We use it to open endpoints as they are used. Fetching the descriptor
as needed can cause issues with devices that we're expecting a control
packet while another transaction was ongoing. Specifically, a usb
thumb drive didn't expect a control transaction while doing a SCSI
transaction.
This PR also aborts transactions on timeout or ctrl-c interrupt. It
doesn't always recover though...
1. Raise an exception when creating a USB device when host isn't
initialized.
2. Mark RP2040 dtcm_bss as NOLOAD since it doesn't need to be
loaded (just zeroed.)
3. Fix submodule location for ulab to Jeff's copy.
This allows you to list and explore connected USB devices. It
only stubs out the methods to communicate to endpoints. That will
come in a follow up once TinyUSB has it. (It's in progress.)
Related to #5986
Jeff Epler
Dan Halbert
Scott Shawcroft