title: How is a PCI / PCIe BAR size determined?
body: <p>I know that the base address register (BAR) in PCI configuration space defines the start location of a PCI address, but how does the size of this region get established?</p>
  
  <p>Surely this is a property of the hardware since only it knows how far into its address space it can deal. However, I cannot seem to see a BAR size field in the PCI configuration structure.</p>