287 lines
12 KiB
Plaintext
287 lines
12 KiB
Plaintext
// Copyright (c) 2015-2017 The Khronos Group Inc.
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// Copyright notice at https://www.khronos.org/registry/speccopyright.html
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[[initialization]]
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= Initialization
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Before using Vulkan, an application must: initialize it by loading the
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Vulkan commands, and creating a sname:VkInstance object.
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[[initialization-functionpointers]]
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== Command Function Pointers
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// refBegin vkGetInstanceProcAddr Return a function pointer for a command
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Vulkan commands are not necessarily exposed statically on a platform.
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Function pointers for all Vulkan commands can: be obtained with the command:
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include::../api/protos/vkGetInstanceProcAddr.txt[]
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* pname:instance is the instance that the function pointer will be
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compatible with, or `NULL` for commands not dependent on any instance.
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* pname:pName is the name of the command to obtain.
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fname:vkGetInstanceProcAddr itself is obtained in a platform- and loader-
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specific manner.
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Typically, the loader library will export this command as a function symbol,
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so applications can: link against the loader library, or load it dynamically
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and look up the symbol using platform-specific APIs.
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Loaders are encouraged to export function symbols for all other core Vulkan
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commands as well; if this is done, then applications that use only the core
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Vulkan commands have no need to use fname:vkGetInstanceProcAddr.
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The table below defines the various use cases for
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fname:vkGetInstanceProcAddr and expected return value ("fp" is function
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pointer) for each case.
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The returned function pointer is of type tlink:PFN_vkVoidFunction, and must
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be cast to the type of the command being queried.
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.vkGetInstanceProcAddr behavior
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[width="80%",options="header"]
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|====
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| pname:instance | pname:pName | return value
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| * | `NULL` | undefined
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| invalid instance | * | undefined
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| `NULL` | flink:vkEnumerateInstanceExtensionProperties | fp
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| `NULL` | flink:vkEnumerateInstanceLayerProperties | fp
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| `NULL` | flink:vkCreateInstance | fp
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| `NULL` | * (any pname:pName not covered above) | `NULL`
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| instance | core Vulkan command | fp^1^
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| instance | enabled instance extension commands for pname:instance | fp^1^
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| instance | available device extension^2^ commands for pname:instance | fp^1^
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| instance | * (any pname:pName not covered above) | `NULL`
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|====
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1::
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The returned function pointer must: only be called with a dispatchable
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object (the first parameter) that is pname:instance or a child of
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pname:instance.
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e.g. sname:VkInstance, sname:VkPhysicalDevice, sname:VkDevice,
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sname:VkQueue, or sname:VkCommandBuffer.
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2::
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An "`available extension`" is an extension function supported by any of
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the loader, driver or layer.
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include::../validity/protos/vkGetInstanceProcAddr.txt[]
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// refEnd vkGetInstanceProcAddr PFN_vkVoidFunction
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// refBegin vkGetDeviceProcAddr Return a function pointer for a command
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In order to support systems with multiple Vulkan implementations comprising
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heterogeneous collections of hardware and software, the function pointers
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returned by fname:vkGetInstanceProcAddr may: point to dispatch code, which
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calls a different real implementation for different sname:VkDevice objects
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(and objects created from them).
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The overhead of this internal dispatch can: be avoided by obtaining
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device-specific function pointers for any commands that use a device or
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device-child object as their dispatchable object.
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Such function pointers can: be obtained with the command:
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include::../api/protos/vkGetDeviceProcAddr.txt[]
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The table below defines the various use cases for fname:vkGetDeviceProcAddr
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and expected return value for each case.
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The returned function pointer is of type tlink:PFN_vkVoidFunction, and must
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be cast to the type of the command being queried.
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.vkGetDeviceProcAddr behavior
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[width="80%",options="header"]
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|====
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| pname:device | pname:pName | return value
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| `NULL` | * | undefined
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| invalid device | * | undefined
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| device | `NULL` | undefined
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| device | core Vulkan command | fp^1^
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| device | enabled extension commands | fp^1^
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| device | * (any pname:pName not covered above) | `NULL`
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|====
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1::
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The returned function pointer must: only be called with a dispatchable
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object (the first parameter) that is pname:device or a child of
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pname:device.
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e.g. sname:VkDevice, sname:VkQueue, or sname:VkCommandBuffer.
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include::../validity/protos/vkGetDeviceProcAddr.txt[]
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// refEnd vkGetDeviceProcAddr PFN_vkVoidFunction
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// refBegin PFN_vkVoidFunction Dummy function pointer type returned by queries
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The definition of tlink:PFN_vkVoidFunction is:
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include::../api/funcpointers/PFN_vkVoidFunction.txt[]
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// refEnd PFN_vkVoidFunction vkGetDeviceProcAddr vkGetInstanceProcAddr
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ifdef::VK_KHR_get_physical_device_properties2[]
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=== Extending Physical Device From Device Extensions
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When the +VK_KHR_get_physical_device_properties2+ extension is enabled,
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physical device extension commands and structures can: be used with a
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physical device if the corresponding extension is enumerated by
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flink:vkEnumerateDeviceExtensionProperties for that physical device, even
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before a logical device has been created.
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To obtain a function pointer for a physical-device command from a device
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extension, an application can: use fname:vkGetInstanceProcAddr.
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This function pointer may: point to dispatch code, which calls a different
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real implementation for different sname:VkPhysicalDevice objects.
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Behavior is undefined if an extension physical-device command is called on a
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physical device that does not support the extension.
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Device extensions may: define structures that can: be added to the
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ptext:pNext chain of physical-device commands.
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Behavior is undefined if such an extension structure is passed to a physical
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device command for a physical device that does not support the extension.
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endif::VK_KHR_get_physical_device_properties2[]
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[[initialization-instances]]
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== Instances
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// refBegin VkInstance Opaque handle to a instance object
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There is no global state in Vulkan and all per-application state is stored
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in a sname:VkInstance object.
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Creating a sname:VkInstance object initializes the Vulkan library and allows
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the application to pass information about itself to the implementation.
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Instances are represented by sname:VkInstance handles:
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include::../api/handles/VkInstance.txt[]
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// refEnd VkInstance
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// refBegin vkCreateInstance Create a new Vulkan instance
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To create an instance object, call:
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include::../api/protos/vkCreateInstance.txt[]
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* pname:pCreateInfo points to an instance of slink:VkInstanceCreateInfo
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controlling creation of the instance.
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* pname:pAllocator controls host memory allocation as described in the
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<<memory-allocation, Memory Allocation>> chapter.
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* pname:pInstance points a sname:VkInstance handle in which the resulting
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instance is returned.
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fname:vkCreateInstance verifies that the requested layers exist.
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If not, fname:vkCreateInstance will return ename:VK_ERROR_LAYER_NOT_PRESENT.
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Next fname:vkCreateInstance verifies that the requested extensions are
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supported (e.g. in the implementation or in any enabled instance layer) and
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if any requested extension is not supported, fname:vkCreateInstance must:
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return ename:VK_ERROR_EXTENSION_NOT_PRESENT.
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After verifying and enabling the instance layers and extensions the
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sname:VkInstance object is created and returned to the application.
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If a requested extension is only supported by a layer, both the layer and
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the extension need to be specified at fname:vkCreateInstance time for the
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creation to succeed.
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.Valid Usage
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****
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* [[VUID-vkCreateInstance-ppEnabledExtensionNames-01388]]
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All <<extended-functionality-extensions-dependencies, required
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extensions>> for each extension in the
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slink:VkInstanceCreateInfo::pname:ppEnabledExtensionNames list must:
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also be present in that list.
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****
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include::../validity/protos/vkCreateInstance.txt[]
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// refBegin VkInstanceCreateInfo Structure specifying parameters of a newly created instance
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The sname:VkInstanceCreateInfo structure is defined as:
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include::../api/structs/VkInstanceCreateInfo.txt[]
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* pname:sType is the type of this structure.
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* pname:pNext is `NULL` or a pointer to an extension-specific structure.
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* pname:flags is reserved for future use.
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* pname:pApplicationInfo is `NULL` or a pointer to an instance of
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sname:VkApplicationInfo.
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If not `NULL`, this information helps implementations recognize behavior
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inherent to classes of applications.
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slink:VkApplicationInfo is defined in detail below.
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* pname:enabledLayerCount is the number of global layers to enable.
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* pname:ppEnabledLayerNames is a pointer to an array of
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pname:enabledLayerCount null-terminated UTF-8 strings containing the
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names of layers to enable for the created instance.
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See the <<extended-functionality-layers,Layers>> section for further
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details.
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* pname:enabledExtensionCount is the number of global extensions to
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enable.
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* pname:ppEnabledExtensionNames is a pointer to an array of
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pname:enabledExtensionCount null-terminated UTF-8 strings containing the
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names of extensions to enable.
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include::../validity/structs/VkInstanceCreateInfo.txt[]
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ifdef::VK_EXT_validation_flags[]
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include::VK_EXT_validation_flags.txt[]
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endif::VK_EXT_validation_flags[]
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// refBegin VkApplicationInfo Structure specifying application info
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The sname:VkApplicationInfo structure is defined as:
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include::../api/structs/VkApplicationInfo.txt[]
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* pname:sType is the type of this structure.
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* pname:pNext is `NULL` or a pointer to an extension-specific structure.
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* pname:pApplicationName is a pointer to a null-terminated UTF-8 string
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containing the name of the application.
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* pname:applicationVersion is an unsigned integer variable containing the
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developer-supplied version number of the application.
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* pname:pEngineName is a pointer to a null-terminated UTF-8 string
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containing the name of the engine (if any) used to create the
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application.
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* pname:engineVersion is an unsigned integer variable containing the
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developer-supplied version number of the engine used to create the
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application.
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* pname:apiVersion is the version of the Vulkan API against which the
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application expects to run, encoded as described in the
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<<fundamentals-versionnum,API Version Numbers and Semantics>> section.
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If pname:apiVersion is 0 the implementation must: ignore it, otherwise
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if the implementation does not support the requested pname:apiVersion,
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or an effective substitute for pname:apiVersion, it must: return
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ename:VK_ERROR_INCOMPATIBLE_DRIVER.
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The patch version number specified in pname:apiVersion is ignored when
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creating an instance object.
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Only the major and minor versions of the instance must: match those
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requested in pname:apiVersion.
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include::../validity/structs/VkApplicationInfo.txt[]
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// refBegin vkDestroyInstance Destroy an instance of Vulkan
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To destroy an instance, call:
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include::../api/protos/vkDestroyInstance.txt[]
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* pname:instance is the handle of the instance to destroy.
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* pname:pAllocator controls host memory allocation as described in the
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<<memory-allocation, Memory Allocation>> chapter.
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.Valid Usage
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****
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* [[VUID-vkDestroyInstance-instance-00629]]
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All child objects created using pname:instance must: have been destroyed
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prior to destroying pname:instance
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* [[VUID-vkDestroyInstance-instance-00630]]
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If sname:VkAllocationCallbacks were provided when pname:instance was
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created, a compatible set of callbacks must: be provided here
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* [[VUID-vkDestroyInstance-instance-00631]]
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If no sname:VkAllocationCallbacks were provided when pname:instance was
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created, pname:pAllocator must: be `NULL`
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****
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include::../validity/protos/vkDestroyInstance.txt[]
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