title: functionality of pci_set_dma_mask
body: <p>I am bit confused for pci_set_dma_mask. So can somebody explain me what exactly happens in below code.</p>
  
  <pre><code>#define DMA_64BIT_MASK DMA_BIT_MASK(64)
  pci_set_dma_mask(dev, DMA_64BIT_MASK)
  </code></pre>
  
  <p>Regards
  Rabinarayan</p>