C Specification

In order to support systems with multiple Vulkan implementations, the function pointers returned by vkGetInstanceProcAddr may point to dispatch code that calls a different real implementation for different VkDevice objects or their child objects. The overhead of the internal dispatch for VkDevice objects can be avoided by obtaining device-specific function pointers for any commands that use a device or device-child object as their dispatchable object. Such function pointers can be obtained by calling:

// Provided by VK_VERSION_1_0
PFN_vkVoidFunction vkGetDeviceProcAddr(
    VkDevice                                    device,
    const char*                                 pName);

Description

The table below defines the various use cases for vkGetDeviceProcAddr and expected return value (“fp” is “function pointer”) for each case. A valid returned function pointer (“fp”) must not be NULL.

The returned function pointer is of type PFN_vkVoidFunction, and must be cast to the type of the command being queried before use. The function pointer must only be called with a dispatchable object (the first parameter) that is device or a child of device.

Table 1. vkGetDeviceProcAddr behavior
device pName return value

NULL

*1

undefined

invalid device

*1

undefined

device

NULL

undefined

device

requested core version2 device-level dispatchable command3

fp4

device

enabled extension device-level dispatchable command3

fp4

any other case, not covered above

NULL
1

"*" means any representable value for the parameter (including valid values, invalid values, and NULL).

2

Device-level commands which are part of the core version specified by VkApplicationInfo::apiVersion when creating the instance will always return a valid function pointer. If the maintenance5 feature is enabled, core commands beyond that version which are supported by the implementation will return NULL, otherwise the implementation may either return NULL or a function pointer. If a function pointer is returned, it must not be called.

3

In this function, device-level excludes all physical-device-level commands.

4

The returned function pointer must only be called with a dispatchable object (the first parameter) that is device or a child of device e.g. VkDevice, VkQueue, or VkCommandBuffer.

Valid Usage (Implicit)

  • VUID-vkGetDeviceProcAddr-device-parameter
    device must be a valid VkDevice handle

  • VUID-vkGetDeviceProcAddr-pName-parameter
    pName must be a null-terminated UTF-8 string

See Also

PFN_vkVoidFunction, VK_VERSION_1_0, VkDevice

Document Notes

For more information, see the Vulkan Specification

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

Copyright

Copyright 2014-2024 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0