renderer: keep patch_lock around and clear current_patch when stopped

This commit makes renderer_lock_patch, renderer_unlock_patch, and
renderer_get_patch produce meaningful resuls also when the renderer
is not running.

src/main.c

@@ -52,6 +52,7 @@
 #include "yaffs.h"
 #include "version.h"
 #include "renderer/videoinreconf.h"
+#include "renderer/renderer.h"
 #include "shellext.h"
 #include "sysconfig.h"
 #include "fb.h"
@@ -95,6 +96,7 @@ static rtems_task gui_task(rtems_task_argument argument)
 	init_osc();
 	init_messagebox();
 	init_performance();
+	init_renderer();
 	init_cp();
 	init_keyboard();
 	init_ir();

src/renderer/renderer.c

@@ -144,7 +144,7 @@ struct patch *renderer_get_patch(int spin)
 	return current_patch;
 }
 
-void renderer_start(int framebuffer_fd, struct patch *p)
+void init_renderer(void)
 {
 	rtems_status_code sc;
 
@@ -156,7 +156,10 @@ void renderer_start(int framebuffer_fd, struct patch *p)
 		&patch_lock
 	);
 	assert(sc == RTEMS_SUCCESSFUL);
+}
 
+void renderer_start(int framebuffer_fd, struct patch *p)
+{
 	assert(mashup_head == NULL);
 	mashup_head = patch_copy(p);
 	current_patch = mashup_head;
@@ -189,5 +192,5 @@ void renderer_stop(void)
 		patch_free(mashup_head);
 		mashup_head = p;
 	}
-	rtems_semaphore_delete(patch_lock);
+	current_patch = NULL;
 }

src/renderer/renderer.h

@@ -42,6 +42,7 @@ void renderer_add_patch(struct patch *p);
 void renderer_del_patch(struct patch *p);
 struct patch *renderer_get_patch(int spin);
 
+void init_renderer(void);
 void renderer_start(int framebuffer_fd, struct patch *p);
 void renderer_stop(void);