// Copyright 2023-2024 The Khronos Group Inc.
// SPDX-License-Identifier: CC-BY-4.0

= Proposal Template
:toc: left
:refpage: https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/
:sectnums:

This proposal details and addresses the issues solved by the `VK_KHR_maintenance6` extension.

== Problem Statement

Over time, a collection of minor features, none of which would warrant an
entire extension of their own, requires the creation of a maintenance
extension.

The following is a list of issues considered in this proposal:

  * `vkBindBufferMemory2` and `vkBindImageMemory2` accept arrays of memory
    binding parameters, but the commands only return a single `VkResult` value.
    This makes it impossible to identify which specific memory binding operation
    failed, and leaves resources in an indeterminate, unusable state.
  * Add a property to describe if an implementation clamps the inputs to
    fragment shading rate combiner operations.
  * There are some use cases where an index buffer must be bound, even if it is
    not used, and the specification currently forbids the use of
    `VK_NULL_HANDLE`.
  * Need a `maxCombinedImageSamplerDescriptorCount` value, for cases where
    you need to create a descriptor set layout, but do not know which
    formats will be used (and therefore cannot query it).
  * Creating image views with ename:VK_IMAGE_CREATE_BLOCK_TEXEL_VIEW_COMPATIBLE_BIT
    and multiple layers is supported by all modern hardware, so this should be exposed
    by the API.
  * `pNext` extensible *2 versions of all descriptor binding commands.

== Proposal

=== New features

The following features are exposed:

[source,c]
----
typedef struct VkPhysicalDeviceMaintenance6FeaturesKHR {
    VkStructureType    sType;
    void*              pNext;
    VkBool32           maintenance6;
} VkPhysicalDeviceMaintenance6FeaturesKHR;
----

  * The `maintenance6` feature indicates support for the `VK_KHR_maintenance6` extension.

=== New properties

The following device properties are exposed:

[source,c]
----
typedef struct VkPhysicalDeviceMaintenance6PropertiesKHR {
    VkStructureType    sType;
    void*              pNext;
    VkBool32           blockTexelViewCompatibleMultipleLayers;
    uint32_t           maxCombinedImageSamplerDescriptorCount;
    VkBool32           fragmentShadingRateClampCombinerInputs;
} VkPhysicalDeviceMaintenance6PropertiesKHR;
----

  * The `blockTexelViewCompatibleMultipleLayers` property indicates whether a `VK_IMAGE_CREATE_BLOCK_TEXEL_VIEW_COMPATIBLE_BIT`
  can be used with a `layerCount` of greater than `1`.
  * The `maxCombinedImageSamplerDescriptorCount` property indicates the maximum number of descriptors needed for any of the multi-planar formats
  supported by the implementation that require `YCbCr` conversion .
  * The `fragmentShadingRateClampCombinerInputs` property indicates if an implementation clamps the inputs to fragment shading rate combiner operations.

=== New binding status structure

[source,c]
----
typedef struct VkBindMemoryStatusKHR {
    VkStructureType    sType;
    const void*        pNext;
    VkResult*          pResult;
} VkBindMemoryStatusKHR;
----

The `VkBindMemoryStatusKHR` structure can be included in the `pNext` chain of `VkBindBufferMemoryInfo` and
`VkBindImageMemoryInfo`, allowing applications to retrieve `VkResult` values for individual memory binding operations.

=== New index buffer binding functionality

`VK_NULL_HANDLE` can now be used in index buffer binding functions, in place
of a valid `VkBuffer` handle. When the `nullDescriptor` feature is enabled,
every index fetched results in a value of zero.


=== New functions

The following new functions are added in order to support future extensibility:

[source,c]
----
typedef struct VkBindDescriptorSetsInfoKHR {
    VkStructureType               sType;
    const void*                   pNext;
    VkShaderStageFlags            stageFlags;
    VkPipelineLayout              layout;
    uint32_t                      firstSet;
    uint32_t                      descriptorSetCount;
    const VkDescriptorSet*        pDescriptorSets;
    uint32_t                      dynamicOffsetCount;
    const uint32_t*               pDynamicOffsets;
} VkBindDescriptorSetsInfoKHR;

typedef struct VkPushConstantsInfoKHR {
    VkStructureType               sType;
    const void*                   pNext;
    VkPipelineLayout              layout;
    VkShaderStageFlags            stageFlags;
    uint32_t                      offset;
    uint32_t                      size;
    const void*                   pValues;
} VkPushConstantsInfoKHR;

typedef struct VkPushDescriptorSetInfoKHR {
    VkStructureType               sType;
    const void*                   pNext;
    VkShaderStageFlags            stageFlags;
    VkPipelineLayout              layout;
    uint32_t                      set;
    uint32_t                      descriptorWriteCount;
    const VkWriteDescriptorSet*   pDescriptorWrites;
} VkPushDescriptorSetInfoKHR;

typedef struct VkPushDescriptorSetWithTemplateInfoKHR {
    VkStructureType               sType;
    const void*                   pNext;
    VkDescriptorUpdateTemplate    descriptorUpdateTemplate;
    VkPipelineLayout              layout;
    uint32_t                      set;
    const void*                   pData;
} VkPushDescriptorSetWithTemplateInfoKHR;

typedef struct VkSetDescriptorBufferOffsetsInfoEXT {
    VkStructureType               sType;
    const void*                   pNext;
    VkShaderStageFlags            stageFlags;
    VkPipelineLayout              layout;
    uint32_t                      firstSet;
    uint32_t                      setCount;
    const uint32_t*               pBufferIndices;
    const VkDeviceSize*           pOffsets;
} VkSetDescriptorBufferOffsetsInfoEXT;

typedef struct VkBindDescriptorBufferEmbeddedSamplersInfoEXT {
    VkStructureType       sType;
    const void*           pNext;
    VkShaderStageFlags    stageFlags;
    VkPipelineLayout      layout;
    uint32_t              set;
} VkBindDescriptorBufferEmbeddedSamplersInfoEXT;

void vkCmdBindDescriptorSets2KHR(
  VkCommandBuffer                                       commandBuffer,
  const VkBindDescriptorSetsInfoKHR*                    pBindDescriptorSetsInfo);

void vkCmdPushConstants2KHR(
  VkCommandBuffer                                       commandBuffer,
  const VkPushConstantsInfoKHR*                         pPushConstantsInfo);

void vkCmdPushDescriptorSet2KHR(
  VkCommandBuffer                                       commandBuffer,
  const VkPushDescriptorSetInfoKHR*                     pPushDescriptorSetInfo);

void vkCmdPushDescriptorSetWithTemplate2KHR(
  VkCommandBuffer                                       commandBuffer,
  const VkPushDescriptorSetWithTemplateInfoKHR*         pPushDescriptorSetWithTemplateInfo);

void vkCmdSetDescriptorBufferOffsets2EXT(
  VkCommandBuffer                                       commandBuffer,
  const VkSetDescriptorBufferOffsetsInfoEXT*            pSetDescriptorBufferOffsetsInfo);

void vkCmdBindDescriptorBufferEmbeddedSamplers2EXT(
  VkCommandBuffer                                       commandBuffer,
  const VkBindDescriptorBufferEmbeddedSamplersInfoEXT*  pBindDescriptorBufferEmbeddedSamplersInfo);
----

The parameters of the structures are identical to the arguments of the
existing functions, except that `VkPipelineBindPoint` is replaced with
`VkShaderStageFlagBits`.

== Issues

None.


== Further Functionality

None.