> The case when ``length of \field{write_buf}''=0, and at the same time,
> ``length of \field{read_buf}''=0 is called not-a-read-write request
> and result for such a request is I2C device specific.

Obviously, I don't know much about the specs and their wording. Still I
wonder if we can't call it a zero length transfer? This is allowed by
the I2C standard and SMBus has even a proper name for it (SMBUS_QUICK).
From my point of view, I would not say it is device specific because
devices are expected to ACK such a message.