clEnqueueReadBuffer - Enqueue commands to read from a buffer object to host memory.

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clEnqueueReadBuffer returns CL_SUCCESS if the function is executed successfully. Otherwise, it returns
       one of the following errors:

       •   CL_INVALID_COMMAND_QUEUE if command_queue is not a valid command-queue.

       •   CL_INVALID_CONTEXT if the context associated with command_queue and buffer are not the same or if the
           context associated with command_queue and events in event_wait_list are not the same.

       •   CL_INVALID_MEM_OBJECT if buffer is not a valid buffer object.

       •   CL_INVALID_VALUE if the region being read specified by (offset, size) is out of bounds or if ptr is a
           NULL value or if size is 0.

       •   CL_INVALID_EVENT_WAIT_LIST if event_wait_list is NULL and num_events_in_wait_list greater than 0, or
           event_wait_list is not NULL and num_events_in_wait_list is 0, or if event objects in event_wait_list
           are not valid events.

       •   CL_MISALIGNED_SUB_BUFFER_OFFSET if buffer is a sub-buffer object and offset specified when the
           sub-buffer object is created is not aligned to CL_DEVICE_MEM_BASE_ADDR_ALIGN value for device
           associated with queue.

       •   CL_EXEC_STATUS_ERROR_FOR_EVENTS_IN_WAIT_LIST if the read and write operations are blocking and the
           execution status of any of the events in event_wait_list is a negative integer value.

       •   CL_MEM_OBJECT_ALLOCATION_FAILURE if there is a failure to allocate memory for data store associated
           with buffer.

       •   CL_INVALID_OPERATION if clEnqueueReadBuffer is called on buffer which has been created with
           CL_MEM_HOST_WRITE_ONLY or CL_MEM_HOST_NO_ACCESS.

       •   CL_OUT_OF_RESOURCES if there is a failure to allocate resources required by the OpenCL implementation
           on the device.

       •   CL_OUT_OF_HOST_MEMORY if there is a failure to allocate resources required by the OpenCL
           implementation on the host.

       clEnqueueReadBuffer - Enqueue commands to read from a buffer object to host memory.

       cl_intclEnqueueReadBuffer(cl_command_queuecommand_queue,cl_membuffer,cl_boolblocking_read,size_toffset,size_tsize,void*ptr,cl_uintnum_events_in_wait_list,constcl_event*event_wait_list,cl_event*event);

        1. OpenCL Specification
           page 72, section 5.2.2 - Reading, Writing, Copying Buffer Objects

The Khronos Group                                  11/18/2024                          CLENQUEUEREADBUFFER(3clc)

command_queue
           Refers to the command-queue in which the read command will be queued.  command_queue and buffer must
           be created with the same OpenCL context.

       buffer
           Refers to a valid buffer object.

       blocking_read
           Indicates if the read operations are blocking or non-blocking.

           If blocking_read is CL_TRUE i.e. the read command is blocking, clEnqueueReadBuffer does not return
           until the buffer data has been read and copied into memory pointed to by ptr.

           If blocking_read is CL_FALSE i.e. the read command is non-blocking, clEnqueueReadBuffer queues a
           non-blocking read command and returns. The contents of the buffer that ptr points to cannot be used
           until the read command has completed. The event argument returns an event object which can be used to
           query the execution status of the read command. When the read command has completed, the contents of
           the buffer that ptr points to can be used by the application.

       offset
           The offset in bytes in the buffer object to read from.

       size
           The size in bytes of data being read.

       ptr
           The pointer to buffer in host memory where data is to be read into.

         event_wait_list ,   num_events_in_wait_listevent_wait_list and num_events_in_wait_list specify events that need to complete before this
           particular command can be executed. If event_wait_list is NULL, then this particular command does not
           wait on any event to complete. If event_wait_list is NULL, num_events_in_wait_list must be 0. If
           event_wait_list is not NULL, the list of events pointed to by event_wait_list must be valid and
           num_events_in_wait_list must be greater than 0. The events specified in event_wait_list act as
           synchronization points. The context associated with events in event_wait_list and command_queue must
           be the same. The memory associated with event_wait_list can be reused or freed after the function
           returns.

        event
           Returns an event object that identifies this particular read command and can be used to query or
           queue a wait for this particular command to complete.  event can be NULL in which case it will not be
           possible for the application to query the status of this command or queue a wait for this command to
           complete. If the event_wait_list and the event arguments are not NULL, the event argument should not
           refer to an element of the event_wait_list array.

clEnqueueCopyBuffer(3clc), clEnqueueWriteBuffer(3clc), clEnqueueWriteBufferRect(3clc),
       clEnqueueReadBufferRect(3clc)

OpenCLSpecification[1]