HelenOS sources

IPC_PHONE_FREE    200 kernel/generic/src/ipc/ipc.c 	phone->state = IPC_PHONE_FREE;
IPC_PHONE_FREE    466 kernel/generic/src/ipc/ipc.c 	if (phone->state == IPC_PHONE_FREE ||
IPC_PHONE_FREE    932 kernel/generic/src/ipc/ipc.c 	if (phone->state != IPC_PHONE_FREE) {