kc3-lang/angle/extensions/EGL_ANGLE_metal_shared_event_sync.txt

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• Hash : aa5b97de
  Author :
  Date : 2023-03-06T17:59:43
  

  ANGLE_metal_shared_event_sync: Control signaling external events
  
  It was assumed that the external MTLSharedEvent passed to eglCreateSync
  should be signaled by the GL. This change adds
  EGL_SYNC_METAL_SHARED_EVENT_SIGNALED_ANGLE, which when passed as the
  value for EGL_SYNC_CONDITION during eglCreateSync, changes the behavior
  to not insert a fence command into the command stream.
  
  Test: angle_end2end_tests --gtest_filter=EGLSyncTestMetalSharedEvent.AngleMetalSharedEventSync_WaitSync_ExternallySignaled
  Bug: angleproject:8064
  Change-Id: Ia1b8615b976f293d411b7d2be506b0ac87d64dee
  Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4307152
  Reviewed-by: Kenneth Russell <kbr@chromium.org>
  Commit-Queue: Kenneth Russell <kbr@chromium.org>
  Reviewed-by: Sunny Sachanandani <sunnyps@chromium.org>
  

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• extensions/EGL_ANGLE_metal_shared_event_sync.txt

• Name
  
      ANGLE_metal_shared_event_sync
  
  Name Strings
  
      EGL_ANGLE_metal_shared_event_sync
  
  Contributors
  
      Dan Glastonbury, Apple
  
  Contacts
  
      Dan Glastonbury, Apple (djg 'at' apple.com)
  
  Status
  
      Draft
  
  Version
  
      Version 2, 2022-09-08
  
  Number
  
      EGL Extensions XXX
  
  Extension Type
  
      EGL display extension
  
  Dependencies
  
      This extension is written against the wording of the EGL 1.5
      Specification.
  
  Overview
  
      This extension enables the creation of EGL fence sync objects that are
      associated with a native Metal event object.  The EGL fence sync objects
      have nearly identical semantics to those sync objects defined by the
      EGL 1.5 Specification, except that they have an additional attribute
      storing the id<MTLSharedEvent> referring to the metal event object and
      the integer value to signal the event with.
  
  New Types
  
      None.
  
  New Procedures and Functions
  
      void* eglCopyMetalSharedEventANGLE(
                          EGLDisplay dpy,
                          EGLSync sync);
  
  New Tokens
  
      Accepted by the <type> parameter of eglCreateSync, and returned
      in <value> when eglGetSyncAttrib is called with <attribute>
      EGL_SYNC_TYPE:
  
      EGL_SYNC_METAL_SHARED_EVENT_ANGLE                   0x34D8
  
      Accepted by the <attrib_list> parameter of eglCreateSync:
  
      EGL_SYNC_METAL_SHARED_EVENT_OBJECT_ANGLE            0x34D9
      EGL_SYNC_METAL_SHARED_EVENT_SIGNAL_VALUE_LO_ANGLE   0x34DA
      EGL_SYNC_METAL_SHARED_EVENT_SIGNAL_VALUE_HI_ANGLE   0x34DB
      EGL_SYNC_METAL_SHARED_EVENT_SIGNALED_ANGLE          0x34DC
  
  Additions to the EGL Specification
  
      Add the following after the first paragraph of Section 3.8.1.1 (Creating
      Fence Sync Objects),
  
      "If <type> is EGL_SYNC_METAL_SHARED_EVENT_ANGLE, an EGL metal event sync
      object is created. In this case the
      EGL_SYNC_METAL_SHARED_EVENT_OBJECT_ANGLE,
      EGL_SYNC_METAL_SHARED_EVENT_SIGNAL_VALUE_LO_ANGLE,
      EGL_SYNC_METAL_SHARED_EVENT_SIGNAL_VALUE_HI_ANGLE, and
      EGL_SYNC_CONDITION may be specified.
  
      If EGL_SYNC_METAL_SHARED_EVENT_OBJECT_ANGLE attribute is specified, it must
      be set to a pointer to a valid id<MTLSharedEvent>, or to a NULL pointer. If
      EGL_SYNC_METAL_SHARED_EVENT_OBJECT_ANGLE is not specified, or is a NULL
      pointer, the EGL implementation will create a Metal event
      object. Additionally, the EGL implementation assumes ownership of the Metal
      event object and will follow Objective-C behavior and increase the Metal
      event object's retain count.
  
      EGL_SYNC_METAL_SHARED_EVENT_SIGNAL_VALUE_LO_ANGLE and
      EGL_SYNC_METAL_SHARED_EVENT_HI_ANGLE are optional attributes specifying the
      low and high 32-bit parts of an unsigned 64-bit value to be set when the
      event is signaled. If these attributes are unspecified, the event is
      signaled with one more than the event's signaledValue property at the time
      of EGLSync creation. The signal value will wrap to 0 if the initial
      signaledValue is the maximum value for uint64_t.
  
      If EGL_SYNC_CONDITION attribute is specified, it must be either
      EGL_SYNC_PRIOR_COMMANDS_COMPLETE or EGL_SYNC_METAL_SHARED_EVENT_SIGNALED_ANGLE.
      The EGL_SYNC_METAL_SHARED_EVENT_SIGNALED_ANGLE condition is satisfied by the
      signaling of the MTLSharedEvent referred to by the
      EGL_SYNC_METAL_SHARED_EVENT_OBJECT_ANGLE attribute. When this happens any
      eglClientWaitSync commands blocking on <sync> unblock.
  
      The default values for the EGL metal event sync object attributes are as
      follows:
  
        Attribute Name                     Initial Attribute Value(s)
        --------------                     --------------------------
        EGL_SYNC_TYPE                      EGL_SYNC_METAL_SHARED_EVENT_ANGLE
        EGL_SYNC_STATUS                    EGL_UNSIGNALED
        EGL_SYNC_CONDITION                 EGL_SYNC_PRIOR_COMMANDS_COMPLETE
  
      Modify the list of eglCreateSync errors in Section 3.8.1.2 (Creating OpenCL
      Event Sync Objects)
  
      "Errors
       ------
      ..."
  
      Modify the second paragraph of Section 3.8.1.1 (Creating Fence Sync Objects),
  
      When a fence sync object is created or when an EGL metal shared event sync
      object is created with the EGL_SYNC_CONDITION attribute set to
      EGL_SYNC_PRIOR_COMMANDS_COMPLETE, eglCreateSync also inserts a fence command
      into the command stream of the bound client API’s current context (i.e., the
      context returned by eglGetCurrentContext), and associates it with the newly
      created sync object.
  
      Add the following after the last paragraph of Section 3.8.1 (Sync Objects):
  
      "The command
  
           void* eglCopyMetalSharedEventANGLE(
                                  EGLDisplay dpy,
                                  EGLSync sync);
  
      increases the retain count of the id<MTLSharedEvent> stored in the
      EGL_SYNC_METAL_SHARED_EVENT_OBJECT_ANGLE attribute of an EGL metal shared
      event sync object and returns a pointer to the event as a void* pointer. If
      this returns a non-null value, the caller is responsible for releasing the
      MTLSharedEvent once after calling this function."
  
  Issues
  
      1. What should the name be? METAL_EVENT_ANGLE? MTL or METAL?
  
  Revision History
  
      Version 1, 2022-05-17
        - Initial draft
      Version 2, 2022-09-08
        - Add eglCopyMetalSharedEventANGLE function
      Version 3, 2023-03-06
        - Add EGL_SYNC_METAL_SHARED_EVENT_SIGNALED_ANGLE
  
  

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