output: fix attach_buffer semantics

backend/drm/drm.c

@@ -301,11 +301,44 @@ static bool drm_connector_commit(struct wlr_output *output) {
 		damage = &output->pending.damage;
 	}
 
-	struct gbm_bo *bo = swap_drm_surface_buffers(&plane->surf, damage);
+	struct gbm_bo *bo;
+	uint32_t fb_id = 0;
+	assert(output->pending.committed & WLR_OUTPUT_STATE_BUFFER);
+	switch (output->pending.buffer_type) {
+	case WLR_OUTPUT_STATE_BUFFER_RENDER:
+		bo = swap_drm_surface_buffers(&plane->surf, damage);
+		if (bo == NULL) {
+			wlr_log(WLR_ERROR, "swap_drm_surface_buffers failed");
+			return false;
+		}
+
 		if (drm->parent) {
 			bo = copy_drm_surface_mgpu(&plane->mgpu_surf, bo);
+			if (bo == NULL) {
+				wlr_log(WLR_ERROR, "copy_drm_surface_mgpu failed");
+				return false;
+			}
+		}
+		fb_id = get_fb_for_bo(bo, plane->drm_format);
+		if (fb_id == 0) {
+			wlr_log(WLR_ERROR, "get_fb_for_bo failed");
+			return false;
+		}
+		break;
+	case WLR_OUTPUT_STATE_BUFFER_SCANOUT:
+		bo = import_gbm_bo(&drm->renderer, &conn->pending_dmabuf);
+		if (bo == NULL) {
+			wlr_log(WLR_ERROR, "import_gbm_bo failed");
+			return false;
+		}
+
+		fb_id = get_fb_for_bo(bo, gbm_bo_get_format(bo));
+		if (fb_id == 0) {
+			wlr_log(WLR_ERROR, "get_fb_for_bo failed");
+			return false;
+		}
+		break;
 	}
-	uint32_t fb_id = get_fb_for_bo(bo, plane->drm_format);
 
 	if (conn->pageflip_pending) {
 		wlr_log(WLR_ERROR, "Skipping pageflip on output '%s'", conn->output.name);
@@ -903,30 +936,7 @@ static bool drm_connector_attach_buffer(struct wlr_output *output,
 		}
 	}
 
-	struct gbm_bo *bo = import_gbm_bo(&drm->renderer, &attribs);
-	if (bo == NULL) {
-		wlr_log(WLR_ERROR, "import_gbm_bo failed");
-		return NULL;
-	}
-
-	uint32_t fb_id = get_fb_for_bo(bo, gbm_bo_get_format(bo));
-	if (fb_id == 0) {
-		wlr_log(WLR_ERROR, "get_fb_for_bo failed");
-		return false;
-	}
-
-	if (conn->pageflip_pending) {
-		wlr_log(WLR_ERROR, "Skipping pageflip on output '%s'", conn->output.name);
-		return false;
-	}
-
-	if (!drm->iface->crtc_pageflip(drm, conn, crtc, fb_id, NULL)) {
-		wlr_log(WLR_ERROR, "crtc_pageflip failed");
-		return false;
-	}
-
-	conn->pageflip_pending = true;
-	wlr_output_update_enabled(output, true);
+	memcpy(&conn->pending_dmabuf, &attribs, sizeof(attribs));
 	return true;
 }
 

include/backend/drm/drm.h

@@ -148,6 +148,8 @@ struct wlr_drm_connector {
 	bool pageflip_pending;
 	struct wl_event_source *retry_pageflip;
 	struct wl_list link;
+
+	struct wlr_dmabuf_attributes pending_dmabuf;
 };
 
 struct wlr_drm_backend *get_drm_backend_from_backend(

include/wlr/types/wlr_output.h

@@ -52,12 +52,21 @@ enum wlr_output_state_field {
 	WLR_OUTPUT_STATE_DAMAGE = 1 << 1,
 };
 
+enum wlr_output_state_buffer_type {
+	WLR_OUTPUT_STATE_BUFFER_RENDER,
+	WLR_OUTPUT_STATE_BUFFER_SCANOUT,
+};
+
 /**
  * Holds the double-buffered output state.
  */
 struct wlr_output_state {
 	uint32_t committed; // enum wlr_output_state_field
 	pixman_region32_t damage; // output-buffer-local coordinates
+
+	// only valid if WLR_OUTPUT_STATE_BUFFER
+	enum wlr_output_state_buffer_type buffer_type;
+	struct wlr_buffer *buffer; // if WLR_OUTPUT_STATE_BUFFER_SCANOUT
 };
 
 struct wlr_output_impl;

types/wlr_output.c

@@ -404,6 +404,7 @@ bool wlr_output_attach_render(struct wlr_output *output, int *buffer_age) {
 	}
 
 	output->pending.committed |= WLR_OUTPUT_STATE_BUFFER;
+	output->pending.buffer_type = WLR_OUTPUT_STATE_BUFFER_RENDER;
 	return true;
 }
 
@@ -480,15 +481,6 @@ bool wlr_output_commit(struct wlr_output *output) {
 
 bool wlr_output_attach_buffer(struct wlr_output *output,
 		struct wlr_buffer *buffer) {
-	if (output->frame_pending) {
-		wlr_log(WLR_ERROR, "Tried to swap buffers when a frame is pending");
-		return false;
-	}
-	if (output->idle_frame != NULL) {
-		wl_event_source_remove(output->idle_frame);
-		output->idle_frame = NULL;
-	}
-
 	if (!output->impl->attach_buffer) {
 		return false;
 	}
@@ -496,9 +488,8 @@ bool wlr_output_attach_buffer(struct wlr_output *output,
 		return false;
 	}
 
-	output->frame_pending = true;
-	output->needs_frame = false;
-	pixman_region32_clear(&output->damage);
+	output->pending.committed |= WLR_OUTPUT_STATE_BUFFER;
+	output->pending.buffer_type = WLR_OUTPUT_STATE_BUFFER_SCANOUT;
 	return true;
 }