libweston, backends: store backend pointer in struct weston_head

Compositor code can use opaque pointer comparison to determine whether
a head belongs to a given backend. Store a backend pointer in struct
weston_head to enable the compositor to select the correct backend
specific output configuration code.

This also allows to use the backend pointer instead of the opaque
backend_id pointer to check whether a head belongs to a backend, so
replace the checks in all to_xyz_head() functions and drop backend_id.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

include/libweston/libweston.h

@@ -375,6 +375,7 @@ struct weston_color_characteristics {
  */
 struct weston_head {
 	struct weston_compositor *compositor;	/**< owning compositor */
+	struct weston_backend *backend;	/**< owning backend */
 	struct wl_list compositor_link;	/**< in weston_compositor::head_list */
 	struct wl_signal destroy_signal;	/**< destroy callbacks */
 
@@ -406,9 +407,6 @@ struct weston_head {
 
 	/** Current content protection status */
 	enum weston_hdcp_protection current_protection;
-
-	/** Opaque pointer used by backends to identify heads as theirs */
-	const void *backend_id;
 };
 
 /** Output properties derived from its color characteristics and profile

libweston/backend-drm/drm-internal.h

@@ -601,12 +601,12 @@ struct drm_output {
 };
 
 void
-drm_head_destroy(struct weston_head *head_base);
+drm_destroy(struct weston_compositor *ec);
 
 static inline struct drm_head *
 to_drm_head(struct weston_head *base)
 {
-	if (base->backend_id != drm_head_destroy)
+	if (base->backend->destroy != drm_destroy)
 		return NULL;
 	return container_of(base, struct drm_head, base);
 }

libweston/backend-drm/drm.c

@@ -2272,7 +2272,7 @@ drm_head_create(struct drm_device *device, drmModeConnector *conn,
 	weston_head_init(&head->base, name);
 	free(name);
 
-	head->base.backend_id = drm_head_destroy;
+	head->base.backend = &backend->base;
 
 	ret = drm_head_update_info(head, conn);
 	if (ret < 0)
@@ -2303,7 +2303,7 @@ err:
 	return -1;
 }
 
-void
+static void
 drm_head_destroy(struct weston_head *base)
 {
 	struct drm_head *head = to_drm_head(base);
@@ -2692,7 +2692,7 @@ udev_drm_event(int fd, uint32_t mask, void *data)
 	return 1;
 }
 
-static void
+void
 drm_destroy(struct weston_compositor *ec)
 {
 	struct drm_backend *b = to_drm_backend(ec);

libweston/backend-headless/headless.c

@@ -88,12 +88,12 @@ static const uint32_t headless_formats[] = {
 };
 
 static void
-headless_head_destroy(struct weston_head *base);
+headless_destroy(struct weston_compositor *ec);
 
 static inline struct headless_head *
 to_headless_head(struct weston_head *base)
 {
-	if (base->backend_id != headless_head_destroy)
+	if (base->backend->destroy != headless_destroy)
 		return NULL;
 	return container_of(base, struct headless_head, base);
 }
@@ -505,6 +505,7 @@ static int
 headless_head_create(struct weston_compositor *compositor,
 		     const char *name)
 {
+	struct headless_backend *backend = to_headless_backend(compositor);
 	struct headless_head *head;
 
 	/* name can't be NULL. */
@@ -516,7 +517,7 @@ headless_head_create(struct weston_compositor *compositor,
 
 	weston_head_init(&head->base, name);
 
-	head->base.backend_id = headless_head_destroy;
+	head->base.backend = &backend->base;
 
 	weston_head_set_connection_status(&head->base, true);
 	weston_head_set_supported_eotf_mask(&head->base,

libweston/backend-rdp/rdp.c

@@ -534,6 +534,7 @@ rdp_output_create(struct weston_compositor *compositor, const char *name)
 static int
 rdp_head_create(struct weston_compositor *compositor, const char *name)
 {
+	struct rdp_backend *backend = to_rdp_backend(compositor);
 	struct rdp_head *head;
 
 	head = zalloc(sizeof *head);
@@ -542,7 +543,7 @@ rdp_head_create(struct weston_compositor *compositor, const char *name)
 
 	weston_head_init(&head->base, name);
 
-	head->base.backend_id = rdp_head_destroy;
+	head->base.backend = &backend->base;
 
 	weston_head_set_connection_status(&head->base, true);
 	weston_compositor_add_head(compositor, &head->base);
@@ -550,7 +551,7 @@ rdp_head_create(struct weston_compositor *compositor, const char *name)
 	return 0;
 }
 
-void
+static void
 rdp_head_destroy(struct weston_head *base)
 {
 	struct rdp_head *head = to_rdp_head(base);
@@ -561,7 +562,7 @@ rdp_head_destroy(struct weston_head *base)
 	free(head);
 }
 
-static void
+void
 rdp_destroy(struct weston_compositor *ec)
 {
 	struct rdp_backend *b = to_rdp_backend(ec);

libweston/backend-rdp/rdp.h

@@ -233,12 +233,12 @@ void
 rdp_clipboard_destroy(RdpPeerContext *peerCtx);
 
 void
-rdp_head_destroy(struct weston_head *base);
+rdp_destroy(struct weston_compositor *ec);
 
 static inline struct rdp_head *
 to_rdp_head(struct weston_head *base)
 {
-	if (base->backend_id != rdp_head_destroy)
+	if (base->backend->destroy != rdp_destroy)
 		return NULL;
 	return container_of(base, struct rdp_head, base);
 }

libweston/backend-vnc/vnc.c

@@ -122,10 +122,13 @@ to_vnc_output(struct weston_output *base)
 static void
 vnc_head_destroy(struct weston_head *base);
 
+static void
+vnc_destroy(struct weston_compositor *ec);
+
 static inline struct vnc_head *
 to_vnc_head(struct weston_head *base)
 {
-	if (base->backend_id != vnc_head_destroy)
+	if (base->backend->destroy != vnc_destroy)
 		return NULL;
 	return container_of(base, struct vnc_head, base);
 }
@@ -723,6 +726,7 @@ vnc_destroy(struct weston_compositor *ec)
 static void
 vnc_head_create(struct weston_compositor *compositor, const char *name)
 {
+	struct vnc_backend *backend = to_vnc_backend(compositor);
 	struct vnc_head *head;
 
 	head = xzalloc(sizeof *head);
@@ -731,7 +735,7 @@ vnc_head_create(struct weston_compositor *compositor, const char *name)
 	weston_head_set_monitor_strings(&head->base, "weston", "vnc", NULL);
 	weston_head_set_physical_size(&head->base, 0, 0);
 
-	head->base.backend_id = vnc_head_destroy;
+	head->base.backend = &backend->base;
 
 	weston_head_set_connection_status(&head->base, true);
 	weston_compositor_add_head(compositor, &head->base);

libweston/backend-wayland/wayland.c

@@ -231,12 +231,12 @@ struct wayland_input {
 struct gl_renderer_interface *gl_renderer;
 
 static void
-wayland_head_destroy(struct weston_head *base);
+wayland_destroy(struct weston_compositor *ec);
 
 static inline struct wayland_head *
 to_wayland_head(struct weston_head *base)
 {
-	if (base->backend_id != wayland_head_destroy)
+	if (base->backend->destroy != wayland_destroy)
 		return NULL;
 	return container_of(base, struct wayland_head, base);
 }
@@ -1417,6 +1417,7 @@ wayland_output_create(struct weston_compositor *compositor, const char *name)
 static struct wayland_head *
 wayland_head_create(struct weston_compositor *compositor, const char *name)
 {
+	struct wayland_backend *backend = to_wayland_backend(compositor);
 	struct wayland_head *head;
 
 	assert(name);
@@ -1427,7 +1428,7 @@ wayland_head_create(struct weston_compositor *compositor, const char *name)
 
 	weston_head_init(&head->base, name);
 
-	head->base.backend_id = wayland_head_destroy;
+	head->base.backend = &backend->base;
 
 	weston_head_set_connection_status(&head->base, true);
 	weston_compositor_add_head(compositor, &head->base);

libweston/backend-x11/x11.c

@@ -152,12 +152,12 @@ struct window_delete_data {
 struct gl_renderer_interface *gl_renderer;
 
 static void
-x11_head_destroy(struct weston_head *base);
+x11_destroy(struct weston_compositor *ec);
 
 static inline struct x11_head *
 to_x11_head(struct weston_head *base)
 {
-	if (base->backend_id != x11_head_destroy)
+	if (base->backend->destroy != x11_destroy)
 		return NULL;
 	return container_of(base, struct x11_head, base);
 }
@@ -1175,6 +1175,7 @@ x11_output_create(struct weston_compositor *compositor, const char *name)
 static int
 x11_head_create(struct weston_compositor *compositor, const char *name)
 {
+	struct x11_backend *backend = to_x11_backend(compositor);
 	struct x11_head *head;
 
 	assert(name);
@@ -1185,7 +1186,7 @@ x11_head_create(struct weston_compositor *compositor, const char *name)
 
 	weston_head_init(&head->base, name);
 
-	head->base.backend_id = x11_head_destroy;
+	head->base.backend = &backend->base;
 
 	weston_head_set_connection_status(&head->base, true);
 	weston_compositor_add_head(compositor, &head->base);