clCreateContextFromType

Create an OpenCL context from a device type that identifies the specific device(s) to use.

cl_context clCreateContextFromType ( const cl_context_properties  *properties,
  cl_device_type  device_type,
  void  (CL_CALLBACK *pfn_notify) (const char *errinfo,
  const void  *private_info,
  size_t  cb,
  void  *user_data),
  void  *user_data,
  cl_int  *errcode_ret)

Parameters

properties

Specifies a list of context property names and their corresponding values. Each property name is immediately followed by the corresponding desired value. The list of supported properties is described in the table below. properties can also be NULL in which case the platform that is selected is implementation-defined.

If the cl_khr_gl_sharing extension is supported, properties points to an attribute list whose format and valid contents are identical to the properties argument of clCreateContext which is: properties specifies a list of context property names and their corresponding values. Each property name is immediately followed by the corresponding desired value. The list is terminated with 0. The list of supported properties is described in the table below. properties can be NULL in which case the platform that is selected is implementation-defined.

cl_context_properties enum Property value Description
CL_CONTEXT_PLATFORM cl_platform_id Specifies the platform to use.
CL_CONTEXT_INTEROP_USER_SYNC cl_bool Specifies whether the user is responsible for synchronization between OpenCL and other APIs. Please refer to the specific sections in the OpenCL 1.2 extension specification that describe sharing with other APIs for restrictions on using this flag. If CL_CONTEXT_INTEROP_USER_SYNC is not specified, a default of CL_FALSE is assumed.
CL_CONTEXT_D3D10_DEVICE_KHR ID3D10Device * Specifies the ID3D10Device * to use for Direct3D 10 interoperability. The default value is NULL (applies if the extension cl_khr_d3d10_sharing is supported)
CL_CONTEXT_ADAPTER_D3D9_KHR IDirect3DDevice9 * Specifies an IDirect3DDevice9 to use for D3D9 intero (applies if the cl_khr_dx9_media_sharing extension is supported)
CL_CONTEXT_ADAPTER_D3D9EX_KHR IDirect3DDeviceEx* Specifies an IDirect3DDevice9Ex to use for D3D9 interop (applies if the cl_khr_dx9_media_sharing extension is supported)
CL_CONTEXT_ADAPTER_DXVA_KHR IDXVAHD_Device * Specifies an IDXVAHD_Device to use for DXVA interop (applies if the cl_khr_dx9_media_sharing extension is supported)
CL_GL_CONTEXT_KHR 0, OpenGL context handle OpenGL context to associated the OpenCL context with (available if the cl_khr_gl_sharing extension is enabled)
CL_CGL_SHAREGROUP_KHR 0, CGL share group handle CGL share group to associate the OpenCL context with (available if the cl_khr_gl_sharing extension is enabled)
CL_EGL_DISPLAY_KHR EGL_NO_DISPLAY, EGLDisplay handle CGL share group to associate the OpenCL context with (available if the cl_khr_gl_sharing extension is enabled)
CL_GLX_DISPLAY_KHR None, X handle X Display an OpenGL context was created with respect to (available if the cl_khr_gl_sharing extension is enabled)
CL_WGL_HDC_KHR 0, HDC handle HDC an OpenGL context was created with respect to (available if the cl_khr_gl_sharing extension is enabled)
CL_CONTEXT_D3D11_DEVICE_KHR ID3D11Device * Specifies the ID3D11Device * to use for Direct3D 11 interoperability. The default value is NULL * (applies if the cl_khr_d3d11_sharing extension is supported)
device_type

A bit-field that identifies the type of device and is described in the table below.

cl_device_type Description
CL_DEVICE_TYPE_CPU An OpenCL device that is the host processor. The host processor runs the OpenCL implementations and is a single or multi-core CPU.
CL_DEVICE_TYPE_GPU An OpenCL device that is a GPU. By this we mean that the device can also be used to accelerate a 3D API such as OpenGL or DirectX.
CL_DEVICE_TYPE_ACCELERATOR Dedicated OpenCL accelerators (for example the IBM CELL Blade). These devices communicate with the host processor using a peripheral interconnect such as PCIe.
CL_DEVICE_TYPE_CUSTOM Dedicated accelerators that do not support programs written in OpenCL C.
CL_DEVICE_TYPE_DEFAULT The default OpenCL device in the system. The default device cannot be a CL_DEVICE_TYPE_CUSTOM device.
CL_DEVICE_TYPE_ALL All OpenCL devices available in the system except CL_DEVICE_TYPE_CUSTOM devices.
pfn_notify

A callback function that can be registered by the application. This callback function will be used by the OpenCL implementation to report information on errors that occur in this context. This callback function may be called asynchronously by the OpenCL implementation. It is the application's responsibility to ensure that the callback function is thread-safe. If pfn_notify is NULL, no callback function is registered. The parameters to this callback function are:

errinfo is a pointer to an error string.

private_info and cb represent a pointer to binary data that is returned by the OpenCL implementation that can be used to log additional information helpful in debugging the error.

user_data is a pointer to user supplied data.

There are a number of cases where error notifications need to be delivered due to an error that occurs outside a context. Such notifications may not be delivered through the pfn_notify callback. Where these notifications go is implementation-defined.

user_data

Passed as the user_data argument when pfn_notify is called. user_data can be NULL.

errcode_ret

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

Description

Only devices that are returned by clGetDeviceIDs for device_type are used to create the context. The context does not reference any sub-devices that may have been created from these devices.

Notes

clCreateContextFromType may return all or a subset of the actual physical devices present in the platform and that match device_type.

clCreateContextFromType and clCreateContext perform an implicit retain. This is very helpful for 3rd party libraries, which typically get a context passed to them by the application. However, it is possible that the application may delete the context without informing the library. Allowing functions to attach to (i.e. retain) and release a context solves the problem of a context being used by a library no longer being valid.

Errors

clCreateContextFromType returns a valid non-zero context and errcode_ret is set to CL_SUCCESS if the context is created successfully. Otherwise, it returns a NULL value with the following error vlaues returned in errcode_ret:

  • CL_INVALID_PLATFORM if properties is NULL and no platform could be selected or if platform value specified in properties is not a valid platform. If the cl_khr_gl_sharing extension is supported, this error is replaced (or not) by CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR and possibly CL_INVALID_OPERATION (see below and section 9.6.4 of the spec for clarification).
  • CL_INVALID_PROPERTY if context property name in properties is not a supported property name, or if the value specified for a supported property name is not valid, or if the same property name is specified more than once.
  • CL_INVALID_VALUE if pfn_notify is NULL but user_data is not NULL.
  • CL_INVALID_DEVICE_TYPE if device_type is not a valid value.
  • CL_DEVICE_NOT_AVAILABLE if no devices that match device_type and property values specified in properties are currently available.
  • CL_DEVICE_NOT_FOUND if no devices that match device_type and property values specified in properties were found.
  • 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_D3D10_DEVICE_KHR if the Direct3D 10 device specified for interoperability is not compatible with the devices against which the context is to be created (if the cl_khr_d3d10_sharing extension is enabled).
  • CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR when an invalid OpenGL context or share group object handle is specified in properties if the cl_khr_gl_sharing extension is enabled.
  • CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR: If no OpenGL or OpenGL ES context or share group is specified in the attribute list, then memory objects may not be shared, and calling any of the commands in section 9.7 will result in this error (if the cl_khr_gl_sharing extension is enabled).
  • CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR if the cl_khr_gl_sharing extension is enabled and if a context was specified by any of the following means:

    • Context specified for an EGL-based OpenGL ES or OpenGL implementation by setting the attributes CL_GL_CONTEXT_KHR and CL_EGL_DISPLAY_KHR.
    • Context was specified for a GLX-based OpenGL implementation by setting the attributes CL_GL_CONTEXT_KHR and CL_GLX_DISPLAY_KHR.
    • Context was specified for a WGL-based OpenGL implementation by setting the attributes CL_GL_CONTEXT_KHR and CL_WGL_HDC_KHR.
    and any of the following conditions hold:
    • The specified display and context attributes do not identify a valid OpenGL or OpenGL ES context.
    • The specified context does not support buffer and renderbuffer objects.
    • The specified context is not compatible with the OpenCL context being created (for example, it exists in a physically distinct address space, such as another hardware device, or does not support sharing data with OpenCL due to implementation restrictions).
  • CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR if a share group was specified for a CGL-based OpenGL implementation by setting the attribute CL_CGL_SHAREGROUP_KHR, and the specified share group does not identify a valid CGL share group object (only if the cl_khr_gl_sharing extension is enabled).
  • CL_INVALID_DX9_MEDIA_ADAPTER_KHR if the media adapter specified for interoperability is not compatible with the devices against which the context is to be created (only if the cl_khr_dx9_media_sharing extension is supported).
  • CL_INVALID_ADAPTER_KHR if any of the values of the properties CL_CONTEXT_ADAPTER_D3D9_KHR, CL_CONTEXT_ADAPTER_D3D9EX_KHR or CL_CONTEXT_ADAPTER_DXVA_KHR is non-NULL and does not specify a valid media adapter with which the cl_device_ids against which this context is to be created may interoperate. (only if the cl_khr_dx9_media_sharing extension is supported).
  • CL_INVALID_OPERATION if interoperability is specified by setting CL_CONTEXT_ADAPTER_D3D9_KHR, CL_CONTEXT_ADAPTER_D3D9EX_KHR or CL_CONTEXT_ADAPTER_DXVA_KHR to a non-NULL value, and interoperability with another graphics API is also specified. (only if the cl_khr_dx9_media_sharing extension is supported).
  • CL_INVALID_D3D11_DEVICE_KHR if the Direct3D 11 device specified for interoperability is not compatible with the devices against which the context is to be created (only if the cl_khr_d3d11_sharing extension is supported).
  • CL_INVALID_OPERATION if Direct3D 11 interoperability is specified by setting CL_INVALID_D3D11_DEVICE_KHR to a non-NULL value, and interoperability with another graphics API is also specified. (only if the cl_khr_d3d11_sharing extension is supported).
  • CL_INVALID_D3D11_DEVICE_KHR if the value of the property CL_CONTEXT_D3D11_DEVICE_KHR is non-NULL and does not specify a valid Direct3D 11 device with which the cl_device_ids against which this context is to be created may interoperate. (only if the cl_khr_d3d11_sharing extension is supported).

Specification

OpenCL Specification

Also see

clCreateContext, clGetContextInfo, clReleaseContext, clRetainContext, clGetContextInfo, Cardinality Diagram

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