usb: preserve error when doing request

[aokblast]

Summary

Currently, USB request not distinguished different error and always return EIO.
However, some error are recoverable or ignorable in userspace.
Therefore, we preserve the meaning of different error to userspace then
allow userspace to decide how to use the return error.

For example, when host required a vendor defined descriptor but the device refused to do so. According to the XHCI protocol. it should return USB_ERR_STALLED. And this kind of error is definitely ignorable.

Sponsored by: The FreeBSD Foundation

[aokblast]

Minor updates

[kevans]

lib/libusb/libusb10_io.c

505

This seems to have accidentally conflated error namespaces, which would have coincidentally worked since the values are the same here.

507

Not strictly necessary, but IMO nice to call it out as a reminder. I'd maybe pair it with an explanation at the final return down below of where you might expect err > 0 or an assertion if that just can't happen.

lib/libusb/libusb20_ugen20.c

799

style(9)

sys/dev/usb/usb_generic.c

895

Maybe paranoid, but I'd probably recommend:

MPASS(error < nitems(usb_error_to_errno);