Example of bit subdivision of an id of a XenTrace event

xentrace_event_id.c

#include <stdio.h>

int main() {
    // TRC_TRACE_CPU_CHANGE
    unsigned cpu_change = 0x0001f003;

    struct {
        unsigned minor:12,
                sub:4,
                main:12,
                unused:4;
    } *evt = (typeof(evt)) &cpu_change;

    printf("0x%01x 0x%03x 0x%01x 0x%03x\n", evt->unused, evt->main, evt->sub, evt->minor);
        // "0x0    0x001  0xf    0x003 \n"

    return 0;
}