illumos gate

lm75(7D) allows setting of various temperatures, in a somewhat annoying format:
See http://www.datasheetcatalog.org/datasheet/nationalsemiconductor/DS012658.PDF section 1.4.

Basically, we have 16bits: bit 15 is sign, bits 14-6 are temperature, bits 5-0 are ignored.
The temperature encoding doesn't actually matter, but the one bit of temperature in the 2nd byte is half a degree.

When we come to do this we do:

    i2c_tran_pointer->i2c_wbuf[1] = (temp16 >> 1);
    i2c_tran_pointer->i2c_wbuf[2] = ((temp16 & 0xFE) << 7);

The mask on the second line removes the only bit we actually care about, losing us half a degree of temperature.