VK_KHR_maintenance6

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

1. 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 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.

2. Proposal

2.1. New features

The following features are exposed:

typedef struct VkPhysicalDeviceMaintenance6FeaturesKHR {
    VkStructureType    sType;
    void*              pNext;
    VkBool32           maintenance6;
} VkPhysicalDeviceMaintenance6FeaturesKHR;

  • The maintenance6 feature indicates support for the VK_KHR_maintenance6 extension.

2.2. New properties

The following device properties are exposed:

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.

2.3. New binding status structure

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.

2.4. 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.

2.5. New functions

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

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.

3. Issues

None.

4. Further Functionality

None.