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WIP: Add the VK_EXT_external_semaphore_drm_syncobj extension
This extension enables interop between timeline semaphores and Linux DRM synchronization objects (syncobj).
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‎appendices/VK_EXT_external_semaphore_drm_syncobj.adoc‎

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// Copyright 2026 The Khronos Group Inc.
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//
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// SPDX-License-Identifier: CC-BY-4.0
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include::{generated}/meta/{refprefix}VK_EXT_external_semaphore_drm_syncobj.adoc[]
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=== Other Extension Metadata
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*Last Modified Date*::
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2026-03-02
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*IP Status*::
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No known IP claims.
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*Contributors*::
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- Julian Orth
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- James Jones, NVIDIA
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=== Description
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This extension adds the ability to import and export timeline semaphores as DRM
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synchronization objects (syncobj).
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include::{generated}/interfaces/VK_EXT_external_semaphore_drm_syncobj.adoc[]
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=== Version History
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* Revision 1, 2026-03-02 (Julian Orth)
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** Initial revision

‎chapters/capabilities.adoc‎

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@@ -1618,6 +1618,12 @@ ifdef::VK_NV_external_sci_sync[]
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hardware engines including the CPU and software (intra-process and
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inter-process) operating domains and perform signal and wait operations.
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endif::VK_NV_external_sci_sync[]
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ifdef::VK_EXT_external_semaphore_drm_syncobj[]
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* ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT specifies a
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file descriptor handle to a Linux DRM synchronization object (syncobj).
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This type can only be used with timeline semaphores and Vulkan timeline
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semaphore values correspond to syncobj points.
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endif::VK_EXT_external_semaphore_drm_syncobj[]
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[NOTE]
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====
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ifdef::VK_NV_external_sci_sync[]
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| ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_SCI_SYNC_OBJ_BIT_NV | No restriction | No restriction
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endif::VK_NV_external_sci_sync[]
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ifdef::VK_EXT_external_semaphore_drm_syncobj[]
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| ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT | No restriction | No restriction
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endif::VK_EXT_external_semaphore_drm_syncobj[]
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|====
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--
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‎chapters/features.adoc‎

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@@ -9510,6 +9510,31 @@ include::{generated}/validity/structs/VkPhysicalDeviceShaderMixedFloatDotProduct
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--
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endif::VK_VALVE_shader_mixed_float_dot_product[]
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ifdef::VK_EXT_external_semaphore_drm_syncobj[]
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[open,refpage='VkPhysicalDeviceExternalSemaphoreDrmSyncobjFeaturesEXT',desc='Structure describing the external semaphore DRM syncobj features supported by the implementation',type='structs']
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--
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The sname:VkPhysicalDeviceExternalSemaphoreDrmSyncobjFeaturesEXT structure is defined
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as:
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include::{generated}/api/structs/VkPhysicalDeviceExternalSemaphoreDrmSyncobjFeaturesEXT.adoc[]
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This structure describes the following feature:
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* pname:sType is a elink:VkStructureType value identifying this structure.
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* pname:pNext is `NULL` or a pointer to a structure extending this
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structure.
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* [[features-externalSemaphoreDrmSyncobj]] pname:externalSemaphoreDrmSyncobj
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indicates whether the implementation has support for the
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ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT external
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semaphore handle type.
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:refpage: VkPhysicalDeviceExternalSemaphoreDrmSyncobjFeaturesEXT
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include::{chapters}/features.adoc[tag=features]
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include::{generated}/validity/structs/VkPhysicalDeviceExternalSemaphoreDrmSyncobjFeaturesEXT.adoc[]
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--
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endif::VK_EXT_external_semaphore_drm_syncobj[]
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[[features-requirements]]
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== Feature Requirements

‎chapters/synchronization.adoc‎

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slink:VkPhysicalDeviceExternalSciSyncFeaturesNV::pname:sciSyncExport>>
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features must: be enabled
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endif::VK_NV_external_sci_sync[]
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ifdef::VK_EXT_external_semaphore_drm_syncobj[]
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* If pname:handleTypes includes
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ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT, the
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<<features-externalSemaphoreDrmSyncobj,
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slink:VkPhysicalDeviceExternalSemaphoreDrmSyncobjFeaturesEXT::pname:externalSemaphoreDrmSyncobj>>
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feature must: be enabled
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* If pname:handleTypes includes
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ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT, the
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slink:VkSemaphoreTypeCreateInfo::pname:semaphoreType field must: be
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ename:VK_SEMAPHORE_TYPE_TIMELINE
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endif::VK_EXT_external_semaphore_drm_syncobj[]
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****
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include::{generated}/validity/structs/VkExportSemaphoreCreateInfo.adoc[]
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| Handle Type | Transference | Permanence Supported
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| ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_OPAQUE_FD_BIT | Reference | Temporary,Permanent
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| ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_SYNC_FD_BIT | Copy | Temporary
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ifdef::VK_EXT_external_semaphore_drm_syncobj[]
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| ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT | Reference | Permanent
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endif::VK_EXT_external_semaphore_drm_syncobj[]
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|====
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.Valid Usage
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semaphore from which pname:fd was exported must: not be
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ename:VK_SEMAPHORE_TYPE_TIMELINE
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endif::VK_BASE_VERSION_1_2,VK_KHR_timeline_semaphore[]
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ifdef::VK_EXT_external_semaphore_drm_syncobj[]
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* If pname:handleType is
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ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT, the
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<<features-externalSemaphoreDrmSyncobj,
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slink:VkPhysicalDeviceExternalSemaphoreDrmSyncobjFeaturesEXT::pname:externalSemaphoreDrmSyncobj>>
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feature must: be enabled
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* If pname:handleType is
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ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT, the
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slink:VkSemaphoreTypeCreateInfo::pname:semaphoreType field must: be
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ename:VK_SEMAPHORE_TYPE_TIMELINE
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endif::VK_EXT_external_semaphore_drm_syncobj[]
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****
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If pname:handleType is ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_SYNC_FD_BIT,

‎xml/vk.xml‎

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<member limittype="max,pot"><type>VkDeviceSize</type> <name>tensorDescriptorAlignment</name></member>
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<member limittype="noauto"><type>size_t</type> <name>tensorCaptureReplayOpaqueDataSize</name></member>
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</type>
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<type category="struct" name="VkPhysicalDeviceExternalSemaphoreDrmSyncobjFeaturesEXT" structextends="VkPhysicalDeviceFeatures2,VkDeviceCreateInfo">
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<member values="VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_EXTERNAL_SEMAPHORE_DRM_SYNCOBJ_FEATURES_EXT"><type>VkStructureType</type> <name>sType</name></member>
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<member optional="true" noautovalidity="true"><type>void</type>* <name>pNext</name></member>
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<member><type>VkBool32</type> <name>externalSemaphoreDrmSyncobj</name></member>
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</type>
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</types>
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<enum value="&quot;VK_SEC_extension_675&quot;" name="VK_SEC_EXTENSION_675_EXTENSION_NAME"/>
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</require>
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</extension>
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<extension name="VK_EXT_extension_678" number="678" author="EXT" contact="Julian Orth @mahkoh" supported="disabled">
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<extension name="VK_EXT_external_semaphore_drm_syncobj" number="678" type="device" depends="VK_VERSION_1_2" author="EXT" contact="Julian Orth @mahkoh" supported="vulkan">
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<require>
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<enum value="0" name="VK_EXT_EXTENSION_678_SPEC_VERSION"/>
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<enum value="&quot;VK_EXT_extension_678&quot;" name="VK_EXT_EXTENSION_678_EXTENSION_NAME"/>
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<enum value="1" name="VK_EXT_EXTERNAL_SEMAPHORE_DRM_SYNCOBJ_SPEC_VERSION"/>
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<enum value="&quot;VK_EXT_external_semaphore_drm_syncobj&quot;" name="VK_EXT_EXTERNAL_SEMAPHORE_DRM_SYNCOBJ_EXTENSION_NAME"/>
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<enum offset="0" extends="VkStructureType" name="VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_EXTERNAL_SEMAPHORE_DRM_SYNCOBJ_FEATURES_EXT"/>
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<enum bitpos="8" extends="VkExternalSemaphoreHandleTypeFlagBits" name="VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT"/>
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<type name="VkPhysicalDeviceExternalSemaphoreDrmSyncobjFeaturesEXT"/>
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<feature name="externalSemaphoreDrmSyncobj" struct="VkPhysicalDeviceExternalSemaphoreDrmSyncobjFeaturesEXT"/>
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</require>
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</extension>
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</extensions>

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