Function IODataQueueEnqueue 

pub unsafe extern "C-unwind" fn IODataQueueEnqueue(
    data_queue: *mut IODataQueueMemory,
    data: *mut c_void,
    data_size: u32,
) -> IOReturn

Enqueues a new entry on the queue.

This method adds a new data entry of dataSize to the queue. It sets the size parameter of the entry pointed to by the tail value and copies the memory pointed to by the data parameter in place in the queue. Once that is done, it moves the tail to the next available location. When attempting to add a new entry towards the end of the queue and there isn’t enough space at the end, it wraps back to the beginning.
If the queue is empty when a new entry is added, the port specified in IODataQueueSetNotificationPort will be used to send a message to the client process that data is now available.
Please note that using this method without mapped memory create from an IOSharedDataQueue will result in undefined behavior.

Parameter dataQueue: The IODataQueueMemory region mapped from the kernel created from an IOSharedDataQueue.

Parameter data: Pointer to the data to be added to the queue.

Parameter dataSize: Size of the data pointed to by data.

Returns: Returns kIOReturnSuccess on success. Other return values possible are: kIOReturnOverrun - queue is full.

Safety

• data_queue must be a valid pointer.
• data must be a valid pointer.