C Specification

To create a new buffer object (referred to as a sub-buffer object) from an existing buffer object, call the function

cl_mem clCreateSubBuffer(
    cl_mem buffer,
    cl_mem_flags flags,
    cl_buffer_create_type buffer_create_type,
    const void* buffer_create_info,
    cl_int* errcode_ret);
clCreateSubBuffer is missing before version 1.1.

Parameters

  • buffer must be a valid buffer object and cannot be a sub-buffer object.

  • flags is a bit-field that is used to specify allocation and usage information about the sub-buffer memory object being created and is described in the Memory Flags table. If the CL_MEM_READ_WRITE, CL_MEM_READ_ONLY, or CL_MEM_WRITE_ONLY values are not specified in flags, they are inherited from the corresponding memory access qualifiers associated with buffer. The CL_MEM_USE_HOST_PTR, CL_MEM_ALLOC_HOST_PTR, and CL_MEM_COPY_HOST_PTR values cannot be specified in flags but are inherited from the corresponding memory access qualifiers associated with buffer. If CL_MEM_COPY_HOST_PTR is specified in the memory access qualifier values associated with buffer it does not imply any additional copies when the sub-buffer is created from buffer. If the CL_MEM_HOST_WRITE_ONLY, CL_MEM_HOST_READ_ONLY, or CL_MEM_HOST_NO_ACCESS values are not specified in flags, they are inherited from the corresponding memory access qualifiers associated with buffer.

  • buffer_create_type and buffer_create_info describe the type of buffer object to be created. The list of supported values for buffer_create_type and corresponding descriptor that buffer_create_info points to is described in the SubBuffer Attributes table.

Description

Table 1. List of supported buffer creation types by clCreateSubBuffer
Buffer Creation Type Description

CL_BUFFER_CREATE_TYPE_REGION

missing before version 1.1.

Create a buffer object that represents a specific region in buffer.

buffer_create_info is a pointer to a cl_buffer_region structure specifying a region of the buffer.

If buffer is created with CL_MEM_USE_HOST_PTR, the host_ptr associated with the buffer object returned is host_ptr + origin.

The buffer object returned references the data store allocated for buffer and points to the region specified by buffer_create_info in this data store.

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

  • CL_INVALID_MEM_OBJECT if buffer is not a valid buffer object or is a sub-buffer object.

  • CL_INVALID_VALUE if buffer was created with CL_MEM_WRITE_ONLY and flags specifies CL_MEM_READ_WRITE or CL_MEM_READ_ONLY, or if buffer was created with CL_MEM_READ_ONLY and flags specifies CL_MEM_READ_WRITE or CL_MEM_WRITE_ONLY, or if flags specifies CL_MEM_USE_HOST_PTR or CL_MEM_ALLOC_HOST_PTR or CL_MEM_COPY_HOST_PTR.

  • CL_INVALID_VALUE if buffer was created with CL_MEM_HOST_WRITE_ONLY and flags specify CL_MEM_HOST_READ_ONLY, or if buffer was created with CL_MEM_HOST_READ_ONLY and flags specify CL_MEM_HOST_WRITE_ONLY, or if buffer was created with CL_MEM_HOST_NO_ACCESS and flags specify CL_MEM_HOST_READ_ONLY or CL_MEM_HOST_WRITE_ONLY.

  • CL_INVALID_VALUE if the value specified in buffer_create_type is not valid.

  • CL_INVALID_VALUE if value(s) specified in buffer_create_info (for a given buffer_create_type) is not valid or if buffer_create_info is NULL.

  • CL_MEM_OBJECT_ALLOCATION_FAILURE if there is a failure to allocate memory for sub-buffer object.

  • 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.

  • CL_INVALID_VALUE if the region specified by the cl_buffer_region structure passed in buffer_create_info is out of bounds in buffer.

  • CL_INVALID_BUFFER_SIZE if the size field of the cl_buffer_region structure passed in buffer_create_info is 0.

  • CL_MISALIGNED_SUB_BUFFER_OFFSET if there are no devices in context associated with buffer for which the origin field of the cl_buffer_region structure passed in buffer_create_info is aligned to the CL_DEVICE_MEM_BASE_ADDR_ALIGN value.

Concurrent reading from, writing to and copying between both a buffer object and its sub-buffer object(s) is undefined. Concurrent reading from, writing to and copying between overlapping sub-buffer objects created with the same buffer object is undefined. Only reading from both a buffer object and its sub-buffer objects or reading from multiple overlapping sub-buffer objects is defined.

See Also

Document Notes

For more information, see the OpenCL Specification

This page is extracted from the OpenCL Specification. Fixes and changes should be made to the Specification, not directly.

Copyright 2014-2023 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0