[PATCH wayland-protocols] Add zwp_linux_explicit_synchronization_v1
Matt Hoosier
matt.hoosier at gmail.com
Wed Sep 20 12:48:26 UTC 2017
On Tue, Sep 19, 2017 at 6:46 PM, Daniel Stone <daniels at collabora.com> wrote:
> Signed-off-by: Daniel Stone <daniels at collabora.com>
> ---
> Makefile.am | 1 +
> unstable/linux-explicit-synchronization/README | 5 +
> .../linux-explicit-synchronization-unstable-v1.xml | 208 +++++++++++++++++++++
> 3 files changed, 214 insertions(+)
> create mode 100644 unstable/linux-explicit-synchronization/README
> create mode 100644 unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml
>
> diff --git a/Makefile.am b/Makefile.am
> index 5b5ae96..941692c 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -15,6 +15,7 @@ unstable_protocols = \
> unstable/xwayland-keyboard-grab/xwayland-keyboard-grab-unstable-v1.xml \
> unstable/keyboard-shortcuts-inhibit/keyboard-shortcuts-inhibit-unstable-v1.xml \
> unstable/xdg-output/xdg-output-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..fac116f
> --- /dev/null
> +++ b/unstable/linux-explicit-synchronization/README
> @@ -0,0 +1,5 @@
> +Linux explicit synchronization (dma-fence) protocol
> +
> +Maintainers:
> +David Reveman <reveman at chromium.org>
> +Daniel Stone <daniels 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..4a6636e
> --- /dev/null
> +++ b/unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml
> @@ -0,0 +1,208 @@
> +<?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
> +
> + 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.
> +
> + Explicit 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.
> + 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. This is referred
> + to as 'implicit synchronization'.
> +
> + By contrast, explicit synchronization takes dma_fence objects as a
> + marker of when the asynchronous operations are complete. The fence
> + provided by the client will be waited on before the compositor
> + accesses the buffer. Conversely, in place of wl_buffer.release
> + events, the Wayland server will inform the client when the buffer
> + can be destructively accessed through a zwp_buffer_release_v1
> + object.
> +
> + This interface cannot be instantiated multiple times for a single
> + surface, and as such should only be used by the component which
> + performs the wl_surface.attach request. Whenever control of
> + buffer attachments is released, the releasing component should
> + ensure it destroys the zwp_surface_synchronization_v1 object.
> +
> + It is illegal to destroy a zwp_surface_synchronization_v1 object
> + after its wl_surface has been destroyed.
> + </description>
> +
> + <request name="destroy" type="destructor">
> + <description summary="destroy synchronization object">
> + Destroy this explicit synchronization object.
> +
> + 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"/>
> + </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
> + 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.
> +
> + If the fence could not be imported, an INVALID_FENCE error is signaled
> + to the client.
> +
> + If a fence has already been attached during the same commit cycle,
> + a DUPLICATE_FENCE error is signaled to the client.
> + </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
> + documentation for more information.
> +
> + The release object is double-buffered state, and will be applied
> + on the next wl_surface.commit request for the associated surface.
> +
> + 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.
> + </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 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
> + where relevant for the client to synchronize against before reusing
> + the buffer.
> +
> + This event does not replace wl_buffer.release events; servers are still
> + required to send those events.
> + </description>
> +
> + <request name="destroy" type="destructor">
> + <description summary="destroy buffer release synchronization object">
> + Destroy this buffer release explicit synchronization object. The object
> + may be destroyed at any time.
> + </description>
> + </request>
> +
> + <event name="fenced_release">
> + <description summary="release buffer with fence">
> + Sent when the compositor has finalised its usage of the associated
> + buffer, providing a dma_fence which will be signaled when all
> + operations by the compositor on that buffer have finished.
> +
> + Clients must not perform any destructive operations (e.g. clearing or
> + rendering) on the buffer until that fence has passed. They may,
> + however, destroy the wl_buffer 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, and either performed no operations using it, or has a
> + guarantee that all its operations have finished and no more external
> + effects will be observed from these operations.
> + </description>
> + </event>
> + </interface>
> +
> +</protocol>
> --
> 2.14.1
On a related subject, there was discussion back at
https://lists.freedesktop.org/archives/wayland-devel/2013-September/011091.html
that acknowledged a longstanding bug where wl_buffer::release events
are starved indefinitely in the outbound server socket if there
doesn't happen to be any frame callback installed. That discussion
petered out, but it looked like there was a consensus that the issue
should be fixed (post the WL_BUFFER_RELEASE immediately rather than
queue if no frame callbacks attached).
That seems like a good issue to get closed up. Any objections to
reviving the patch along the lines that Pekka suggested?
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