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Update the EGL_ANDROID_fence_sync spec.

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Change-Id: I26589e51c2023aed4da8a25a098b01804200ddc2
This commit is contained in:
Jamie Gennis 2012-07-20 11:55:07 -07:00
parent 4bb0164f8a
commit 648654d741
1 changed files with 105 additions and 50 deletions
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155
opengl/specs/EGL_ANDROID_fence_sync.txt
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@ -20,7 +20,7 @@ Status
Version
Version 1, May 29, 2012
Version 2, July 23, 2012
Number
@ -48,7 +48,9 @@ New Types
New Procedures and Functions
None.
EGLint eglDupAndroidFenceFDANDROID(
EGLDisplay dpy,
EGLSyncKHR);
New Tokens
@ -58,9 +60,14 @@ New Tokens
EGL_SYNC_ANDROID_FENCE_ANDROID 0x3144
Accepted by the <attribute> parameter of eglGetSyncAttribKHR:
Accepted by the <attrib_list> parameter of eglCreateSyncKHR:
EGL_SYNC_FENCE_FD_ANDROID 0x3145
EGL_SYNC_ANDROID_FENCE_FD_ANDROID 0x3145
Accepted by the <attrib_list> parameter of eglCreateSyncKHR, and returned
by eglDupAndroidFenceFDANDROID in the event of an error:
EGL_NO_ANDROID_FENCE_ANDROID -1
Returned in <value> when eglGetSyncAttribKHR is called with <attribute>
EGL_SYNC_CONDITION_KHR:
@ -73,43 +80,45 @@ Changes to Chapter 3 of the EGL 1.2 Specification (EGL Functions and Errors)
Objects), added by KHR_fence_sync
"If <type> is EGL_SYNC_ANDROID_FENCE_ANDROID, an EGL Android fence sync
object is created. In this case the EGL_SYNC_FENCE_FD_ANDROID attribute may
optionally be specified. If this attribute is specified, it must be set to
a file descriptor that refers to a native Android fence object.
object is created. In this case the EGL_SYNC_ANDROID_FENCE_FD_ANDROID
attribute may optionally be specified. If this attribute is specified, it
must be set to either a file descriptor that refers to a native Android
fence object or to the value EGL_NO_ANDROID_FENCE_ANDROID.
The default values for the EGL Android fence sync object attributes are as
follows:
Attribute Name Initial Attribute Value(s)
--------------- --------------------------
EGL_SYNC_TYPE_KHR EGL_SYNC_ANDROID_FENCE_ANDROID
EGL_SYNC_STATUS_KHR EGL_UNSIGNALED_KHR
EGL_SYNC_CONDITION_KHR EGL_SYNC_PRIOR_COMMANDS_COMPLETE_KHR
Attribute Name Initial Attribute Value(s)
--------------- --------------------------
EGL_SYNC_TYPE_KHR EGL_SYNC_ANDROID_FENCE_ANDROID
EGL_SYNC_STATUS_KHR EGL_UNSIGNALED_KHR
EGL_SYNC_CONDITION_KHR EGL_SYNC_PRIOR_COMMANDS_COMPLETE_KHR
EGL_SYNC_ANDROID_FENCE_FD_ANDROID EGL_NO_ANDROID_FENCE_ANDROID
Upon creation of an EGL Android fence sync object, the
EGL_SYNC_FENCE_FD_ANDROID attribute is set to a newly generated file
descriptor that refers to a native Android fence object. If the
EGL_SYNC_FENCE_FD_ANDROID attribute is specified in the eglCreateSyncKHR
call then the generated file descriptor refers to the same native Android
fence object as the file descriptor passed to eglCreateSyncKHR. Note,
however, that the value of the sync object attribute is *not* the same file
descriptor as the one passed to eglCreateSyncKHR - it simply refers to the
same underlying native Android fence object. Additionally, if the
EGL_SYNC_FENCE_FD_ANDROID attribute is specified then the
EGL_SYNC_CONDITION_KHR attribute is set to
EGL_SYNC_ANDROID_FENCE_SIGNALED_ANDROID and the EGL_SYNC_STATUS_KHR
If the EGL_SYNC_ANDROID_FENCE_FD_ANDROID attribute is not
EGL_NO_ANDROID_FENCE_ANDROID then the EGL_SYNC_CONDITION_KHR attribute is
set to EGL_SYNC_ANDROID_FENCE_SIGNALED_ANDROID and the EGL_SYNC_STATUS_KHR
attribute is set to reflect the signal status of the native Android fence
object."
object. Additionally, the EGL implementation assumes ownership of the file
descriptor, so the caller must not use it after calling eglCreateSyncKHR."
Modify Section 3.8.1 (Sync Objects), added by KHR_fence_sync, starting at
the seventh paragraph
"When a fence sync object is created or when an EGL Android fence sync
object is created without specifying the EGL_SYNC_FENCE_FD_ANDROID
attribute, eglCreateSyncKHR 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.
object is created with the EGL_SYNC_ANDROID_FENCE_FD_ANDROID attribute set
to EGL_NO_ANDROID_FENCE_ANDROID, eglCreateSyncKHR 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.
After associating the fence command with an EGL Android fence sync object,
the next Flush() operation performed by the current client API causes a
new native Android fence object to be created, and the
EGL_SYNC_ANDROID_FENCE_ANDROID attribute of the EGL Android fence object
is set to a file descriptor that refers to the new native Android fence
object. This new native Android fence object is signaled when the EGL
Android fence sync object is signaled.
When the condition of the sync object is satisfied by the fence command,
the sync is signaled by the associated client API context, causing any
@ -124,7 +133,8 @@ Changes to Chapter 3 of the EGL 1.2 Specification (EGL Functions and Errors)
state is affected by execution of the fence command.
The EGL_SYNC_ANDROID_FENCE_SIGNALED_ANDROID condition is satisfied by the
signaling of the native Android fence object. When this happens any
signaling of the native Android fence object referred to by the
EGL_SYNC_ANDROID_FENCE_FD_ANDROID attribute. When this happens any
eglClientWaitSyncKHR commands blocking on <sync> unblock."
Modify the list of eglCreateSyncKHR errors in Section 3.8.1 (Sync Objects),
@ -140,7 +150,7 @@ Changes to Chapter 3 of the EGL 1.2 Specification (EGL Functions and Errors)
empty (containing only EGL_NONE), EGL_NO_SYNC_KHR is returned and an
EGL_BAD_ATTRIBUTE error is generated.
* If <type> is EGL_SYNC_ANDROID_FENCE_ANDROID and <attrib_list> contains
an attribute other than EGL_SYNC_FENCE_FD_ANDROID, EGL_NO_SYNC_KHR is
an attribute other than EGL_SYNC_ANDROID_FENCE_FD_ANDROID, EGL_NO_SYNC_KHR is
returned and an EGL_BAD_ATTRIBUTE error is generated.
* If <type> is not a supported type of sync object,
EGL_NO_SYNC_KHR is returned and an EGL_BAD_ATTRIBUTE error is
@ -162,14 +172,12 @@ Changes to Chapter 3 of the EGL 1.2 Specification (EGL Functions and Errors)
Modify table 3.cc in Section 3.8.1 (Sync Objects), added by KHR_fence_sync
"
Attribute Description Supported Sync Objects
----------------- ----------------------- ----------------------
EGL_SYNC_TYPE_KHR Type of the sync object All
EGL_SYNC_STATUS_KHR Status of the sync object All
EGL_SYNC_CONDITION_KHR Signaling condition EGL_SYNC_FENCE_KHR and
EGL_SYNC_ANDROID_FENCE_ANDROID only
EGL_SYNC_FENCE_FD_ANDROID Native Android fence EGL_SYNC_ANDROID_FENCE_ANDROID only
object file descriptor
Attribute Description Supported Sync Objects
----------------- ----------------------- ----------------------
EGL_SYNC_TYPE_KHR Type of the sync object All
EGL_SYNC_STATUS_KHR Status of the sync object All
EGL_SYNC_CONDITION_KHR Signaling condition EGL_SYNC_FENCE_KHR and
EGL_SYNC_ANDROID_FENCE_ANDROID only
"
Modify the second paragraph description of eglDestroySyncKHR in Section
@ -177,9 +185,34 @@ Changes to Chapter 3 of the EGL 1.2 Specification (EGL Functions and Errors)
"If no errors are generated, EGL_TRUE is returned, and <sync> will no
longer be the handle of a valid sync object. Additionally, if <sync> is an
EGL Android fence sync object then the file descriptor stored in the
EGL_SYNC_FENCE_FD_ANDROID attribute is closed and is no longer a valid file
descriptor."
EGL Android fence sync object and the EGL_SYNC_ANDROID_FENCE_FD_ANDROID
attribute is not EGL_NO_ANDROID_FENCE_ANDROID then that file descriptor is
closed."
Add the following after the last paragraph of Section 3.8.1 (Sync
Objects), added by KHR_fence_sync
The command
EGLint eglDupAndroidFenceFDANDROID(
EGLdisplay dpy,
EGLSyncKHR sync);
duplicates the file descriptor stored in the
EGL_SYNC_ANDROID_FENCE_FD_ANDROID attribute of an EGL Android fence sync
object and returns the new file descriptor.
Errors
------
* If <sync> is not a valid sync object for <dpy>,
EGL_NO_ANDROID_FENCE_ANDROID is returned and an EGL_BAD_PARAMETER
error is generated.
* If the EGL_SYNC_ANDROID_FENCE_FD_ANDROID attribute of <sync> is
EGL_NO_ANDROID_FENCE_ANDROID, EGL_NO_ANDROID_FENCE_ANDROID is returned
and an EGL_BAD_PARAMETER error is generated.
* If <dpy> does not match the display passed to eglCreateSyncKHR
when <sync> was created, the behaviour is undefined."
Issues
@ -198,16 +231,38 @@ Issues
2. Who is responsible for dup'ing the Android fence file descriptors?
RESOLVED: The recipient of a file descriptor is responsible for dup'ing it
if it wishes to maintain a reference to the Android fence object.
RESOLVED: Whenever a file descriptor is passed into or returned from an
EGL call in this extension, ownership of that file descriptor is
transfered. The recipient of the file descriptor must close it when it is
no longer needed, and the provider of the file descriptor must dup it
before providing it if they require continued use of the native Android
fence.
This means that when eglCreateSyncKHR is called with an existing file
descriptor, the EGL implementation must dup it. On the other hand, when
eglGetSyncAttribKHR is called to query the file descriptor, it is the
responsibility of the caller to dup the file descriptor if it wishes to
maintain a reference that will outlast the EGLSyncKHR object.
3. Can the EGL_SYNC_ANDROID_FENCE_FD_ANDROID attribute be queried?
RESOLVED: No.
Returning the file descriptor owned by the EGL implementation would
violate the file descriptor ownership rule described in issue #2. Having
eglGetSyncAttribKHR return a different (dup'd) file descriptor each time
it's called seems wrong, so a new function was added to explicitly dup the
file descriptor.
That said, the attribute is useful both as a way to pass an existing file
descriptor to eglCreateSyncKHR and as a way to describe the subsequent
behavior of EGL Android fence sync objects, so it is left as an attribute
for which the value cannot be queried.
Revision History
#2 (Jamie Gennis, July 23, 2012)
- Changed the file descriptor ownership transferring behavior.
- Added the eglDupAndroidFenceFDANDROID function.
- Removed EGL_SYNC_ANDROID_FENCE_FD_ANDROID from the table of gettable
attributes.
- Added language specifying that a native Android fence is created at the
flush following the creation of an EGL Android fence sync object that is
not passed an existing native fence.
#1 (Jamie Gennis, May 29, 2012)
- Initial draft.