quoted

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?

Maybe that.

I'd prefer it.

quoted

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.

Actually we should skip the last line from my diff, i.e. completely
drop "and result for such a request is I2C device specific".

Sounds good.

The device (host in virtio spec terminology) still needs to return
success/failure as it does for other requests. Nothing special here.

Ack.