Add basic support for dynamically loadable plugins

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

plugin.h

@@ -0,0 +1,77 @@
+/* Plugin framework
+ *
+ * Copyright (c) 2012  Joachim Nilsson <troglobit@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef PLUGIN_H_
+#define PLUGIN_H_
+
+#include <sys/queue.h>		/* BSD sys/queue.h API */
+
+#define __unused __attribute__ ((unused))
+#define PLUGIN_INIT(x) void x(void) __attribute__ ((constructor));
+#define PLUGIN_EXIT(x) void x(void) __attribute__ ((destructor));
+
+#define PLUGIN_ITERATOR(x)  LIST_FOREACH(x, &plugins, link)
+
+/*
+ * Predefined hook points for easier plugin debugging 
+ */
+typedef enum {
+	HOOK_POST_LOAD = 0,
+	HOOK_PRE_SETUP,
+	HOOK_PRE_RUNLOOP,
+	HOOK_EXIT_CLEANUP,
+	HOOK_MAX_NUM
+} hook_point_t;
+
+typedef struct plugin {
+	/* BSD sys/queue.h linked list node. */
+	LIST_ENTRY(plugin) link;
+
+	/* Optional plugin name, defaults to plugin path if unset. */
+	const char *name;
+
+	/* Service callback to be called once per lap of runloop. */
+	struct {
+		void *arg;	/* Optional argument to callback func. */
+		void (*cb) (void *);
+	} svc;
+
+	/* List of hook callbacks. */
+	struct {
+		void *arg;     /* Optional argument to callback func. */
+		void (*cb) (void *);
+	} hook[HOOK_MAX_NUM];
+} plugin_t;
+
+/* Public plugin API */
+int plugin_register   (plugin_t *plugin);
+int plugin_unregister (plugin_t *plugin);
+
+/* Private daemon API */
+void run_hooks        (hook_point_t no);
+void run_services     (void);
+int  load_plugins     (void);
+
+#endif	/* PLUGIN_H_ */
+
+/**
+ * Local Variables:
+ *  version-control: t
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */