Constant NV_ESC_RM_CONTROL 

const NV_ESC_RM_CONTROL: c_ulong = 0x2A;

The ioctl command number (_IOC_NR, bits 0-7) that identifies the RM control escape — the low byte the request gate keys on to recognize NV_RM_CONTROL_REQUEST. Kept as a named constant only for documentation and the ioc_nr_extracts_low_byte unit test, hence #[allow(dead_code)].