u8 command, u8 length,
u8 *values)
-All these transactions return -1 on failure. The 'write' transactions
-return 0 on success; the 'read' transactions return the read value, except
-for read_block, which returns the number of values read. The block buffers
-need not be longer than 32 bytes.
+All these transactions return a negative errno value on failure. The 'write'
+transactions return 0 on success; the 'read' transactions return the read
+value, except for block transactions, which return the number of values
+read. The block buffers need not be longer than 32 bytes.
You can read the file `smbus-protocol' for more information about the
actual SMBus protocol.