> As far as I can tell from the source code, the dib0700 simply isn't able 
> to handle 0-length reads.  Should the dib0700_ctrl_rd() routine be 
> changed simply to return 0 in such cases?

The adapter (I assume the one in dvb-usb-i2c.c) should populate an
i2c_adapter_quirks struct with I2C_AQ_NO_ZERO_LEN and then the core will
bail out for you.