PCI Express BAR memory mapping basic understanding

Question

I am trying to understand how PCI Express works so i can write a windows driver that can read and write to a custom PCI Express device with no on-board memory.

I underst

Answer 1

clarification for your doubts/questions is here.

1> There are many devices thats sits on BUS like PCI which sees Memeory in terms that are different from a Physical address, those are called bus addresses. For example if you are initaiating DMA from a device sitting on bus to Main memory of system then destination address should be corresponding bus address of same physical address in Memmory

2> BARS gets populated at the time of enumeration, in a typical PC it is at boot time when your PCI aware frimware enumerate PCI devices presents on slot and allocate addresses and size to BARS.

3> yes you can use both DMA initiated or CPU initiated operations on these BARS.

-- flyinghigh