drm/syncobj: add timeline point merger utility

include/render/drm_syncobj_merger.h

@@ -0,0 +1,44 @@
+#ifndef WLR_RENDER_DRM_SYNCOBJ_MERGER_H
+#define WLR_RENDER_DRM_SYNCOBJ_MERGER_H
+
+#include <wayland-server-core.h>
+
+/**
+ * Accumulate timeline points, to have a destination timeline point be
+ * signalled when all inputs are
+ */
+struct wlr_drm_syncobj_merger {
+	int n_ref;
+	struct wlr_drm_syncobj_timeline *dst_timeline;
+	uint64_t dst_point;
+	int sync_fd;
+};
+
+/**
+ * Create a new merger.
+ *
+ * The given timeline point will be signalled when all input points are
+ * signalled and the merger is destroyed.
+ */
+struct wlr_drm_syncobj_merger *wlr_drm_syncobj_merger_create(
+	struct wlr_drm_syncobj_timeline *dst_timeline, uint64_t dst_point);
+
+struct wlr_drm_syncobj_merger *wlr_drm_syncobj_merger_ref(
+	struct wlr_drm_syncobj_merger *merger);
+
+/**
+ * Target timeline point is materialized when all inputs are, and the merger is
+ * destroyed.
+ */
+void wlr_drm_syncobj_merger_unref(struct wlr_drm_syncobj_merger *merger);
+/**
+ * Add a new timeline point to wait for.
+ *
+ * If the point is not materialized, the supplied event loop is used to schedule
+ * a wait.
+ */
+bool wlr_drm_syncobj_merger_add(struct wlr_drm_syncobj_merger *merger,
+	struct wlr_drm_syncobj_timeline *dst_timeline, uint64_t dst_point,
+	struct wl_event_loop *loop);
+
+#endif

render/drm_syncobj_merger.c

@@ -0,0 +1,130 @@
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <wayland-util.h>
+#include <wlr/render/drm_syncobj.h>
+#include <wlr/util/log.h>
+#include <xf86drm.h>
+#include "render/drm_syncobj_merger.h"
+
+#include "config.h"
+
+#if HAVE_LINUX_SYNC_FILE
+
+#include <linux/sync_file.h>
+#include <sys/ioctl.h>
+
+static int sync_file_merge(int fd1, int fd2) {
+	// The kernel will automatically prune signalled fences
+	struct sync_merge_data merge_data = { .fd2 = fd2 };
+	if (ioctl(fd1, SYNC_IOC_MERGE, &merge_data) < 0) {
+		wlr_log_errno(WLR_ERROR, "ioctl(SYNC_IOC_MERGE) failed");
+		return -1;
+	}
+
+	return merge_data.fence;
+}
+
+#else
+
+static int sync_file_merge(int fd1, int fd2) {
+	wlr_log(WLR_ERROR, "sync_file support is unavailable");
+	return -1;
+}
+
+#endif
+
+struct wlr_drm_syncobj_merger *wlr_drm_syncobj_merger_create(
+		struct wlr_drm_syncobj_timeline *dst_timeline, uint64_t dst_point) {
+	struct wlr_drm_syncobj_merger *merger = calloc(1, sizeof(*merger));
+	if (merger == NULL) {
+		return NULL;
+	}
+	merger->n_ref = 1;
+	merger->dst_timeline = wlr_drm_syncobj_timeline_ref(dst_timeline);
+	merger->dst_point = dst_point;
+	merger->sync_fd = -1;
+	return merger;
+}
+
+struct wlr_drm_syncobj_merger *wlr_drm_syncobj_merger_ref(
+		struct wlr_drm_syncobj_merger *merger) {
+	assert(merger->n_ref > 0);
+	merger->n_ref++;
+	return merger;
+}
+
+void wlr_drm_syncobj_merger_unref(struct wlr_drm_syncobj_merger *merger) {
+	assert(merger->n_ref > 0);
+	merger->n_ref--;
+	if (merger->n_ref > 0) {
+		return;
+	}
+
+	if (merger->sync_fd != -1) {
+		wlr_drm_syncobj_timeline_import_sync_file(merger->dst_timeline,
+			merger->dst_point, merger->sync_fd);
+		close(merger->sync_fd);
+	} else {
+		wlr_drm_syncobj_timeline_signal(merger->dst_timeline, merger->dst_point);
+	}
+	wlr_drm_syncobj_timeline_unref(merger->dst_timeline);
+	free(merger);
+}
+
+static bool merger_add_exportable(struct wlr_drm_syncobj_merger *merger,
+		struct wlr_drm_syncobj_timeline *src_timeline, uint64_t src_point) {
+	int new_sync = wlr_drm_syncobj_timeline_export_sync_file(src_timeline, src_point);
+	if (merger->sync_fd != -1) {
+		int fd2 = new_sync;
+		new_sync = sync_file_merge(merger->sync_fd, fd2);
+		close(fd2);
+		close(merger->sync_fd);
+	}
+	merger->sync_fd = new_sync;
+	return true;
+}
+
+struct export_waiter {
+	struct wlr_drm_syncobj_timeline_waiter waiter;
+	struct wlr_drm_syncobj_merger *merger;
+	struct wlr_drm_syncobj_timeline *src_timeline;
+	uint64_t src_point;
+};
+
+static void export_waiter_handle_ready(struct wlr_drm_syncobj_timeline_waiter *waiter) {
+	struct export_waiter *add = wl_container_of(waiter, add, waiter);
+	merger_add_exportable(add->merger, add->src_timeline, add->src_point);
+	wlr_drm_syncobj_merger_unref(add->merger);
+	wlr_drm_syncobj_timeline_unref(add->src_timeline);
+	wlr_drm_syncobj_timeline_waiter_finish(&add->waiter);
+	free(add);
+}
+
+bool wlr_drm_syncobj_merger_add(struct wlr_drm_syncobj_merger *merger,
+		struct wlr_drm_syncobj_timeline *src_timeline, uint64_t src_point,
+		struct wl_event_loop *loop) {
+	assert(loop != NULL);
+	bool exportable = false;
+	int flags = DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE;
+	if (!wlr_drm_syncobj_timeline_check(src_timeline, src_point, flags, &exportable)) {
+		return false;
+	}
+	if (exportable) {
+		return merger_add_exportable(merger, src_timeline, src_point);
+	}
+	struct export_waiter *add = calloc(1, sizeof(*add));
+	if (add == NULL) {
+		return false;
+	}
+	if (!wlr_drm_syncobj_timeline_waiter_init(&add->waiter, src_timeline, src_point,
+			flags, loop, export_waiter_handle_ready)) {
+		return false;
+	}
+	add->merger = merger;
+	add->src_timeline = wlr_drm_syncobj_timeline_ref(src_timeline);
+	add->src_point = src_point;
+	merger->n_ref++;
+	return true;
+}

render/meson.build

@@ -9,6 +9,7 @@ wlr_files += files(
 	'color.c',
 	'dmabuf.c',
 	'drm_format_set.c',
+	'drm_syncobj_merger.c',
 	'drm_syncobj.c',
 	'pass.c',
 	'pixel_format.c',
@@ -28,6 +29,7 @@ else
 endif
 
 internal_config.set10('HAVE_EVENTFD', cc.has_header('sys/eventfd.h'))
+internal_config.set10('HAVE_LINUX_SYNC_FILE', cc.has_header('linux/sync_file.h'))
 
 if 'gles2' in renderers or 'auto' in renderers
 	egl = dependency('egl', required: 'gles2' in renderers)