title: how to allocate 4-8 MB aligned DMA Linux
body: <p>I"m using Fedora 14 and i"m building a driver for a PCI switch.
  for that switch I need to allocate 8MB of DMA memory (I can handle 2*4MB) but I need it aligned to memory size, for example, if its 8MB then the first 23 bits of the base address should be 0.</p>
  
  <p>how do i do that?</p>