WIP: Add the VK_EXT_external_semaphore_drm_syncobj extension

This extension enables interop between timeline semaphores and Linux DRM
synchronization objects (syncobj).

Author: mahkoh

appendices/VK_EXT_external_semaphore_drm_syncobj.adoc

@@ -0,0 +1,26 @@
+// Copyright 2026 The Khronos Group Inc.
+//
+// SPDX-License-Identifier: CC-BY-4.0
+
+include::{generated}/meta/{refprefix}VK_EXT_external_semaphore_drm_syncobj.adoc[]
+
+=== Other Extension Metadata
+
+*Last Modified Date*::
+    2026-03-02
+*IP Status*::
+    No known IP claims.
+*Contributors*::
+  - Julian Orth
+
+=== Description
+
+This extension adds the ability to import and export timeline semaphores as DRM
+synchronization objects (syncobj).
+
+include::{generated}/interfaces/VK_EXT_external_semaphore_drm_syncobj.adoc[]
+
+=== Version History
+
+  * Revision 1, 2026-03-02 (Julian Orth)
+  ** Initial revision

chapters/capabilities.adoc

@@ -1618,6 +1618,12 @@ ifdef::VK_NV_external_sci_sync[]
     hardware engines including the CPU and software (intra-process and
     inter-process) operating domains and perform signal and wait operations.
 endif::VK_NV_external_sci_sync[]
+ifdef::VK_EXT_external_semaphore_drm_syncobj[]
+  * ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT specifies a
+    file descriptor handle to a Linux DRM synchronization object (syncobj).
+    This type can only be used with timeline semaphores and Vulkan timeline
+    semaphore values correspond to syncobj points.
+endif::VK_EXT_external_semaphore_drm_syncobj[]
 
 [NOTE]
 ====
@@ -1651,6 +1657,9 @@ endif::VK_FUCHSIA_external_semaphore[]
 ifdef::VK_NV_external_sci_sync[]
 | ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_SCI_SYNC_OBJ_BIT_NV | No restriction | No restriction
 endif::VK_NV_external_sci_sync[]
+ifdef::VK_EXT_external_semaphore_drm_syncobj[]
+| ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT | No restriction | No restriction
+endif::VK_EXT_external_semaphore_drm_syncobj[]
 |====
 --
 

chapters/synchronization.adoc

@@ -3740,6 +3740,13 @@ ifdef::VK_NV_external_sci_sync[]
     slink:VkPhysicalDeviceExternalSciSyncFeaturesNV::pname:sciSyncExport>>
     features must: be enabled
 endif::VK_NV_external_sci_sync[]
+ifdef::VK_EXT_external_semaphore_drm_syncobj[]
+  * [[VUID-VkExportSemaphoreCreateInfo-handleTypes-100002]]
+    If pname:handleTypes includes
+    ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT, the
+    slink:VkSemaphoreTypeCreateInfo::pname:semaphoreType field must: be
+    ename:VK_SEMAPHORE_TYPE_TIMELINE
+endif::VK_EXT_external_semaphore_drm_syncobj[]
 ****
 
 include::{generated}/validity/structs/VkExportSemaphoreCreateInfo.adoc[]
@@ -5176,6 +5183,9 @@ The handle types supported by pname:handleType are:
 | Handle Type                                               | Transference | Permanence Supported
 | ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_OPAQUE_FD_BIT | Reference    | Temporary,Permanent
 | ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_SYNC_FD_BIT   | Copy         | Temporary
+ifdef::VK_EXT_external_semaphore_drm_syncobj[]
+| ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT | Reference | Permanent
+endif::VK_EXT_external_semaphore_drm_syncobj[]
 |====
 
 .Valid Usage
@@ -5209,6 +5219,13 @@ ifdef::VK_BASE_VERSION_1_2,VK_KHR_timeline_semaphore[]
     semaphore from which pname:fd was exported must: not be
     ename:VK_SEMAPHORE_TYPE_TIMELINE
 endif::VK_BASE_VERSION_1_2,VK_KHR_timeline_semaphore[]
+ifdef::VK_EXT_external_semaphore_drm_syncobj[]
+  * [[VUID-VkImportSemaphoreFdInfoKHR-handleType-100001]]
+    If pname:handleType is
+    ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT, the
+    slink:VkSemaphoreTypeCreateInfo::pname:semaphoreType field must: be
+    ename:VK_SEMAPHORE_TYPE_TIMELINE
+endif::VK_EXT_external_semaphore_drm_syncobj[]
 ****
 
 If pname:handleType is ename:VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_SYNC_FD_BIT,

xml/vk.xml

@@ -30347,6 +30347,13 @@ endif::VK_KHR_internally_synchronized_queues[]
                 <enum value="&quot;VK_SEC_extension_675&quot;"             name="VK_SEC_EXTENSION_675_EXTENSION_NAME"/>
             </require>
         </extension>
+        <extension name="VK_EXT_external_semaphore_drm_syncobj" number="100000" type="device" depends="VK_VERSION_1_2" author="EXT" contact="Julian Orth @mahkoh" supported="vulkan" nofeatures="true">
+            <require>
+                <enum value="1"                                                  name="VK_EXT_EXTERNAL_SEMAPHORE_DRM_SYNCOBJ_SPEC_VERSION"/>
+                <enum value="&quot;VK_EXT_external_semaphore_drm_syncobj&quot;"  name="VK_EXT_EXTERNAL_SEMAPHORE_DRM_SYNCOBJ_EXTENSION_NAME"/>
+                <enum bitpos="8" extends="VkExternalSemaphoreHandleTypeFlagBits" name="VK_EXTERNAL_SEMAPHORE_HANDLE_TYPE_DRM_SYNCOBJ_BIT_EXT"/>
+            </require>
+        </extension>
     </extensions>
     <formats>
         <format name="VK_FORMAT_R4G4_UNORM_PACK8" class="8-bit" blockSize="1" texelsPerBlock="1" packed="8">