Wayland generic dmabuf protocol
Pekka Paalanen
pekka.paalanen at collabora.co.uk
Fri Jun 6 08:30:20 PDT 2014
Hi,
the previous attempt at introducing a generic wl_dmabuf protocol to
Wayland didn't end too well:
http://lists.freedesktop.org/archives/wayland-devel/2013-December/012390.html
http://lists.freedesktop.org/archives/wayland-devel/2013-December/012455.html
http://lists.freedesktop.org/archives/wayland-devel/2013-December/012566.html
http://lists.freedesktop.org/archives/wayland-devel/2014-January/012727.html
We are again interested in this, and I did a quick Friday evening draft
to open the discussion again. The base of the draft was a quick look at
https://www.khronos.org/registry/egl/extensions/EXT/EGL_EXT_image_dma_buf_import.txt
The basic idea is, that a client has one or more dmabufs it wants to
share with the compositor, making up a single logical buffer (a single
image). The client chooses where and how to export those dmabufs. The
dmabuf fds and metadata are sent to the compositor, the compositor
assembles and tries to import them. If the import succeeds, a wl_buffer
object is created. If the import fails, the client is notified that the
compositor can't use these, it would be better to try something else.
I assume that if the "import" succeeds, the compositor is able to use
the buffers, e.g. at least turn them into a GL-texture or mmap them, if
not also able to scan out or put on a hw overlay. This could be any kind
of checking to verify that the buffers are usable. Finding out that it
won't work after the client is already using the wl_buffer must not
happen, as we have no way to recover from it: the client will get
disconnected. So the point is knowing in advance, that the buffers are
usable on both sides, preferrably before the client has filled them with
data, but I suppose in the usual case the buffer is already filled.
As creating a dmabuf-based wl_buffer requires a roundtrip in this
scheme, I assume it only needs to be done rarely, and the same buffer
can be re-used many times with proper synchronization.
The crude draft is below. Some questions:
- Does this sound sane to you?
- What other metadata would we need? Thierry had some issues with
tiling formats I think.
- This "check if the dmabuf is really usable" is needed, right? We
can't just assume that any dmabuf will work?
- Do we need anything for fences here, or is the dmabuf fd enough?
- Does someone already have something similar running?
Thanks,
pq
From b868dd816c38ec6e3741970cf3a29006fd10a263 Mon Sep 17 00:00:00 2001
From: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
Date: Fri, 6 Jun 2014 17:56:41 +0300
Subject: [PATCH weston] protocol: linux_dmabuf RFC
---
protocol/linux-dmabuf.xml | 188 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 188 insertions(+)
create mode 100644 protocol/linux-dmabuf.xml
diff --git a/protocol/linux-dmabuf.xml b/protocol/linux-dmabuf.xml
new file mode 100644
index 0000000..643e5ca
--- /dev/null
+++ b/protocol/linux-dmabuf.xml
@@ -0,0 +1,188 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<protocol name="linux-dmabuf">
+
+ <copyright>
+ Copyright © 2008-2011 Kristian Høgsberg
+ Copyright © 2010-2011 Intel Corporation
+ Copyright © 2014 Collabora, Ltd.
+
+ Permission to use, copy, modify, distribute, and sell this
+ software and its documentation for any purpose is hereby granted
+ without fee, provided that the above copyright notice appear in
+ all copies and that both that copyright notice and this permission
+ notice appear in supporting documentation, and that the name of
+ the copyright holders not be used in advertising or publicity
+ pertaining to distribution of the software without specific,
+ written prior permission. The copyright holders make no
+ representations about the suitability of this software for any
+ purpose. It is provided "as is" without express or implied
+ warranty.
+
+ THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
+ SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
+ AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
+ ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+ THIS SOFTWARE.
+ </copyright>
+
+ <interface name="_linux_dmabuf_factory" version="1">
+ <description summary="factory for creating dmabuf-based wl_buffers">
+ Following the interfaces from:
+ https://www.khronos.org/registry/egl/extensions/EXT/EGL_EXT_image_dma_buf_import.txt
+
+ This interface offers a way to create generic dmabuf-based
+ wl_buffers.
+ </description>
+
+ <enum name="format">
+ <!-- The drm format codes match the #defines in drm_fourcc.h.
+ The formats actually supported by the compositor will be
+ reported by the format event. -->
+ <entry name="c8" value="0x20203843"/>
+ <entry name="rgb332" value="0x38424752"/>
+ <entry name="bgr233" value="0x38524742"/>
+ <entry name="xrgb4444" value="0x32315258"/>
+ <entry name="xbgr4444" value="0x32314258"/>
+ <entry name="rgbx4444" value="0x32315852"/>
+ <entry name="bgrx4444" value="0x32315842"/>
+ <entry name="argb4444" value="0x32315241"/>
+ <entry name="abgr4444" value="0x32314241"/>
+ <entry name="rgba4444" value="0x32314152"/>
+ <entry name="bgra4444" value="0x32314142"/>
+ <entry name="xrgb1555" value="0x35315258"/>
+ <entry name="xbgr1555" value="0x35314258"/>
+ <entry name="rgbx5551" value="0x35315852"/>
+ <entry name="bgrx5551" value="0x35315842"/>
+ <entry name="argb1555" value="0x35315241"/>
+ <entry name="abgr1555" value="0x35314241"/>
+ <entry name="rgba5551" value="0x35314152"/>
+ <entry name="bgra5551" value="0x35314142"/>
+ <entry name="rgb565" value="0x36314752"/>
+ <entry name="bgr565" value="0x36314742"/>
+ <entry name="rgb888" value="0x34324752"/>
+ <entry name="bgr888" value="0x34324742"/>
+ <entry name="xrgb8888" value="0x34325258"/>
+ <entry name="xbgr8888" value="0x34324258"/>
+ <entry name="rgbx8888" value="0x34325852"/>
+ <entry name="bgrx8888" value="0x34325842"/>
+ <entry name="argb8888" value="0x34325241"/>
+ <entry name="abgr8888" value="0x34324241"/>
+ <entry name="rgba8888" value="0x34324152"/>
+ <entry name="bgra8888" value="0x34324142"/>
+ <entry name="xrgb2101010" value="0x30335258"/>
+ <entry name="xbgr2101010" value="0x30334258"/>
+ <entry name="rgbx1010102" value="0x30335852"/>
+ <entry name="bgrx1010102" value="0x30335842"/>
+ <entry name="argb2101010" value="0x30335241"/>
+ <entry name="abgr2101010" value="0x30334241"/>
+ <entry name="rgba1010102" value="0x30334152"/>
+ <entry name="bgra1010102" value="0x30334142"/>
+ <entry name="yuyv" value="0x56595559"/>
+ <entry name="yvyu" value="0x55595659"/>
+ <entry name="uyvy" value="0x59565955"/>
+ <entry name="vyuy" value="0x59555956"/>
+ <entry name="ayuv" value="0x56555941"/>
+ <entry name="nv12" value="0x3231564e"/>
+ <entry name="nv21" value="0x3132564e"/>
+ <entry name="nv16" value="0x3631564e"/>
+ <entry name="nv61" value="0x3136564e"/>
+ <entry name="yuv410" value="0x39565559"/>
+ <entry name="yvu410" value="0x39555659"/>
+ <entry name="yuv411" value="0x31315559"/>
+ <entry name="yvu411" value="0x31315659"/>
+ <entry name="yuv420" value="0x32315559"/>
+ <entry name="yvu420" value="0x32315659"/>
+ <entry name="yuv422" value="0x36315559"/>
+ <entry name="yvu422" value="0x36315659"/>
+ <entry name="yuv444" value="0x34325559"/>
+ <entry name="yvu444" value="0x34325659"/>
+ </enum>
+
+ <request name="destroy" type="destructor">
+ <description summary="unbind the factory">
+ </description>
+ </request>
+
+ <request name="create_buffer">
+ <description summary="start creating a wl_buffer">
+ Any errors are returned in the dmabuf_proxy object as non-fatal.
+ </description>
+ <arg name="stub" type="new_id" interface="dmabuf_proxy"/>
+ <arg name="width" type="int"/>
+ <arg name="height" type="int"/>
+ <arg name="format" type="uint" summary="from format enum"/>
+ </request>
+ </interface>
+
+ <interface name="dmabuf_proxy" version="1">
+ <description summary="a placeholder logical buffer object">
+ As a logical buffer cannot always be create in a single
+ request, this object acts as a temporary logical buffer object,
+ that in the end will be turned into a wl_buffer object.
+
+ If the server cannot handle the set of dmabufs and the other
+ arguments, a non-fatal error is returned instead of the
+ new wl_buffer object. After either reply, this temporary object
+ must be destroyed.
+ </description>
+
+ <enum name="error">
+ <entry name="invalid_format" value="1"/>
+ <entry name="invalid_name" value="2"/>
+ </enum>
+
+ <request name="add_dmabuf">
+ <description summary="add a dmabuf to the wl_buffer">
+ Multi-planar formats may require using more than one
+ dmabuf for passing all the data for one logical buffer.
+ This request adds one dmabuf to the set in this dmabuf_proxy.
+
+ When one dmabuf has several planar channels, offset1 & stride1 and
+ offset2 and stride2 must be used to denote them without sending a
+ new add_dmabuf request which would create a new fd in the server
+ while still pointing at the same dmabuf.
+
+ offset0 and stride0 must always be set. Other unused offsets and
+ strides must be zero.
+ </description>
+ <arg name="name" type="fd"/>
+ <arg name="offset0" type="int"/>
+ <arg name="stride0" type="int"/>
+ <arg name="offset1" type="int"/>
+ <arg name="stride1" type="int"/>
+ <arg name="offset2" type="int"/>
+ <arg name="stride2" type="int"/>
+ </request>
+
+ <request name="finish">
+ <description summary="finish creating the wl_buffer">
+ This tells the server that all dmabufs have been added,
+ and the server can proceed creating the wl_buffer.
+ The server will reply with an event, either "created" or "failed".
+ </description>
+ </request>
+
+ <event name="created">
+ <description summary="the wl_buffer was created">
+ The server has registered and tested the set of dmabufs, the format,
+ etc. and found that it can use the resulting buffer.
+
+ The dmabuf_proxy object must be destroyed, and not used again.
+ </description>
+ <arg name="id" type="new_id" interface="wl_buffer"
+ summary="the new wl_buffer"/>
+ </event>
+
+ <event name="failed">
+ <description summary="finish creating the wl_buffer">
+ The dmabuf_proxy object must be destroyed, and not used again.
+ </description>
+ <!-- TODO: add some failure indicators: bad dmabuf, format, incomplete...
+ -->
+ </event>
+
+ </interface>
+</protocol>
--
1.8.5.5
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