vkGetDeviceProcAddr(3)

# vkGetDeviceProcAddr(3) Manual Page

## Name

vkGetDeviceProcAddr - Return a function pointer for a command

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## 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 with the command:

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

## Parameters

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`.

## Description

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. Core commands beyond that version which are supported by the implementation may either return `NULL` or a function pointer, though the function pointer 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 2014-2022 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0