I2C_DEBUG
I2C_DEBUG(kprintf("%c ",noack?'-':'+'));
I2C_DEBUG(kprintf("w%02x",(int)data));
I2C_DEBUG(kprintf("r%02x%c ",(int)data,last?'-':'+'));
I2C_DEBUG(kprintf("<"));
I2C_DEBUG(kprintf(">"));
I2C_DEBUG(kprintf("\n"));