backend/drm: implement the output layer API

Delegate all of the work to libliftoff.

backend/drm/drm.c

@@ -424,6 +424,11 @@ static bool drm_crtc_commit(struct wlr_drm_connector *conn,
 		if (crtc->cursor != NULL) {
 			drm_fb_move(&crtc->cursor->queued_fb, &crtc->cursor->pending_fb);
 		}
+
+		struct wlr_drm_layer *layer;
+		wl_list_for_each(layer, &state->base->layers, base.pending.link) {
+			drm_fb_move(&layer->queued_fb, &layer->pending_fb);
+		}
 	} else {
 		drm_fb_clear(&crtc->primary->pending_fb);
 		// The set_cursor() hook is a bit special: it's not really synchronized
@@ -432,6 +437,11 @@ static bool drm_crtc_commit(struct wlr_drm_connector *conn,
 		// risk ending up in a state where we don't have a cursor FB but
 		// wlr_drm_connector.cursor_enabled is true.
 		// TODO: fix our output interface to avoid this issue.
+
+		struct wlr_drm_layer *layer;
+		wl_list_for_each(layer, &state->base->layers, base.pending.link) {
+			drm_fb_clear(&layer->pending_fb);
+		}
 	}
 	return ok;
 }
@@ -543,6 +553,23 @@ static bool drm_connector_set_pending_fb(struct wlr_drm_connector *conn,
 	return true;
 }
 
+static void drm_connector_set_pending_layer_fbs(struct wlr_drm_connector *conn,
+		const struct wlr_output_state *state) {
+	struct wlr_drm_backend *drm = conn->backend;
+
+	struct wlr_drm_layer *layer;
+	wl_list_for_each(layer, &state->layers, base.pending.link) {
+		if (!(layer->base.pending.committed & WLR_OUTPUT_LAYER_STATE_BUFFER)) {
+			continue;
+		}
+		struct wlr_buffer *buffer = layer->base.pending.buffer;
+		drm_fb_clear(&layer->pending_fb);
+		if (!drm_fb_import(&layer->pending_fb, drm, buffer, NULL)) {
+			wlr_drm_conn_log(conn, WLR_DEBUG, "Failed to import layer buffer");
+		}
+	}
+}
+
 static bool drm_connector_alloc_crtc(struct wlr_drm_connector *conn);
 
 static bool drm_connector_test(struct wlr_output *output) {
@@ -600,6 +627,8 @@ static bool drm_connector_test(struct wlr_output *output) {
 		return true;
 	}
 
+	drm_connector_set_pending_layer_fbs(conn, pending.base);
+
 	if (pending.base->committed & WLR_OUTPUT_STATE_BUFFER) {
 		if (!drm_connector_set_pending_fb(conn, pending.base)) {
 			return false;
@@ -657,6 +686,8 @@ bool drm_connector_commit_state(struct wlr_drm_connector *conn,
 		}
 	}
 
+	drm_connector_set_pending_layer_fbs(conn, pending.base);
+
 	if (pending.base->committed & WLR_OUTPUT_STATE_BUFFER) {
 		if (!drm_connector_set_pending_fb(conn, pending.base)) {
 			return false;
@@ -1105,6 +1136,25 @@ static const struct wlr_drm_format_set *drm_connector_get_primary_formats(
 	return &conn->crtc->primary->formats;
 }
 
+static struct wlr_output_layer *drm_connector_create_layer(
+		struct wlr_output *wlr_output) {
+	struct wlr_drm_layer *layer = calloc(1, sizeof(*layer));
+	if (layer == NULL) {
+		return NULL;
+	}
+	wlr_output_layer_init(&layer->base, wlr_output);
+	return &layer->base;
+}
+
+static void drm_connector_destroy_layer(struct wlr_output_layer *wlr_layer) {
+	struct wlr_drm_layer *layer = (struct wlr_drm_layer *)wlr_layer;
+	drm_fb_clear(&layer->pending_fb);
+	drm_fb_clear(&layer->queued_fb);
+	drm_fb_clear(&layer->current_fb);
+	liftoff_layer_destroy(layer->liftoff);
+	free(layer);
+}
+
 static const struct wlr_output_impl output_impl = {
 	.set_cursor = drm_connector_set_cursor,
 	.move_cursor = drm_connector_move_cursor,
@@ -1115,6 +1165,8 @@ static const struct wlr_output_impl output_impl = {
 	.get_cursor_formats = drm_connector_get_cursor_formats,
 	.get_cursor_size = drm_connector_get_cursor_size,
 	.get_primary_formats = drm_connector_get_primary_formats,
+	.create_layer = drm_connector_create_layer,
+	.destroy_layer = drm_connector_destroy_layer,
 };
 
 bool wlr_output_is_drm(struct wlr_output *output) {
@@ -1572,6 +1624,11 @@ static void handle_page_flip(int fd, unsigned seq,
 			&conn->crtc->cursor->queued_fb);
 	}
 
+	struct wlr_drm_layer *layer;
+	wl_list_for_each(layer, &conn->output.layers, base.current.link) {
+		drm_fb_move(&layer->current_fb, &layer->queued_fb);
+	}
+
 	uint32_t present_flags = WLR_OUTPUT_PRESENT_VSYNC |
 		WLR_OUTPUT_PRESENT_HW_CLOCK | WLR_OUTPUT_PRESENT_HW_COMPLETION;
 	/* Don't report ZERO_COPY in multi-gpu situations, because we had to copy

backend/drm/libliftoff.c

@@ -76,6 +76,37 @@ static bool disable_plane(struct wlr_drm_plane *plane) {
 	return liftoff_layer_set_property(plane->liftoff_layer, "FB_ID", 0) == 0;
 }
 
+static bool set_layer_props(struct wlr_drm_layer *layer, uint64_t zpos) {
+	bool ok = liftoff_layer_set_property(layer->liftoff, "zpos", zpos) == 0 &&
+		liftoff_layer_set_property(layer->liftoff, "CRTC_X", layer->base.pending.x) == 0 &&
+		liftoff_layer_set_property(layer->liftoff, "CRTC_Y", layer->base.pending.y) == 0;
+
+	if (layer->base.pending.committed & WLR_OUTPUT_LAYER_STATE_BUFFER) {
+		struct wlr_buffer *buffer = layer->base.pending.buffer;
+		uint64_t width = buffer->width;
+		uint64_t height = buffer->height;
+
+		ok = ok &&
+			liftoff_layer_set_property(layer->liftoff, "SRC_X", 0) == 0 &&
+			liftoff_layer_set_property(layer->liftoff, "SRC_Y", 0) == 0 &&
+			liftoff_layer_set_property(layer->liftoff, "SRC_W", width << 16) == 0 &&
+			liftoff_layer_set_property(layer->liftoff, "SRC_H", height << 16) == 0 &&
+			liftoff_layer_set_property(layer->liftoff, "CRTC_W", width) == 0 &&
+			liftoff_layer_set_property(layer->liftoff, "CRTC_H", height) == 0;
+
+		struct wlr_drm_fb *fb = layer->pending_fb;
+		if (fb == NULL) {
+			// We couldn't import the buffer to KMS. Force the layer to be
+			// composited.
+			liftoff_layer_set_fb_composited(layer->liftoff);
+		} else {
+			ok = ok && liftoff_layer_set_property(layer->liftoff, "FB_ID", fb->id) == 0;
+		}
+	}
+
+	return ok;
+}
+
 static bool liftoff_crtc_commit(struct wlr_drm_connector *conn,
 		const struct wlr_drm_connector_state *state, uint32_t flags,
 		bool test_only) {
@@ -116,17 +147,41 @@ static bool liftoff_crtc_commit(struct wlr_drm_connector *conn,
 		if (crtc->cursor) {
 			if (drm_connector_is_cursor_visible(conn)) {
 				ok = ok && set_plane_props(crtc->cursor,
-					crtc->cursor->liftoff_layer,
-					conn->cursor_x, conn->cursor_y, 1);
+					crtc->cursor->liftoff_layer, conn->cursor_x, conn->cursor_y,
+					wl_list_length(&state->base->layers) + 1);
 			} else {
 				ok = ok && disable_plane(crtc->cursor);
 			}
 		}
+
+		size_t i = 0;
+		struct wlr_drm_layer *layer;
+		wl_list_for_each(layer, &state->base->layers, base.pending.link) {
+			if (layer->liftoff == NULL) {
+				layer->liftoff = liftoff_layer_create(crtc->liftoff);
+				if (layer->liftoff == NULL) {
+					wlr_log(WLR_ERROR, "Failed to create libliftoff layer");
+					continue;
+				}
+			}
+
+			layer->base.accepted = false;
+			ok = ok && set_layer_props(layer, i + 1);
+
+			i++;
+		}
 	} else {
 		ok = ok && disable_plane(crtc->primary);
 		if (crtc->cursor) {
 			ok = ok && disable_plane(crtc->cursor);
 		}
+
+		struct wlr_drm_layer *layer;
+		wl_list_for_each(layer, &state->base->layers, base.pending.link) {
+			if (layer->liftoff != NULL) {
+				liftoff_layer_set_property(layer->liftoff, "FB_ID", 0);
+			}
+		}
 	}
 
 	if (!ok) {
@@ -148,6 +203,13 @@ static bool liftoff_crtc_commit(struct wlr_drm_connector *conn,
 		goto out;
 	}
 
+	struct wlr_drm_layer *layer;
+	wl_list_for_each(layer, &state->base->layers, base.pending.link) {
+		if (layer->liftoff != NULL) {
+			layer->base.accepted = !liftoff_layer_needs_composition(layer->liftoff);
+		}
+	}
+
 	ret = drmModeAtomicCommit(drm->fd, req, flags, drm);
 	if (ret != 0) {
 		wlr_drm_conn_log_errno(conn, test_only ? WLR_DEBUG : WLR_ERROR,

include/backend/drm/drm.h

@@ -11,6 +11,7 @@
 #include <wlr/backend/drm.h>
 #include <wlr/backend/session.h>
 #include <wlr/render/drm_format_set.h>
+#include <wlr/types/wlr_output_layer.h>
 #include <xf86drmMode.h>
 #include "backend/drm/iface.h"
 #include "backend/drm/properties.h"
@@ -38,6 +39,18 @@ struct wlr_drm_plane {
 	struct liftoff_layer *liftoff_layer;
 };
 
+struct wlr_drm_layer {
+	struct wlr_output_layer base;
+	struct liftoff_layer *liftoff;
+
+	/* Buffer to be submitted to the kernel on the next page-flip */
+	struct wlr_drm_fb *pending_fb;
+	/* Buffer submitted to the kernel, will be presented on next vblank */
+	struct wlr_drm_fb *queued_fb;
+	/* Buffer currently displayed on screen */
+	struct wlr_drm_fb *current_fb;
+};
+
 struct wlr_drm_crtc {
 	uint32_t id;