Function report_is_valid 

pub fn report_is_valid(report: &[u8; 8]) -> bool

Is an 8-byte HID boot report real device data, or the all-0xff signature of a failed/stale DMA read (a device that vanished mid-transaction, or a buffer the controller never wrote)? Returns false only for an all-0xff report. This is the universal garbage check - safe for both keyboards and mice (a real mouse won’t send all-0xff; a keyboard never does) - which a driver uses to count a wedged endpoint toward disconnect and re-enumerate. (The keyboard decoder additionally rejects any report whose reserved byte 1 ≠ 0, a stricter check that only makes sense for keyboards.)