## io_done_queue_wait

System Trap - Wait on an io_done_queue kernel object.

### SYNOPSIS

    kern_return_t	io_done_queue_wait
    		(mach_port_t             queue,
    		io_done_result_t       *result);

### PARAMETERS

queue
  [in io-done-queue send right] The port referencing the io_done_queue to be destroyed.

result
  [out structure] The data structure to be filled in with the completion status of the I/O operation.

### DESCRIPTION

The io_done_queue_wait interface is called to obtain the results of a previously requested asynchronous I/O operation. For each io_done_queue_wait invocation, the status of one I/O request is returned. If there are no pending I/O completions, io_done_queue_wait blocks in the kernel on the address of the completion queue. The mKernel, from interrupt context, enqueues (in FIFO order) completions (struct io_done_result's) on the completion queue and posts a wakeup on the queue for each I/O completion. Completion processing previously done by the mKernel io_done thread is now done by the task thread when it awakens.

### RETURN VALUES

KERN_TERMINATED
  Stale io_done_queue handle.

KERN_INVALID_ARGUMENT
  Invalid queue parameter.

KERN_INVALID_ARGUMENT
  The result parameter is a bad address.

### RELATED INFORMATION

Functions: io_done_queue_create, io_done_queue_wait, device_read_async, device_read_async_inband, device_read_overwrite_async, device_write_async, device_write_async_inband.