[PATCH 2/3] compositor-drm: Add option to disable early buffer release

[Ander Conselvan de Oliveira]

From: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira at intel.com>

This together with a follow up patch should make it possible to do a
runtime renderer switch without causing artifact on the screen.
---
 man/weston-drm.man   |    6 ++++++
 src/compositor-drm.c |   27 +++++++++++++++++----------
 src/compositor.c     |    1 +
 3 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/man/weston-drm.man b/man/weston-drm.man
index 35d62ae..d3d0b70 100644
--- a/man/weston-drm.man
+++ b/man/weston-drm.man
@@ -106,6 +106,12 @@ instead of the default seat
 Launch Weston on tty
 .I x
 instead of using the current tty.
+.TP
+.B \-\-disable\-early\-buffer\-release
+Don't release buffers early and instead keep references to them as
+long as any surface uses them, even if the compositor has an
+internal copy of the buffer contents. This causes some clients to
+allocate more memory than necessary.
 .
 .\" ***************************************************************
 .SH ENVIRONMENT
diff --git a/src/compositor-drm.c b/src/compositor-drm.c
index 5cb0fab..a3c769d 100644
--- a/src/compositor-drm.c
+++ b/src/compositor-drm.c
@@ -103,6 +103,7 @@ struct drm_compositor {
 	int cursors_are_broken;
 
 	int use_pixman;
+	int disable_early_release;
 
 	uint32_t prev_state;
 
@@ -199,6 +200,7 @@ struct drm_parameters {
 	int connector;
 	int tty;
 	int use_pixman;
+	int disable_early_release;
 	const char *seat_id;
 };
 
@@ -1056,18 +1058,20 @@ drm_assign_planes(struct weston_output *output)
 	pixman_region32_init(&overlap);
 	primary = &c->base.primary_plane;
 
-	/* Flag all visible surfaces as keep_buffer = 1 */
-	wl_list_for_each(ev, &c->base.view_list, link)
-		ev->surface->keep_buffer = 1;
-
 	wl_list_for_each_safe(ev, next, &c->base.view_list, link) {
-		/* test whether this buffer can ever go into a plane:
-		 * non-shm, or small enough to be a cursor
+		struct weston_surface *es = ev->surface;
+
+		/* Test whether this buffer can ever go into a plane:
+		 * non-shm, or small enough to be a cursor. Also honor
+		 * the --disable-early-buffer-release option.
 		 */
-		if (!ev->surface->buffer_ref.buffer ||
-		    (wl_shm_buffer_get(ev->surface->buffer_ref.buffer->resource) &&
-		    (ev->geometry.width > 64 || ev->geometry.height > 64)))
-			ev->surface->keep_buffer = 0;
+		if (c->disable_early_release ||
+		    (es->buffer_ref.buffer &&
+		    (!wl_shm_buffer_get(es->buffer_ref.buffer->resource) ||
+		     (ev->geometry.width <= 64 && ev->geometry.height <= 64))))
+			es->keep_buffer = 1;
+		else
+			es->keep_buffer = 0;
 
 		pixman_region32_init(&surface_overlap);
 		pixman_region32_intersect(&surface_overlap, &overlap,
@@ -2691,6 +2695,7 @@ drm_compositor_create(struct wl_display *display,
 	free(s);
 
 	ec->use_pixman = param->use_pixman;
+	ec->disable_early_release = param->disable_early_release;
 
 	if (weston_compositor_init(&ec->base, display, argc, argv,
 				   config) < 0) {
@@ -2839,6 +2844,8 @@ backend_init(struct wl_display *display, int *argc, char *argv[],
 		{ WESTON_OPTION_INTEGER, "tty", 0, &param.tty },
 		{ WESTON_OPTION_BOOLEAN, "current-mode", 0, &option_current_mode },
 		{ WESTON_OPTION_BOOLEAN, "use-pixman", 0, &param.use_pixman },
+		{ WESTON_OPTION_BOOLEAN, "disable-early-buffer-release", 0,
+		  &param.disable_early_release }
 	};
 
 	param.seat_id = default_seat;
diff --git a/src/compositor.c b/src/compositor.c
index b8e0c6e..a43e3aa 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -3692,6 +3692,7 @@ usage(int error_code)
 		"  --seat=SEAT\t\tThe seat that weston should run on\n"
 		"  --tty=TTY\t\tThe tty to use\n"
 		"  --use-pixman\t\tUse the pixman (CPU) renderer\n"
+		"  --disable-early-bufffer-release\tDisable early buffer release\n"
 		"  --current-mode\tPrefer current KMS mode over EDID preferred mode\n\n");
 
 	fprintf(stderr,
-- 
1.7.9.5