This is xnu-11215.1.10. See this file in:
#ifndef _SYS_MEMDEV_H_
#define _SYS_MEMDEV_H_
#include <sys/appleapiopts.h>
#ifdef KERNEL_PRIVATE
#ifdef __APPLE_API_PRIVATE
void mdevinit(vm_offset_t base, unsigned int size);
#endif /* __APPLE_API_PRIVATE */
#endif /* KERNEL_PRIVATE */
#endif /* _SYS_MEMDEV_H_*/