Building libpciaccess generates a warning on versions of Linux in which the definition of the struct mtrr_sentry has changed to __u64:
...
  CC       linux_sysfs.lo
linux_sysfs.c: In function 'pci_device_linux_sysfs_map_range':
linux_sysfs.c:594:7: warning: format '%lx' expects argument of type 'long unsign
ed int', but argument 3 has type '__u64' [-Wformat=]
       strerror(errno), errno);
       ^
linux_sysfs.c: In function 'pci_device_linux_sysfs_unmap_range':
linux_sysfs.c:669:7: warning: format '%lx' expects argument of type 'long unsign
ed int', but argument 3 has type '__u64' [-Wformat=]
       strerror(errno), errno);
       ^

Earlier version of Linux defined this structure the same for both i386 and x86_64. More recent version changed the structure to be:

#ifdef __i386__
struct mtrr_sentry {
    unsigned long base;    /*  Base address     */
...
#else /* __i386__ */

struct mtrr_sentry {
	__u64 base;		/*  Base address     */
...
#endif /* !__i386__ */