Constant open_cl_low_level::device::UNUSABLE_DEVICE_ID

pub const UNUSABLE_DEVICE_ID: cl_device_id = 0xFFFF_FFFF as *mut usize as cl_device_id; // {pointer}

NOTE: UNUSABLE_DEVICE_ID might be osx specific? or OpenCL implementation specific? UNUSABLE_DEVICE_ID was the cl_device_id encountered on my Macbook Pro for a Radeon graphics card that becomes unavailable when powersaving mode enables. Apparently the OpenCL platform can still see the device, instead of a "legit" cl_device_id the inactive device's cl_device_id is listed as 0xFFFF_FFFF.