[PATCH wayland-protocols v5] Add zwp_linux_explicit_synchronization_v1
Pekka Paalanen
ppaalanen at gmail.com
Wed Nov 7 10:19:31 UTC 2018
On Tue, 6 Nov 2018 14:58:14 +0200
Alexandros Frantzis <alexandros.frantzis at collabora.com> wrote:
> Signed-off-by: Alexandros Frantzis <alexandros.frantzis at collabora.com>
> ---
>
> Changes in patch v5:
> - Further clarified the per-commit nature of buffer_release.
> - Used the wp_linux_dmabuf name to refer to all versions of that protocol.
> - Fixed wl_buffer.attach typo.
> - Clarified when an INVALID_FENCE error is raised.
> - Improved wording explaining the double-buffer state of buffer_release.
> - Allowed get_release requests on all non-null buffers.
> - Clarified that the compositor is free to select buffer_release events
> on a release by release basis.
> - Changed buffer_release to be self-destroyed after it emits an event.
>
> Changes in patch v4:
> - Guaranteed protocol compatibility only with zwp_linux_dmabuf buffers.
> - Added the UNSUPPORTED_BUFFER error.
>
> Changes in patch v3:
> - Reworded implicit/explicit synchronization intro in
> zwp_surface_synchronization_v1 description.
> - Removed confusing mention of wl_buffer.release in
> zwp_surface_synchronization_v1 description.
> - Clarified which fences are affected on sync object destruction.
> - Removed unclear mention about wl_buffer destruction
> in fenced_release description.
> - Clarified that the release events and their guarantees apply to
> the relevant commit only.
> - Reformatted text.
>
> Changes in patch v2:
> - Added NO_SURFACE error for zwp_surface_synchronization_v1 requests.
> - Removed restriction to destroy a zwp_surface_synchronization_v1 object
> after the associated wl_surface is destroyed.
> - Clarified which buffer the acquire fence is associated with.
> - Clarified that exactly one event, either a fenced_release or a
> immediate_release, will be emitted for each commit.
>
> Makefile.am | 1 +
> .../linux-explicit-synchronization/README | 6 +
> ...x-explicit-synchronization-unstable-v1.xml | 226 ++++++++++++++++++
> 3 files changed, 233 insertions(+)
> create mode 100644 unstable/linux-explicit-synchronization/README
> create mode 100644 unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml
Hi alf,
only nitpicks below.
>
> diff --git a/Makefile.am b/Makefile.am
> index 6394e26..7dfbb9e 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -21,6 +21,7 @@ unstable_protocols = \
> unstable/xdg-output/xdg-output-unstable-v1.xml \
> unstable/input-timestamps/input-timestamps-unstable-v1.xml \
> unstable/xdg-decoration/xdg-decoration-unstable-v1.xml \
> + unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml \
> $(NULL)
>
> stable_protocols = \
> diff --git a/unstable/linux-explicit-synchronization/README b/unstable/linux-explicit-synchronization/README
> new file mode 100644
> index 0000000..f13b404
> --- /dev/null
> +++ b/unstable/linux-explicit-synchronization/README
> @@ -0,0 +1,6 @@
> +Linux explicit synchronization (dma-fence) protocol
> +
> +Maintainers:
> +David Reveman <reveman at chromium.org>
> +Daniel Stone <daniels at collabora.com>
> +Alexandros Frantzis <alexandros.frantzis at collabora.com>
> diff --git a/unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml b/unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml
> new file mode 100644
> index 0000000..834f2e0
> --- /dev/null
> +++ b/unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml
> @@ -0,0 +1,226 @@
> +<?xml version="1.0" encoding="UTF-8"?>
> +<protocol name="zwp_linux_explicit_synchronization_unstable_v1">
> +
> + <copyright>
> + Copyright 2016 The Chromium Authors.
> + Copyright 2017 Intel Corporation
> + Copyright 2018 Collabora, Ltd
> +
> + Permission is hereby granted, free of charge, to any person obtaining a
> + copy of this software and associated documentation files (the "Software"),
> + to deal in the Software without restriction, including without limitation
> + the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + and/or sell copies of the Software, and to permit persons to whom the
> + Software is furnished to do so, subject to the following conditions:
> +
> + The above copyright notice and this permission notice (including the next
> + paragraph) shall be included in all copies or substantial portions of the
> + Software.
> +
> + THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> + DEALINGS IN THE SOFTWARE.
> + </copyright>
> +
> + <interface name="zwp_linux_explicit_synchronization_v1" version="1">
> + <description summary="protocol for providing explicit synchronization">
> + This global is a factory interface, allowing clients to request
> + explicit synchronization for buffers on a per-surface basis.
> +
> + See zwp_surface_synchronization_v1 for more information.
> +
> + This interface is derived from Chromium's
> + zcr_linux_explicit_synchronization_v1.
> +
> + Warning! The protocol described in this file is experimental and
> + backward incompatible changes may be made. Backward compatible changes
> + may be added together with the corresponding interface version bump.
> + Backward incompatible changes are done by bumping the version number in
> + the protocol and interface names and resetting the interface version.
> + Once the protocol is to be declared stable, the 'z' prefix and the
> + version number in the protocol and interface names are removed and the
> + interface version number is reset.
> + </description>
> +
> + <request name="destroy" type="destructor">
> + <description summary="destroy explicit synchronization factory object">
> + Destroy this explicit synchronization factory object. Other objects,
> + including zwp_surface_synchronization_v1 objects created by this
> + factory, shall not be affected by this request.
> + </description>
> + </request>
> +
> + <enum name="error">
> + <entry name="synchronization_exists" value="0"
> + summary="the surface already has a synchronization object associated"/>
> + </enum>
> +
> + <request name="get_synchronization">
> + <description summary="extend surface interface for explicit synchronization">
> + Instantiate an interface extension for the given wl_surface to provide
> + explicit synchronization.
> +
> + If the given wl_surface already has an explicit synchronization object
> + associated, the synchronization_exists protocol error is raised.
> + </description>
> +
> + <arg name="id" type="new_id" interface="zwp_surface_synchronization_v1"
> + summary="the new synchronization interface id"/>
> + <arg name="surface" type="object" interface="wl_surface"
> + summary="the surface"/>
> + </request>
> + </interface>
> +
> + <interface name="zwp_surface_synchronization_v1" version="1">
> + <description summary="per-surface explicit synchronization support">
> + This object implements per-surface explicit synchronization.
> +
> + Synchronization refers to co-ordination of pipelined operations performed
> + on buffers. Most GPU clients will schedule an asynchronous operation to
> + render to the buffer, then immediately send the buffer to the compositor
> + to be attached to a surface.
> +
> + In implicit synchronization, ensuring that the rendering operation is
> + complete before the compositor displays the buffer is an implementation
> + detail handled by either the kernel or userspace graphics driver.
> +
> + By contrast, in explicit synchronization, dma_fence objects mark when the
> + asynchronous operations are complete. When submitting a buffer, the
> + client provides an acquire fence which will be waited on before the
> + compositor accesses the buffer. The Wayland server, through a
> + zwp_buffer_release_v1 object, will inform the client with an event which
> + may be accompanied by a release fence, when the compositor will no longer
> + access the buffer contents due to the specific commit that requested the
> + release event.
> +
> + Each surface can be associated with only one object of this interface at
> + any time.
> +
> + Explicit synchronization is guaranteed to be supported only for buffers
> + created with any version of the wp_linux_dmabuf buffer factory.
> + </description>
> +
> + <request name="destroy" type="destructor">
> + <description summary="destroy synchronization object">
> + Destroy this explicit synchronization object.
> +
> + Any fence set by this object with set_acquire_fence since the last
> + commit will be discarded by the server. Any fences set by this object
> + before the last commit are not affected.
> +
> + zwp_buffer_release_v1 objects created by this object are not affected
> + by this request.
> + </description>
> + </request>
> +
> + <enum name="error">
> + <entry name="invalid_fence" value="0"
> + summary="the fence specified by the client could not be imported"/>
> + <entry name="duplicate_fence" value="1"
> + summary="multiple fences added for a single surface commit"/>
> + <entry name="duplicate_release" value="2"
> + summary="multiple releases added for a single surface commit"/>
> + <entry name="no_surface" value="3"
> + summary="the associated wl_surface was destroyed"/>
> + <entry name="unsupported_buffer" value="4"
> + summary="the buffer does not support explicit synchronization"/>
> + </enum>
> +
> + <request name="set_acquire_fence">
> + <description summary="set the acquire fence">
> + Set the acquire fence that must be signaled before the compositor
> + may sample from the buffer attached with wl_buffer.attach. The fence
Still a wl_buffer.attach here, should be wl_surface.attach.
> + is a dma_fence kernel object.
> +
> + The acquire fence is double-buffered state, and will be applied on the
> + next wl_surface.commit request for the associated surface. Thus, it
> + applies only to the buffer that is attached to the surface at commit
> + time.
> +
> + If the provided fd is not a valid dma_fence fd, then an INVALID_FENCE
> + error is raised.
> +
> + If a fence has already been attached during the same commit cycle, a
> + DUPLICATE_FENCE error is raised.
> +
> + If the associated wl_surface was destroyed, a NO_SURFACE error is
> + raised.
> +
> + If at surface commit time the attached buffer does not support explicit
> + synchronization, or there is no buffer attached, an UNSUPPORTED_BUFFER
> + error is raised.
> + </description>
> + <arg name="fd" type="fd" summary="acquire fence fd"/>
> + </request>
> +
> + <request name="get_release">
> + <description summary="release fence for last-attached buffer">
> + Create a listener for the release of the buffer attached by the
> + client with wl_buffer.attach. See zwp_buffer_release_v1
wl_surface.attach
> + documentation for more information.
> +
> + The release object is double-buffered state, and will be associated
> + with the buffer that is attached to the surface at wl_surface.commit
> + time.
> +
> + If a zwp_buffer_release_v1 object has already been requested for
> + the surface in the same commit cycle, a DUPLICATE_RELEASE error
> + is signaled to the client.
"is raised"
> +
> + If the associated wl_surface was destroyed, a NO_SURFACE error
> + is signaled to the client.
"is raised", just to use the language consistently.
> +
> + If at surface commit time there is no buffer attached, an
> + UNSUPPORTED_BUFFER error is raised.
This reads a little odd, do we need another error code for "no buffer"?
> + </description>
> + <arg name="release" type="new_id" interface="zwp_buffer_release_v1"
> + summary="new zwp_buffer_release_v1 object"/>
> + </request>
> + </interface>
> +
> + <interface name="zwp_buffer_release_v1" version="1">
> + <description summary="buffer release explicit synchronization">
> + This object is instantiated in response to a
> + zwp_surface_synchronization_v1.get_release request.
> +
> + It provides an alternative to wl_buffer.release events, providing a
> + unique release from a single wl_surface.commit request. The release event
> + also supports explicit synchronization, providing a fence FD for the
> + client to synchronize against.
> +
> + Exactly one event, either a fenced_release or an immediate_release, will
> + be emitted for the wl_surface.commit request. The compositor can choose
> + release by release which event it uses.
> +
> + This event does not replace wl_buffer.release events; servers are still
> + required to send those events.
> +
> + Once a buffer release object has delivered a 'fenced_release' or an
> + 'immediate_release' event it is automatically destroyed.
> + </description>
> +
> + <event name="fenced_release">
> + <description summary="release buffer with fence">
> + Sent when the compositor has finalised its usage of the associated
> + buffer for the relevant commit, providing a dma_fence which will be
> + signaled when all operations by the compositor on that buffer for that
> + commit have finished.
It wouldn't hurt to repeat here:
"This event destroys the zwp_buffer_release_v1 object."
> + </description>
> + <arg name="fence" type="fd" summary="fence for last operation on buffer"/>
> + </event>
> +
> + <event name="immediate_release">
> + <description summary="release buffer immediately">
> + Sent when the compositor has finalised its usage of the associated
> + buffer for the relevant commit, and either performed no operations
> + using it, or has a guarantee that all its operations on that buffer for
> + that commit have finished.
And here.
> + </description>
> + </event>
> + </interface>
> +
> +</protocol>
Looks very good. One more minor revision, and I'll start a one day
count-down to merge this.
Thanks,
pq
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