stop, read, and write methods. Some controllers don't implement these
individual operations and have only a transfer method. In that case, we
should return an indication that the device is present but doesn't support
the method, as opposed to the kobj default error ENXIO which makes it
look like the whole device is missing. Userland tools such as i2c(8) can
use the differing return values to switch between the two different i2c
IO mechanisms.
5623dee899