Add monitor interface

Add an interface to monitor devices and helper program
Add v4l2 monitor
Add simple dictionary with key/value pairs

spa/include/spa/monitor.h

@@ -0,0 +1,150 @@
+/* Simple Plugin API
+ * Copyright (C) 2016 Wim Taymans <wim.taymans@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __SPA_MONITOR_H__
+#define __SPA_MONITOR_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct _SpaMonitor SpaMonitor;
+
+#include <spa/defs.h>
+#include <spa/dict.h>
+#include <spa/plugin.h>
+
+typedef enum {
+  SPA_MONITOR_ITEM_FLAG_NONE    = 0,
+} SpaMonitorItemFlags;
+
+/**
+ * SpaMonitorItemState:
+ * @SPA_MONITOR_ITEM_STATE_AVAILABLE: The item is available
+ * @SPA_MONITOR_ITEM_STATE_DISABLED: the item is disabled
+ * @SPA_MONITOR_ITEM_STATE_UNAVAILABLE: the item is unavailable
+ */
+typedef enum {
+  SPA_MONITOR_ITEM_STATE_AVAILABLE,
+  SPA_MONITOR_ITEM_STATE_DISABLED,
+  SPA_MONITOR_ITEM_STATE_UNAVAILABLE,
+} SpaMonitorItemState;
+
+typedef struct {
+  const char              *id;
+  SpaMonitorItemFlags      flags;
+  SpaMonitorItemState      state;
+  const char              *name;
+  const char              *klass;
+  const SpaDict           *info;
+  const SpaHandleFactory  *factory;
+  const void              *config;
+} SpaMonitorItem;
+
+/**
+ * SpaMonitorEventType:
+ * @SPA_MONITOR_EVENT_TYPE_INVALID: invalid event
+ * @SPA_MONITOR_EVENT_TYPE_ADDED: an item was added, data points to #SpaMonitorItem
+ * @SPA_MONITOR_EVENT_TYPE_REMOVED: an item was removed, data points to #SpaMonitorItem
+ * @SPA_MONITOR_EVENT_TYPE_CHANGED: an item was changed, data points to #SpaMonitorItem
+ * @SPA_MONITOR_EVENT_TYPE_ADD_POLL: add fd for polling, data points to #SpaPollItem
+ * @SPA_MONITOR_EVENT_TYPE_UPDATE_POLL: update fd for polling, data points to #SpaPollItem
+ * @SPA_MONITOR_EVENT_TYPE_REMOVE_POLL: remov fd for polling, data points to #SpaPollItem
+ */
+typedef enum {
+  SPA_MONITOR_EVENT_TYPE_INVALID = 0,
+  SPA_MONITOR_EVENT_TYPE_ADDED,
+  SPA_MONITOR_EVENT_TYPE_REMOVED,
+  SPA_MONITOR_EVENT_TYPE_CHANGED,
+  SPA_MONITOR_EVENT_TYPE_ADD_POLL,
+  SPA_MONITOR_EVENT_TYPE_UPDATE_POLL,
+  SPA_MONITOR_EVENT_TYPE_REMOVE_POLL,
+} SpaMonitorEventType;
+
+typedef struct {
+  SpaMonitorEventType  type;
+  void                *data;
+  size_t               size;
+} SpaMonitorEvent;
+
+/**
+ * SpaMonitorCallback:
+ * @node: a #SpaMonitor emiting the event
+ * @event: the event that was emited
+ * @user_data: user data provided when registering the callback
+ *
+ * This will be called when a monitor event is notified
+ * on @monitor.
+ */
+typedef void   (*SpaMonitorEventCallback)  (SpaMonitor      *monitor,
+                                            SpaMonitorEvent *event,
+                                            void            *user_data);
+
+#define SPA_INTERFACE_ID_MONITOR                   2
+#define SPA_INTERFACE_ID_MONITOR_NAME              "Monitor interface"
+#define SPA_INTERFACE_ID_MONITOR_DESCRIPTION       "Device Monitor interface"
+
+/**
+ * SpaMonitor:
+ *
+ * The device monitor interface.
+ */
+struct _SpaMonitor {
+  /* pointer to the handle owning this interface */
+  SpaHandle *handle;
+  /**
+   * SpaMonitor::info
+   *
+   * Extra information about the monitor
+   */
+  const SpaDict * info;
+
+  /* the total size of this monitor. This can be used to expand this
+   * structure in the future */
+  size_t size;
+
+  /**
+   * SpaMonitor::set_event_callback:
+   * @monitor: a #SpaMonitor
+   * @callback: a #SpaMonitorEventCallback
+   * @user_data: extra user data
+   *
+   * Set an event callback to receive asynchronous notifications from
+   * the monitor.
+   *
+   * Returns: #SPA_RESULT_OK on success
+   */
+  SpaResult  (*set_event_callback)   (SpaMonitor              *monitor,
+                                      SpaMonitorEventCallback  callback,
+                                      void                    *user_data);
+
+  SpaResult  (*enum_items)           (SpaMonitor              *monitor,
+                                      SpaMonitorItem         **item,
+                                      void                   **state);
+
+};
+
+#define spa_monitor_set_event_callback(m,...) (m)->set_event_callback((m),__VA_ARGS__)
+#define spa_monitor_enum_items(m,...)         (m)->enum_items((m),__VA_ARGS__)
+
+#ifdef __cplusplus
+}  /* extern "C" */
+#endif
+
+#endif /* __SPA_MONITOR_H__ */