backend/wayland: add support for explicit sync

wl_buffer.release event delivery becomes undefined when using the
linux-drm-syncobj-v1 protocol, so we need to wait for buffer
release via a timeline point instead.

The protocol requires both wait and signal timelines to be set, so
we need to create one when the compositor only supplies a wait
timeline.

backend/wayland/backend.c

@@ -21,6 +21,7 @@
 
 #include "drm-client-protocol.h"
 #include "linux-dmabuf-v1-client-protocol.h"
+#include "linux-drm-syncobj-v1-client-protocol.h"
 #include "pointer-gestures-unstable-v1-client-protocol.h"
 #include "presentation-time-client-protocol.h"
 #include "xdg-activation-v1-client-protocol.h"
@@ -411,6 +412,9 @@ static void registry_global(void *data, struct wl_registry *registry,
 	} else if (strcmp(iface, wp_viewporter_interface.name) == 0) {
 		wl->viewporter = wl_registry_bind(registry, name,
 			&wp_viewporter_interface, 1);
+	} else if (strcmp(iface, wp_linux_drm_syncobj_manager_v1_interface.name) == 0) {
+		wl->drm_syncobj_manager_v1 = wl_registry_bind(registry, name,
+			&wp_linux_drm_syncobj_manager_v1_interface, 1);
 	}
 }
 
@@ -484,6 +488,11 @@ static void backend_destroy(struct wlr_backend *backend) {
 		destroy_wl_buffer(buffer);
 	}
 
+	struct wlr_wl_drm_syncobj_timeline *timeline, *tmp_timeline;
+	wl_list_for_each_safe(timeline, tmp_timeline, &wl->drm_syncobj_timelines, link) {
+		destroy_wl_drm_syncobj_timeline(timeline);
+	}
+
 	wlr_backend_finish(backend);
 
 	wl_list_remove(&wl->event_loop_destroy.link);
@@ -518,6 +527,9 @@ static void backend_destroy(struct wlr_backend *backend) {
 	if (wl->zwp_linux_dmabuf_v1) {
 		zwp_linux_dmabuf_v1_destroy(wl->zwp_linux_dmabuf_v1);
 	}
+	if (wl->drm_syncobj_manager_v1) {
+		wp_linux_drm_syncobj_manager_v1_destroy(wl->drm_syncobj_manager_v1);
+	}
 	if (wl->legacy_drm != NULL) {
 		wl_drm_destroy(wl->legacy_drm);
 	}
@@ -592,6 +604,7 @@ struct wlr_backend *wlr_wl_backend_create(struct wl_event_loop *loop,
 	wl_list_init(&wl->outputs);
 	wl_list_init(&wl->seats);
 	wl_list_init(&wl->buffers);
+	wl_list_init(&wl->drm_syncobj_timelines);
 
 	if (remote_display != NULL) {
 		wl->remote_display = remote_display;
@@ -624,6 +637,8 @@ struct wlr_backend *wlr_wl_backend_create(struct wl_event_loop *loop,
 		goto error_registry;
 	}
 
+	wl->backend.features.timeline = wl->drm_syncobj_manager_v1 != NULL;
+
 	wl_display_roundtrip(wl->remote_display); // process initial event bursts
 
 	struct zwp_linux_dmabuf_feedback_v1 *linux_dmabuf_feedback_v1 = NULL;

backend/wayland/meson.build

@@ -15,6 +15,7 @@ wlr_files += files(
 client_protos = [
 	'drm',
 	'linux-dmabuf-v1',
+	'linux-drm-syncobj-v1',
 	'pointer-gestures-unstable-v1',
 	'presentation-time',
 	'relative-pointer-unstable-v1',

backend/wayland/output.c

@@ -11,6 +11,7 @@
 #include <wayland-client-protocol.h>
 
 #include <wlr/interfaces/wlr_output.h>
+#include <wlr/render/drm_syncobj.h>
 #include <wlr/render/wlr_renderer.h>
 #include <wlr/types/wlr_output_layer.h>
 #include <wlr/util/log.h>
@@ -20,6 +21,7 @@
 #include "types/wlr_output.h"
 
 #include "linux-dmabuf-v1-client-protocol.h"
+#include "linux-drm-syncobj-v1-client-protocol.h"
 #include "presentation-time-client-protocol.h"
 #include "viewporter-client-protocol.h"
 #include "xdg-activation-v1-client-protocol.h"
@@ -31,7 +33,9 @@ static const uint32_t SUPPORTED_OUTPUT_STATE =
 	WLR_OUTPUT_STATE_BUFFER |
 	WLR_OUTPUT_STATE_ENABLED |
 	WLR_OUTPUT_STATE_MODE |
-	WLR_OUTPUT_STATE_ADAPTIVE_SYNC_ENABLED;
+	WLR_OUTPUT_STATE_ADAPTIVE_SYNC_ENABLED |
+	WLR_OUTPUT_STATE_WAIT_TIMELINE |
+	WLR_OUTPUT_STATE_SIGNAL_TIMELINE;
 
 static size_t last_output_num = 0;
 
@@ -140,19 +144,40 @@ void destroy_wl_buffer(struct wlr_wl_buffer *buffer) {
 	if (!buffer->released) {
 		wlr_buffer_unlock(buffer->buffer);
 	}
+	wlr_drm_syncobj_timeline_unref(buffer->fallback_signal_timeline);
 	free(buffer);
 }
 
+static void buffer_release(struct wlr_wl_buffer *buffer) {
+	if (buffer->released) {
+		return;
+	}
+	buffer->released = true;
+	wlr_buffer_unlock(buffer->buffer); // might free buffer
+}
+
 static void buffer_handle_release(void *data, struct wl_buffer *wl_buffer) {
 	struct wlr_wl_buffer *buffer = data;
-	buffer->released = true;
-	wlr_buffer_unlock(buffer->buffer); // might free buffer
+	if (buffer->has_drm_syncobj_waiter) {
+		return;
+	}
+	buffer_release(buffer);
 }
 
 static const struct wl_buffer_listener buffer_listener = {
 	.release = buffer_handle_release,
 };
 
+static void buffer_handle_drm_syncobj_ready(struct wl_listener *listener, void *data) {
+	struct wlr_wl_buffer *buffer = wl_container_of(listener, buffer, drm_syncobj_ready);
+
+	wl_list_remove(&buffer->drm_syncobj_ready.link);
+	wlr_drm_syncobj_timeline_waiter_finish(&buffer->drm_syncobj_waiter);
+	buffer->has_drm_syncobj_waiter = false;
+
+	buffer_release(buffer);
+}
+
 static void buffer_handle_buffer_destroy(struct wl_listener *listener,
 		void *data) {
 	struct wlr_wl_buffer *buffer =
@@ -293,6 +318,58 @@ static struct wlr_wl_buffer *get_or_create_wl_buffer(struct wlr_wl_backend *wl,
 	return create_wl_buffer(wl, wlr_buffer);
 }
 
+void destroy_wl_drm_syncobj_timeline(struct wlr_wl_drm_syncobj_timeline *timeline) {
+	wp_linux_drm_syncobj_timeline_v1_destroy(timeline->wl);
+	wlr_addon_finish(&timeline->addon);
+	wl_list_remove(&timeline->link);
+	free(timeline);
+}
+
+static void drm_syncobj_timeline_addon_destroy(struct wlr_addon *addon) {
+	struct wlr_wl_drm_syncobj_timeline *timeline = wl_container_of(addon, timeline, addon);
+	destroy_wl_drm_syncobj_timeline(timeline);
+}
+
+static const struct wlr_addon_interface drm_syncobj_timeline_addon_impl = {
+	.name = "wlr_wl_drm_syncobj_timeline",
+	.destroy = drm_syncobj_timeline_addon_destroy,
+};
+
+static struct wlr_wl_drm_syncobj_timeline *get_or_create_drm_syncobj_timeline(
+		struct wlr_wl_backend *wl, struct wlr_drm_syncobj_timeline *wlr_timeline) {
+	struct wlr_addon *addon =
+		wlr_addon_find(&wlr_timeline->addons, wl, &drm_syncobj_timeline_addon_impl);
+	if (addon != NULL) {
+		struct wlr_wl_drm_syncobj_timeline *timeline = wl_container_of(addon, timeline, addon);
+		return timeline;
+	}
+
+	struct wlr_wl_drm_syncobj_timeline *timeline = calloc(1, sizeof(*timeline));
+	if (timeline == NULL) {
+		return NULL;
+	}
+
+	timeline->base = wlr_timeline;
+
+	int fd = wlr_drm_syncobj_timeline_export(wlr_timeline);
+	if (fd < 0) {
+		free(timeline);
+		return NULL;
+	}
+
+	timeline->wl = wp_linux_drm_syncobj_manager_v1_import_timeline(wl->drm_syncobj_manager_v1, fd);
+	close(fd);
+	if (timeline->wl == NULL) {
+		free(timeline);
+		return NULL;
+	}
+
+	wlr_addon_init(&timeline->addon, &wlr_timeline->addons, wl, &drm_syncobj_timeline_addon_impl);
+	wl_list_insert(&wl->drm_syncobj_timelines, &timeline->link);
+
+	return timeline;
+}
+
 static bool update_title(struct wlr_wl_output *output, const char *title) {
 	struct wlr_output *wlr_output = &output->wlr_output;
 
@@ -387,6 +464,21 @@ static bool output_test(struct wlr_output *wlr_output,
 		return false;
 	}
 
+	if ((state->committed & WLR_OUTPUT_STATE_SIGNAL_TIMELINE) &&
+			!(state->committed & WLR_OUTPUT_STATE_WAIT_TIMELINE)) {
+		wlr_log(WLR_DEBUG, "Signal timeline requires a wait timeline");
+		return false;
+	}
+
+	if ((state->committed & WLR_OUTPUT_STATE_WAIT_TIMELINE) ||
+			(state->committed & WLR_OUTPUT_STATE_SIGNAL_TIMELINE)) {
+		struct wlr_dmabuf_attributes dmabuf;
+		if (!wlr_buffer_get_dmabuf(state->buffer, &dmabuf)) {
+			wlr_log(WLR_DEBUG, "Wait/signal timelines require DMA-BUFs");
+			return false;
+		}
+	}
+
 	if (state->committed & WLR_OUTPUT_STATE_LAYERS) {
 		// If we can't use a sub-surface for a layer, then we can't use a
 		// sub-surface for any layer underneath
@@ -660,6 +752,7 @@ static bool output_commit(struct wlr_output *wlr_output,
 		}
 	}
 
+	struct wlr_wl_buffer *buffer = NULL;
 	if (state->committed & WLR_OUTPUT_STATE_BUFFER) {
 		const pixman_region32_t *damage = NULL;
 		if (state->committed & WLR_OUTPUT_STATE_DAMAGE) {
@@ -667,8 +760,7 @@ static bool output_commit(struct wlr_output *wlr_output,
 		}
 
 		struct wlr_buffer *wlr_buffer = state->buffer;
-		struct wlr_wl_buffer *buffer =
-			get_or_create_wl_buffer(output->backend, wlr_buffer);
+		buffer = get_or_create_wl_buffer(output->backend, wlr_buffer);
 		if (buffer == NULL) {
 			return false;
 		}
@@ -677,6 +769,66 @@ static bool output_commit(struct wlr_output *wlr_output,
 		damage_surface(output->surface, damage);
 	}
 
+	if (state->committed & WLR_OUTPUT_STATE_WAIT_TIMELINE) {
+		struct wlr_wl_drm_syncobj_timeline *wait_timeline =
+			get_or_create_drm_syncobj_timeline(output->backend, state->wait_timeline);
+
+		struct wlr_wl_drm_syncobj_timeline *signal_timeline;
+		uint64_t signal_point;
+		if (state->committed & WLR_OUTPUT_STATE_SIGNAL_TIMELINE) {
+			signal_timeline = get_or_create_drm_syncobj_timeline(output->backend, state->signal_timeline);
+			signal_point = state->signal_point;
+		} else {
+			if (buffer->fallback_signal_timeline == NULL) {
+				buffer->fallback_signal_timeline =
+					wlr_drm_syncobj_timeline_create(output->backend->drm_fd);
+				if (buffer->fallback_signal_timeline == NULL) {
+					return false;
+				}
+			}
+			signal_timeline =
+				get_or_create_drm_syncobj_timeline(output->backend, buffer->fallback_signal_timeline);
+			signal_point = ++buffer->fallback_signal_point;
+		}
+
+		if (wait_timeline == NULL || signal_timeline == NULL) {
+			return false;
+		}
+
+		if (output->drm_syncobj_surface_v1 == NULL) {
+			output->drm_syncobj_surface_v1 = wp_linux_drm_syncobj_manager_v1_get_surface(
+				output->backend->drm_syncobj_manager_v1, output->surface);
+			if (output->drm_syncobj_surface_v1 == NULL) {
+				return false;
+			}
+		}
+
+		uint32_t wait_point_hi = state->wait_point >> 32;
+		uint32_t wait_point_lo = state->wait_point & UINT32_MAX;
+		uint32_t signal_point_hi = signal_point >> 32;
+		uint32_t signal_point_lo = signal_point & UINT32_MAX;
+
+		wp_linux_drm_syncobj_surface_v1_set_acquire_point(output->drm_syncobj_surface_v1,
+			wait_timeline->wl, wait_point_hi, wait_point_lo);
+		wp_linux_drm_syncobj_surface_v1_set_release_point(output->drm_syncobj_surface_v1,
+			signal_timeline->wl, signal_point_hi, signal_point_lo);
+
+		if (!wlr_drm_syncobj_timeline_waiter_init(&buffer->drm_syncobj_waiter,
+				signal_timeline->base, signal_point, 0, output->backend->event_loop)) {
+			return false;
+		}
+		buffer->has_drm_syncobj_waiter = true;
+
+		buffer->drm_syncobj_ready.notify = buffer_handle_drm_syncobj_ready;
+		wl_signal_add(&buffer->drm_syncobj_waiter.events.ready,
+			&buffer->drm_syncobj_ready);
+	} else {
+		if (output->drm_syncobj_surface_v1 != NULL) {
+			wp_linux_drm_syncobj_surface_v1_destroy(output->drm_syncobj_surface_v1);
+			output->drm_syncobj_surface_v1 = NULL;
+		}
+	}
+
 	if ((state->committed & WLR_OUTPUT_STATE_LAYERS) &&
 			!commit_layers(output, state->layers, state->layers_len)) {
 		return false;
@@ -801,6 +953,9 @@ static void output_destroy(struct wlr_output *wlr_output) {
 		wl_callback_destroy(output->unmap_callback);
 	}
 
+	if (output->drm_syncobj_surface_v1) {
+		wp_linux_drm_syncobj_surface_v1_destroy(output->drm_syncobj_surface_v1);
+	}
 	if (output->zxdg_toplevel_decoration_v1) {
 		zxdg_toplevel_decoration_v1_destroy(output->zxdg_toplevel_decoration_v1);
 	}

include/backend/wayland.h

@@ -14,6 +14,7 @@
 #include <wlr/types/wlr_tablet_tool.h>
 #include <wlr/types/wlr_touch.h>
 #include <wlr/render/drm_format_set.h>
+#include <wlr/render/drm_syncobj.h>
 
 struct wlr_wl_backend {
 	struct wlr_backend backend;
@@ -40,6 +41,8 @@ struct wlr_wl_backend {
 	struct wp_presentation *presentation;
 	struct wl_shm *shm;
 	struct zwp_linux_dmabuf_v1 *zwp_linux_dmabuf_v1;
+	struct wp_linux_drm_syncobj_manager_v1 *drm_syncobj_manager_v1;
+	struct wl_list drm_syncobj_timelines; // wlr_wl_drm_syncobj_timeline.link
 	struct zwp_relative_pointer_manager_v1 *zwp_relative_pointer_manager_v1;
 	struct wl_list seats; // wlr_wl_seat.link
 	struct zwp_tablet_manager_v2 *tablet_manager;
@@ -58,6 +61,20 @@ struct wlr_wl_buffer {
 	bool released;
 	struct wl_list link; // wlr_wl_backend.buffers
 	struct wl_listener buffer_destroy;
+
+	bool has_drm_syncobj_waiter;
+	struct wlr_drm_syncobj_timeline_waiter drm_syncobj_waiter;
+	struct wl_listener drm_syncobj_ready;
+
+	struct wlr_drm_syncobj_timeline *fallback_signal_timeline;
+	uint64_t fallback_signal_point;
+};
+
+struct wlr_wl_drm_syncobj_timeline {
+	struct wlr_drm_syncobj_timeline *base;
+	struct wlr_addon addon;
+	struct wl_list link; // wlr_wl_backend.drm_syncobj_timelines
+	struct wp_linux_drm_syncobj_timeline_v1 *wl;
 };
 
 struct wlr_wl_presentation_feedback {
@@ -88,6 +105,7 @@ struct wlr_wl_output {
 	struct xdg_surface *xdg_surface;
 	struct xdg_toplevel *xdg_toplevel;
 	struct zxdg_toplevel_decoration_v1 *zxdg_toplevel_decoration_v1;
+	struct wp_linux_drm_syncobj_surface_v1 *drm_syncobj_surface_v1;
 	struct wl_list presentation_feedbacks;
 
 	char *title;
@@ -190,6 +208,7 @@ bool create_wl_seat(struct wl_seat *wl_seat, struct wlr_wl_backend *wl,
 	uint32_t global_name);
 void destroy_wl_seat(struct wlr_wl_seat *seat);
 void destroy_wl_buffer(struct wlr_wl_buffer *buffer);
+void destroy_wl_drm_syncobj_timeline(struct wlr_wl_drm_syncobj_timeline *timeline);
 
 extern const struct wlr_pointer_impl wl_pointer_impl;
 extern const struct wlr_tablet_pad_impl wl_tablet_pad_impl;