[Libvir] Re; virDomainBlockStats

Hi, I've a number of servers running XEN and am trying to write some code to monitor them through libvirt. (Xeon/Dual Core/Ubuntu Gutsy/Xen 3.1) All was going well until I got to virDomainBlockStats and it simply refused to accept my coding .. My solution (the code now works) is to change the following; src/stats_linux.c: #ifndef XENVBD_MAJOR #define XENVBD_MAJOR 3 // <--- I changed this! /*#define XENVBD_MAJOR 202*/ #endif device = XENVBD_MAJOR * 256 + 1 + minor /* * 16 */; <-- this too! It now seems to give me some meaningful numbers without feeding my any error messages. Can anyone tell me "why" I needed to do this? I'm using "xvda" as the device path .. tried every other device name I could think of with out any good results ... ????? tia Gareth.