title: Who calls the probe() of driver
body: <p>How does <code>probe()</code> call gets called? Who calls it? As per my understanding, <code>__init()</code> registers <code>driver</code> and then somehow <code>probe()</code> is called to <code>register</code> the device data and <code>irq</code> etc. How exactly it happens? </p>
  
  <p>I am working on touchscreen driver and its <code>__init</code> registers itself to <code>i2c driver</code>. Then probe expect <code>i2c_clien</code>t data which returns null. I want to track where it gets filled.</p>