Creates a pipe object.

cl_mem clCreatePipe(cl_context context,
                    cl_mem_flags flags,
                    cl_uint pipe_packet_size,
                    cl_uint pipe_max_packets,
                    const cl_pipe_properties * properties,
                    cl_int *errcode_ret)

Parameters

context

A valid OpenCL context used to create the pipe object.

flags

A bit-field that is used to specify allocation and usage information such as the memory arena that should be used to allocate the pipe object and how it will be used. The table below describes the possible values for flags. Only CL_MEM_READ_ONLY, CL_MEM_WRITE_ONLY, CL_MEM_READ_WRITE, and CL_MEM_HOST_NO_ACCESS can be specified when creating a pipe object. If value specified for flags is 0, the default is used which is CL_MEM_READ_WRITE | CL_MEM_HOST_NO_ACCESS.

cl_mem_flags Description

CL_MEM_READ_WRITE

This flag specifies that the memory object will be read and written by a kernel. This is the default.

CL_MEM_WRITE_ONLY

This flag specifies that the memory object will be written but not read by a kernel.

Reading from a buffer or image object created with CL_MEM_WRITE_ONLY inside a kernel is undefined.

CL_MEM_READ_WRITE and CL_MEM_WRITE_ONLY are mutually exclusive.

CL_MEM_READ_ONLY

This flag specifies that the memory object is a read-only memory object when used inside a kernel.

Writing to a buffer or image object created with CL_MEM_READ_ONLY inside a kernel is undefined.

CL_MEM_READ_WRITE or CL_MEM_WRITE_ONLY and CL_MEM_READ_ONLY are mutually exclusive.

CL_MEM_USE_HOST_PTR

This flag is valid only if host_ptr is not NULL. If specified, it indicates that the application wants the OpenCL implementation to use memory referenced by host_ptr as the storage bits for the memory object.

OpenCL implementations are allowed to cache the buffer contents pointed to by host_ptr in device memory. This cached copy can be used when kernels are executed on a device.

The result of OpenCL commands that operate on multiple buffer objects created with the same host_ptr or overlapping host regions is considered to be undefined.

CL_MEM_ALLOC_HOST_PTR

This flag specifies that the application wants the OpenCL implementation to allocate memory from host accessible memory.

CL_MEM_ALLOC_HOST_PTR and CL_MEM_USE_HOST_PTR are mutually exclusive.

CL_MEM_COPY_HOST_PTR

This flag is valid only if host_ptr is not NULL. If specified, it indicates that the application wants the OpenCL implementation to allocate memory for the memory object and copy the data from memory referenced by host_ptr.

CL_MEM_COPY_HOST_PTR and CL_MEM_USE_HOST_PTR are mutually exclusive.

CL_MEM_COPY_HOST_PTR can be used with CL_MEM_ALLOC_HOST_PTR to initialize the contents of the cl_mem object allocated using host-accessible (e.g. PCIe) memory.

CL_MEM_HOST_WRITE_ONLY

This flag specifies that the host will only write to the memory object (using OpenCL APIs that enqueue a write or a map for write). This can be used to optimize write access from the host (e.g. enable write-combined allocations for memory objects for devices that communicate with the host over a system bus such as PCIe).

CL_MEM_HOST_READ_ONLY

This flag specifies that the host will only read the memory object (using OpenCL APIs that enqueue a read or a map for read).

CL_MEM_HOST_WRITE_ONLY and CL_MEM_HOST_READ_ONLY are mutually exclusive.

CL_MEM_HOST_NO_ACCESS

This flag specifies that the host will not read or write the memory object.

CL_MEM_HOST_WRITE_ONLY or CL_MEM_HOST_READ_ONLY and CL_MEM_HOST_NO_ACCESS are mutually exclusive.

pipe_packet_size

Size in bytes of a pipe packet.

pipe_max_packets

Specifies the pipe capacity by specifying the maximum number of packets the pipe can hold.

properties

A list of properties for the pipe and their corresponding values. Each property name is immediately followed by the corresponding desired value. The list is terminated with 0. In OpenCL 2.0, properties must be NULL.

errcode_ret

Will return an appropriate error code. If errcode_ret is NULL, no error code is returned.

Notes

Pipes follow the same memory consistency model as defined for buffer and image objects. The pipe state i.e. contents of the pipe across kernel executions (on the same or different devices) is enforced at a synchronization point.

Errors

clCreatePipe returns a valid non-zero pipe object and errcode_ret is set to CL_SUCCESS if the pipe object is created successfully. Otherwise, it returns a NULL value with one of the following error values returned in errcode_ret:

  • CL_INVALID_CONTEXT if context is not a valid context.

  • CL_INVALID_VALUE if values specified in flags are not as defined above.

  • CL_INVALID_VALUE if properties is not NULL.

  • CL_INVALID_PIPE_SIZE if pipe_packet_size is 0 or the pipe_packet_size exceeds CL_DEVICE_PIPE_MAX_PACKET_SIZE value specified in table 4.3 (see clGetDeviceInfo) for all devices in context or if pipe_max_packets is 0.

  • CL_MEM_OBJECT_ALLOCATION_FAILURE if there is a failure to allocate memory for the pipe 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.

Also see

Specification