An experimental (hence the 'z' prefix) linux_dmabuf Wayland protocol extension for creating dmabuf-based wl_buffers in a generic manner. This does not include proper dmabuf metadata negotiation because there is no way to communicate all dmabuf constraints from the compositor to a client before-hand. The client has to create a wl_buffer wrapping one or more dmabuf buffers and then listen at the feedback object returned to know if the operation was successful. RFCv1 changes (after a first draft without code): - some renames of interfaces and argument, no semantic changes - added destructor protocol to dmabuf_batch - added feedback interface for buffer creation v2 changes: - use drm_fourcc.h as authoritative source for format codes - add support for the 64-bit layout qualifier and y-inverted dmabufs - simplify the 'add' request (no need to preserve fd numerical id) - add explicit plane index in the 'add' request - integrate the 'feedback' object events to the batch interface - rename 'create_buffer' to 'create' and move it into the batch interface - add requirements needed from the graphics stack and clients - improve existing errors and add batch error codes - removed error codes from the global interface - improve documentation for arguments, enums, etc. - rename dmabuf_batch to zlinux_buffer_params - The y-inverted property makes more sense as a whole buffer property. Y-flipping individual planes of the same buffer object is hardly useful. The y-invert is also converted into a flag, so we may add more flags later. - add flags for interlaced buffer content v3 changes: - Apply Daniel Vetter's comments about wording on coherency. Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk> Signed-off-by: Louis-Francis Ratté-Boulianne <lfrb@collabora.com> Reviewed-by: Daniel Stone <daniels@collabora.com> Acked-by: Benjamin Gaignard <benjamin.gaignard@linaro.org> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>dev
Pekka Paalanen
10 years ago
parent
f3c8336320
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<?xml version="1.0" encoding="UTF-8"?> |
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<protocol name="linux_dmabuf"> |
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|
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<copyright> |
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Copyright © 2014, 2015 Collabora, Ltd. |
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|
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Permission to use, copy, modify, distribute, and sell this |
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software and its documentation for any purpose is hereby granted |
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without fee, provided that the above copyright notice appear in |
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all copies and that both that copyright notice and this permission |
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notice appear in supporting documentation, and that the name of |
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the copyright holders not be used in advertising or publicity |
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pertaining to distribution of the software without specific, |
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written prior permission. The copyright holders make no |
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representations about the suitability of this software for any |
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purpose. It is provided "as is" without express or implied |
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warranty. |
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|
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THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS |
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SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND |
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FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY |
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SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN |
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AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, |
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ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF |
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THIS SOFTWARE. |
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</copyright> |
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|
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<interface name="zlinux_dmabuf" version="1"> |
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<description summary="factory for creating dmabuf-based wl_buffers"> |
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Following the interfaces from: |
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https://www.khronos.org/registry/egl/extensions/EXT/EGL_EXT_image_dma_buf_import.txt |
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and the Linux DRM sub-system's AddFb2 ioctl. |
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|
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This interface offers a way to create generic dmabuf-based |
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wl_buffers. Immediately after a client binds to this interface, |
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the set of supported formats is sent with 'format' events. |
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|
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The following are required from clients: |
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|
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- Clients must ensure that either all data in the dma-buf is |
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coherent for all subsequent read access or that coherency is |
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correctly handled by the underlying kernel-side dma-buf |
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implementation. |
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|
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- Don't make any more attachments after sending the buffer to the |
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compositor. Making more attachments later increases the risk of |
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the compositor not being able to use (re-import) an existing |
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dmabuf-based wl_buffer. |
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|
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The underlying graphics stack must ensure the following: |
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|
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- The dmabuf file descriptors relayed to the server will stay valid |
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for the whole lifetime of the wl_buffer. This means the server may |
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at any time use those fds to import the dmabuf into any kernel |
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sub-system that might accept it. |
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|
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To create a wl_buffer from one or more dmabufs, a client creates a |
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zlinux_dmabuf_params object with zlinux_dmabuf.create_params |
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request. All planes required by the intended format are added with |
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the 'add' request. Finally, 'create' request is issued. The server |
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will reply with either 'created' event which provides the final |
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wl_buffer or 'failed' event saying that it cannot use the dmabufs |
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provided. |
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</description> |
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|
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<request name="destroy" type="destructor"> |
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<description summary="unbind the factory"> |
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Objects created through this interface, especially wl_buffers, will |
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remain valid. |
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</description> |
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</request> |
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|
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<request name="create_params"> |
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<description summary="create a temporary object for buffer parameters"> |
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This temporary object is used to collect multiple dmabuf handles into |
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a single batch to create a wl_buffer. It can only be used once and |
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should be destroyed after an 'created' or 'failed' event has been |
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received. |
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</description> |
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<arg name="params_id" type="new_id" interface="zlinux_buffer_params" |
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summary="the new temporary"/> |
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</request> |
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|
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<event name="format"> |
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<description summary="supported buffer format"> |
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This event advertises one buffer format that the server supports. |
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All the supported formats are advertised once when the client |
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binds to this interface. A roundtrip after binding guarantees, |
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that the client has received all supported formats. |
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For the definition of the format codes, see create request. |
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XXX: Can a compositor ever enumerate them? |
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</description> |
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<arg name="format" type="uint" summary="DRM_FORMAT code"/> |
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</event> |
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|
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</interface> |
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|
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<interface name="zlinux_buffer_params" version="1"> |
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<description summary="parameters for creating a dmabuf-based wl_buffer"> |
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This temporary object is a collection of dmabufs and other |
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parameters that together form a single logical buffer. The temporary |
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object may eventually create one wl_buffer unless cancelled by |
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destroying it before requesting 'create'. |
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|
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Single-planar formats only require one dmabuf, however |
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multi-planar formats may require more than one dmabuf. For all |
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formats, 'add' request must be called once per plane (even if the |
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underlying dmabuf fd is identical). |
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|
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You must use consecutive plane indices ('plane_idx' argument for 'add') |
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from zero to the number of planes used by the drm_fourcc format code. |
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All planes required by the format must be given exactly once, but can |
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be given in any order. Each plane index can be set only once. |
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</description> |
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|
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<enum name="error"> |
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<entry name="already_used" value="0" |
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summary="the dmabuf_batch object has already been used to create a wl_buffer"/> |
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<entry name="plane_idx" value="1" |
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summary="plane index out of bounds"/> |
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<entry name="plane_set" value="2" |
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summary="the plane index was already set"/> |
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<entry name="incomplete" value="3" |
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summary="missing or too many planes to create a buffer"/> |
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|
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<entry name="invalid_format" value="4" |
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summary="format not supported"/> |
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<entry name="invalid_dimensions" value="5" |
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summary="invalid width or height"/> |
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<entry name="out_of_bounds" value="6" |
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summary="offset + stride * height goes out of dmabuf bounds"/> |
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</enum> |
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|
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<request name="destroy" type="destructor"> |
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<description summary="delete this object, used or not"> |
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Cleans up the temporary data sent to the server for dmabuf-based |
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wl_buffer creation. |
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</description> |
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</request> |
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|
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<request name="add"> |
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<description summary="add a dmabuf to the temporary set"> |
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This request adds one dmabuf to the set in this zlinux_buffer_params. |
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The 64-bit unsigned value combined from modifier_hi and modifier_lo |
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is the dmabuf layout modifier. DRM AddFB2 ioctl calls this the |
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fb modifier, which is defined in drm_mode.h of Linux UAPI. |
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This is an opaque token. Drivers use this token to express tiling, |
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compression, etc. driver-specific modifications to the base format |
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defined by the DRM fourcc code. |
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This request raises the PLANE_IDX error if plane_idx is too large. |
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The error PLANE_SET is raised if attempting to set a plane that |
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was already set. |
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</description> |
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|
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<arg name="fd" type="fd" summary="dmabuf fd"/> |
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<arg name="plane_idx" type="uint" summary="plane index"/> |
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<arg name="offset" type="uint" summary="offset in bytes"/> |
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<arg name="stride" type="uint" summary="stride in bytes"/> |
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<arg name="modifier_hi" type="uint" |
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summary="high 32 bits of layout modifier"/> |
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<arg name="modifier_lo" type="uint" |
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summary="low 32 bits of layout modifier"/> |
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</request> |
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<enum name="flags"> |
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<entry name="y_invert" value="1" summary="contents are y-inverted"/> |
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<entry name="interlaced" value="2" summary="content is interlaced"/> |
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<entry name="bottom_first" value="4" summary="bottom field first"/> |
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</enum> |
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|
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<request name="create"> |
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<description summary="create a wl_buffer from the given dmabufs"> |
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This asks for creation of a wl_buffer from the added dmabuf |
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buffers. The wl_buffer is not created immediately but returned via |
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the 'created' event if the dmabuf sharing succeeds. The sharing |
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may fail at runtime for reasons a client cannot predict, in |
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which case the 'failed' event is triggered. |
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|
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The 'format' argument is a DRM_FORMAT code, as defined by the |
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libdrm's drm_fourcc.h. The Linux kernel's DRM sub-system is the |
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authoritative source on how the format codes should work. |
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The 'flags' is a bitfield of the flags defined in enum "flags". |
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'y_invert' means the that the image needs to be y-flipped. |
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Flag 'interlaced' means that the frame in the buffer is not |
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progressive as usual, but interlaced. An interlaced buffer as |
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supported here must always contain both top and bottom fields. |
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The top field always begins on the first pixel row. The temporal |
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ordering between the two fields is top field first, unless |
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'bottom_first' is specified. It is undefined whether 'bottom_first' |
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is ignored if 'interlaced' is not set. |
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|
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This protocol does not convey any information about field rate, |
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duration, or timing, other than the relative ordering between the |
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two fields in one buffer. A compositor may have to estimate the |
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intended field rate from the incoming buffer rate. It is undefined |
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whether the time of receiving wl_surface.commit with a new buffer |
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attached, applying the wl_surface state, wl_surface.frame callback |
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trigger, presentation, or any other point in the compositor cycle |
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is used to measure the frame or field times. There is no support |
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for detecting missed or late frames/fields/buffers either, and |
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there is no support whatsoever for cooperating with interlaced |
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compositor output. |
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The composited image quality resulting from the use of interlaced |
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buffers is explicitly undefined. A compositor may use elaborate |
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hardware features or software to deinterlace and create progressive |
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output frames from a sequence of interlaced input buffers, or it |
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may produce substandard image quality. However, compositors that |
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cannot guarantee reasonable image quality in all cases are recommended |
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to just reject all interlaced buffers. |
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|
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Any argument errors, including non-positive width or height, |
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mismatch between the number of planes and the format, bad |
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format, bad offset or stride, may be indicated by fatal protocol |
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errors: INCOMPLETE, INVALID_FORMAT, INVALID_DIMENSIONS, |
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OUT_OF_BOUNDS. |
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Dmabuf import errors in the server that are not obvious client |
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bugs are returned via the 'failed' event as non-fatal. This |
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allows attempting dmabuf sharing and falling back in the client |
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if it fails. |
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This request can be sent only once in the object's lifetime, after |
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which the only legal request is destroy. This object should be |
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destroyed after issuing 'create' request. Attempting to use this |
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object after issuing 'create' raises ALREADY_USED protocol error. |
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It is not mandatory to issue 'create'. If a client wants to |
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cancel the buffer creation, it can just destroy this object. |
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</description> |
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<arg name="width" type="int" summary="base plane width in pixels"/> |
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<arg name="height" type="int" summary="base plane height in pixels"/> |
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<arg name="format" type="uint" summary="DRM_FORMAT code"/> |
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<arg name="flags" type="uint" summary="see enum flags"/> |
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</request> |
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<event name="created"> |
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<description summary="buffer creation succeeded"> |
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This event indicates that the attempted buffer creation was |
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successful. It provides the new wl_buffer referencing the dmabuf(s). |
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Upon receiving this event, the client should destroy the |
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zlinux_dmabuf_params object. |
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</description> |
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<arg name="buffer" type="new_id" interface="wl_buffer" |
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summary="the newly created wl_buffer"/> |
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</event> |
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<event name="failed"> |
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<description summary="buffer creation failed"> |
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This event indicates that the attempted buffer creation has |
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failed. It usually means that one of the dmabuf constraints |
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has not been fulfilled. |
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Upon receiving this event, the client should destroy the |
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zlinux_buffer_params object. |
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</description> |
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</event> |
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</interface> |
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</protocol> |
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Reference in new issue