Static NVIDIACTL_RDEV 

static NVIDIACTL_RDEV: AtomicU64

Identity of the RM control device, cached so the hook only rewrites responses that truly came from it: the rdev of /dev/nvidiactl, resolved once at install(). A value of 0 means it was never resolved, in which case the fd-identity gate is skipped and matching falls back to the request/size checks alone.