output: add explicit sync API

include/wlr/types/wlr_output.h

@@ -66,6 +66,8 @@ enum wlr_output_state_field {
 	WLR_OUTPUT_STATE_RENDER_FORMAT = 1 << 8,
 	WLR_OUTPUT_STATE_SUBPIXEL = 1 << 9,
 	WLR_OUTPUT_STATE_LAYERS = 1 << 10,
+	WLR_OUTPUT_STATE_WAIT_TIMELINE = 1 << 11,
+	WLR_OUTPUT_STATE_SIGNAL_TIMELINE = 1 << 12,
 };
 
 enum wlr_output_state_mode_type {
@@ -109,6 +111,11 @@ struct wlr_output_state {
 
 	struct wlr_output_layer_state *layers;
 	size_t layers_len;
+
+	struct wlr_drm_syncobj_timeline *wait_timeline;
+	uint64_t wait_point;
+	struct wlr_drm_syncobj_timeline *signal_timeline;
+	uint64_t signal_point;
 };
 
 struct wlr_output_impl;
@@ -162,6 +169,8 @@ struct wlr_output {
 
 	// true for example with VR headsets
 	bool non_desktop;
+	// Whether wait/signal timelines are supported
+	bool timeline;
 
 	// Commit sequence number. Incremented on each commit, may overflow.
 	uint32_t commit_seq;
@@ -536,6 +545,33 @@ void wlr_output_state_set_damage(struct wlr_output_state *state,
  */
 void wlr_output_state_set_layers(struct wlr_output_state *state,
 	struct wlr_output_layer_state *layers, size_t layers_len);
+/**
+ * Set a timeline point to wait on before displaying the next frame.
+ *
+ * Committing a wait timeline point without a buffer is invalid.
+ *
+ * There is only a single wait timeline point, waiting for multiple timeline
+ * points is unsupported.
+ *
+ * Support for this feature is advertised by the timeline field in
+ * struct wlr_output.
+ */
+void wlr_output_state_set_wait_timeline(struct wlr_output_state *state,
+	struct wlr_drm_syncobj_timeline *timeline, uint64_t src_point);
+/**
+ * Set a timeline point to be signalled when the frame is no longer being used
+ * by the backend.
+ *
+ * Committing a signal timeline point without a buffer is invalid.
+ *
+ * There is only a single signal timeline point, signalling multiple timeline
+ * points is unsupported.
+ *
+ * Support for this feature is advertised by the timeline field in
+ * struct wlr_output.
+ */
+void wlr_output_state_set_signal_timeline(struct wlr_output_state *state,
+	struct wlr_drm_syncobj_timeline *timeline, uint64_t dst_point);
 
 /**
  * Copies the output state from src to dst. It is safe to then

types/output/output.c

@@ -563,10 +563,20 @@ static bool output_basic_test(struct wlr_output *output,
 			wlr_log(WLR_DEBUG, "Primary buffer size mismatch");
 			return false;
 		}
-	} else if (state->tearing_page_flip) {
-		wlr_log(WLR_ERROR, "Trying to commit a tearing page flip without a buffer?");
+	} else {
+		if (state->tearing_page_flip) {
+			wlr_log(WLR_ERROR, "Tried to commit a tearing page flip without a buffer");
+			return false;
+		}
+		if (state->committed & WLR_OUTPUT_STATE_WAIT_TIMELINE) {
+			wlr_log(WLR_DEBUG, "Tried to set wait timeline without a buffer");
+			return false;
+		}
+		if (state->committed & WLR_OUTPUT_STATE_SIGNAL_TIMELINE) {
+			wlr_log(WLR_DEBUG, "Tried to set signal timeline without a buffer");
 			return false;
 		}
+	}
 
 	if (state->committed & WLR_OUTPUT_STATE_RENDER_FORMAT) {
 		struct wlr_allocator *allocator = output->allocator;
@@ -632,6 +642,12 @@ static bool output_basic_test(struct wlr_output *output,
 		}
 	}
 
+	if ((state->committed & (WLR_OUTPUT_STATE_WAIT_TIMELINE | WLR_OUTPUT_STATE_SIGNAL_TIMELINE)) &&
+			!output->timeline) {
+		wlr_log(WLR_DEBUG, "Wait/signal timelines are not supported for this output");
+		return false;
+	}
+
 	return true;
 }
 

types/output/state.c

@@ -1,5 +1,6 @@
 #include <stdlib.h>
 #include <string.h>
+#include <wlr/render/drm_syncobj.h>
 #include <wlr/util/log.h>
 #include "types/wlr_output.h"
 
@@ -16,6 +17,8 @@ void wlr_output_state_finish(struct wlr_output_state *state) {
 	state->buffer = NULL;
 	pixman_region32_fini(&state->damage);
 	free(state->gamma_lut);
+	wlr_drm_syncobj_timeline_unref(state->wait_timeline);
+	wlr_drm_syncobj_timeline_unref(state->signal_timeline);
 }
 
 void wlr_output_state_set_enabled(struct wlr_output_state *state,
@@ -114,16 +117,36 @@ void wlr_output_state_set_layers(struct wlr_output_state *state,
 	state->layers_len = layers_len;
 }
 
+void wlr_output_state_set_wait_timeline(struct wlr_output_state *state,
+		struct wlr_drm_syncobj_timeline *timeline, uint64_t src_point) {
+	state->committed |= WLR_OUTPUT_STATE_WAIT_TIMELINE;
+	wlr_drm_syncobj_timeline_unref(state->wait_timeline);
+	state->wait_timeline = wlr_drm_syncobj_timeline_ref(timeline);
+	state->wait_point = src_point;
+}
+
+void wlr_output_state_set_signal_timeline(struct wlr_output_state *state,
+		struct wlr_drm_syncobj_timeline *timeline, uint64_t dst_point) {
+	state->committed |= WLR_OUTPUT_STATE_SIGNAL_TIMELINE;
+	wlr_drm_syncobj_timeline_unref(state->signal_timeline);
+	state->signal_timeline = wlr_drm_syncobj_timeline_ref(timeline);
+	state->signal_point = dst_point;
+}
+
 bool wlr_output_state_copy(struct wlr_output_state *dst,
 		const struct wlr_output_state *src) {
 	struct wlr_output_state copy = *src;
 	copy.committed &= ~(WLR_OUTPUT_STATE_BUFFER |
 		WLR_OUTPUT_STATE_DAMAGE |
-		WLR_OUTPUT_STATE_GAMMA_LUT);
+		WLR_OUTPUT_STATE_GAMMA_LUT |
+		WLR_OUTPUT_STATE_WAIT_TIMELINE |
+		WLR_OUTPUT_STATE_SIGNAL_TIMELINE);
 	copy.buffer = NULL;
 	pixman_region32_init(&copy.damage);
 	copy.gamma_lut = NULL;
 	copy.gamma_lut_size = 0;
+	copy.wait_timeline = NULL;
+	copy.signal_timeline = NULL;
 
 	if (src->committed & WLR_OUTPUT_STATE_BUFFER) {
 		wlr_output_state_set_buffer(&copy, src->buffer);
@@ -142,6 +165,15 @@ bool wlr_output_state_copy(struct wlr_output_state *dst,
 		}
 	}
 
+	if (src->committed & WLR_OUTPUT_STATE_WAIT_TIMELINE) {
+		wlr_output_state_set_wait_timeline(&copy, src->wait_timeline,
+			src->wait_point);
+	}
+	if (src->committed & WLR_OUTPUT_STATE_SIGNAL_TIMELINE) {
+		wlr_output_state_set_signal_timeline(&copy, src->signal_timeline,
+			src->signal_point);
+	}
+
 	wlr_output_state_finish(dst);
 	*dst = copy;
 	return true;