[PATCH 2/2] compositor-drm: don't create and destroy kms fbs on every frame

[Ander Conselvan de Oliveira]

Use the new gbm_get/set_user_data() to reuse the kms fbs if the gbm
surface's bo's are reused.
---
 src/compositor-drm.c |   94 +++++++++++++++++++++++++++++++++++++++----------
 1 files changed, 75 insertions(+), 19 deletions(-)

diff --git a/src/compositor-drm.c b/src/compositor-drm.c
index e7433f7..e9b556c 100644
--- a/src/compositor-drm.c
+++ b/src/compositor-drm.c
@@ -199,12 +199,51 @@ drm_output_prepare_scanout_surface(struct drm_output *output)
 	return 0;
 }
 
+struct bo_user_data {
+	uint32_t fb_id;
+};
+
+static void
+bo_set_fb_id(struct gbm_bo *bo, uint32_t fb_id)
+{
+	struct bo_user_data *user_data= gbm_bo_get_user_data(bo);
+
+	if (!user_data)
+		return;
+
+	user_data->fb_id = fb_id;
+}
+
+static uint32_t
+bo_get_fb_id(struct gbm_bo *bo)
+{
+	struct bo_user_data *user_data= gbm_bo_get_user_data(bo);
+
+	if (user_data)
+		return user_data->fb_id;
+	else
+		return 0;
+}
+
+static void
+bo_free_user_data(struct gbm_bo *bo, void *data)
+{
+	struct gbm_device *gbm = gbm_bo_get_device(bo);
+	struct bo_user_data *user_data = data;
+
+	if (user_data->fb_id)
+		drmModeRmFB(gbm_device_get_fd(gbm), user_data->fb_id);
+
+	free(data);
+}
+
 static void
 drm_output_render(struct drm_output *output, pixman_region32_t *damage)
 {
 	struct drm_compositor *compositor =
 		(struct drm_compositor *) output->base.compositor;
 	struct weston_surface *surface;
+	struct bo_user_data *data;
 
 	if (!eglMakeCurrent(compositor->base.display, output->egl_surface,
 			    output->egl_surface, compositor->base.context)) {
@@ -223,6 +262,15 @@ drm_output_render(struct drm_output *output, pixman_region32_t *damage)
 		fprintf(stderr, "failed to lock front buffer: %m\n");
 		return;
 	}
+
+	data = calloc(1, sizeof *data);
+	if (!data) {
+		gbm_surface_release_buffer(output->surface, output->next_bo);
+		output->next_bo = NULL;
+		return;
+	}
+
+	gbm_bo_set_user_data(output->next_bo, data, bo_free_user_data);
 }
 
 static void
@@ -241,6 +289,8 @@ drm_output_repaint(struct weston_output *output_base,
 	if (!output->next_bo)
 		drm_output_render(output, damage);
 
+	output->next_fb_id = bo_get_fb_id(output->next_bo);
+
 	stride = gbm_bo_get_pitch(output->next_bo);
 	handle = gbm_bo_get_handle(output->next_bo).u32;
 
@@ -252,15 +302,20 @@ drm_output_repaint(struct weston_output *output_base,
 		output->next_bo = NULL;
 	}
 
-	ret = drmModeAddFB(compositor->drm.fd,
-			   output->base.current->width,
-			   output->base.current->height,
-			   24, 32, stride, handle, &output->next_fb_id);
-	if (ret) {
-		fprintf(stderr, "failed to create kms fb: %m\n");
-		gbm_surface_release_buffer(output->surface, output->next_bo);
-		output->next_bo = NULL;
-		return;
+	if (!output->next_fb_id) {
+		ret = drmModeAddFB(compositor->drm.fd,
+				   output->base.current->width,
+				   output->base.current->height,
+				   24, 32, stride, handle, &output->next_fb_id);
+		if (ret) {
+			fprintf(stderr, "failed to create kms fb: %m\n");
+			gbm_surface_release_buffer(output->surface, output->next_bo);
+			output->next_bo = NULL;
+			return;
+		}
+
+		if (output->next_bo)
+			bo_set_fb_id(output->next_bo, output->next_fb_id);
 	}
 
 	mode = container_of(output->base.current, struct drm_mode, base);
@@ -355,22 +410,23 @@ page_flip_handler(int fd, unsigned int frame,
 		(struct drm_compositor *) output->base.compositor;
 	uint32_t msecs;
 
-	if (output->current_fb_id)
-		drmModeRmFB(c->drm.fd, output->current_fb_id);
-	output->current_fb_id = output->next_fb_id;
-	output->next_fb_id = 0;
-
-	if (output->scanout_buffer) {
-		weston_buffer_post_release(output->scanout_buffer);
-		wl_list_remove(&output->scanout_buffer_destroy_listener.link);
-		output->scanout_buffer = NULL;
-	} else if (output->current_bo) {
+	if (output->current_bo) {
 		gbm_surface_release_buffer(output->surface,
 					   output->current_bo);
+	} else {
+		if (output->scanout_buffer) {
+			weston_buffer_post_release(output->scanout_buffer);
+			wl_list_remove(&output->scanout_buffer_destroy_listener.link);
+			output->scanout_buffer = NULL;
+		}
+		if (output->current_fb_id)
+			drmModeRmFB(c->drm.fd, output->current_fb_id);
 	}
 
 	output->current_bo = output->next_bo;
 	output->next_bo = NULL;
+	output->current_fb_id = output->next_fb_id;
+	output->next_fb_id = 0;
 
 	if (output->pending_scanout_buffer) {
 		output->scanout_buffer = output->pending_scanout_buffer;
-- 
1.7.4.1