixed up?

[deshipu]

Sorry, I didn't have time to look into this properly, I will make a new pull request when I figure this out.