Linux PCIE & DMA tutorials
1. http://en.wikipedia.org/wiki/PCI_configuration_space
2. https://www.kernel.org/doc/Documentation/DMA-API-HOWTO.txt
3. http://linuxgazette.net/156/jangir.html
4. http://www.tldp.org/LDP/tlk/dd/pci.html
5. https://lkml.org/
6. http://bbs.chinaunix.net/forum.php?mod=forumdisplay&fid=227&page=1