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render/drm_syncobj: introduce wlr_drm_syncobj_timeline

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wlr_drm_syncobj_timeline is a synchronization primitive based on
drm_syncobj timelines. They are heavily inspired from Vulkan
timeline semaphores [1].

[1]: https://www.khronos.org/blog/vulkan-timeline-semaphores
This commit is contained in:
Simon Ser 2021-10-20 18:47:46 +02:00
parent f464213447
commit 7fc00ef777
3 changed files with 170 additions and 0 deletions
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71
include/wlr/render/drm_syncobj.h Normal file
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#ifndef WLR_RENDER_DRM_SYNCOBJ_H
#define WLR_RENDER_DRM_SYNCOBJ_H
#include <stdbool.h>
#include <stdint.h>
/**
* A synchronization timeline.
*
* Timelines are used to synchronize accesses to buffers. Given a producer
* (writing contents to a buffer) and a consumer (reading from the buffer), the
* compositor needs to synchronize back-and-forth between these two users. The
* consumer needs to wait for the producer to signal that they're done with the
* writes, and the producer needs to wait for the consumer to signal that
* they're done with the reads.
*
* Timelines provide synchronization points in the form of monotonically
* increasing 64-bit integer values.
*
* wlroots timelines are designed after Vulkan timeline semaphores. For more
* information on the Vulkan APIs, see:
* https://www.khronos.org/blog/vulkan-timeline-semaphores
*
* wlroots timelines are powered by DRM synchronization objects (drm_syncobj):
* https://dri.freedesktop.org/docs/drm/gpu/drm-mm.html#drm-sync-objects
*/
struct wlr_drm_syncobj_timeline {
int drm_fd;
uint32_t handle;
// private state
size_t n_refs;
};
/**
* Create a new synchronization timeline.
*/
struct wlr_drm_syncobj_timeline *wlr_drm_syncobj_timeline_create(int drm_fd);
/**
* Reference a synchronization timeline.
*/
struct wlr_drm_syncobj_timeline *wlr_drm_syncobj_timeline_ref(struct wlr_drm_syncobj_timeline *timeline);
/**
* Unreference a synchronization timeline.
*/
void wlr_drm_syncobj_timeline_unref(struct wlr_drm_syncobj_timeline *timeline);
/**
* Export a timeline point as a sync_file FD.
*
* The returned sync_file will be signalled when the provided point is
* signalled on the timeline.
*
* This allows inter-operation with other APIs which don't support drm_syncobj
* yet. The synchronization point needs to have already materialized:
* wait-before-signal is not supported.
*/
int wlr_drm_syncobj_timeline_export_sync_file(struct wlr_drm_syncobj_timeline *timeline,
uint64_t src_point);
/**
* Import a timeline point from a sync_file FD.
*
* The provided timeline point will be signalled when the provided sync_file is.
*
* This allows inter-operation with other APIs which don't support drm_syncobj
* yet.
*/
bool wlr_drm_syncobj_timeline_import_sync_file(struct wlr_drm_syncobj_timeline *timeline,
uint64_t dst_point, int sync_file_fd);
#endif