Add use_v4lplugin flag to enable v4l2 library

third_party/v4l-utils/lib/include/libv4l-plugin.h

+/*
+* Copyright (C) 2010 Nokia Corporation <multimedia@maemo.org>
+
+* This program is free software; you can redistribute it and/or modify
+* it under the terms of the GNU Lesser General Public License as published by
+* the Free Software Foundation; either version 2.1 of the License, or
+* (at your option) any later version.
+*
+* This program 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
+* Lesser General Public License for more details.
+*
+* You should have received a copy of the GNU Lesser General Public License
+* along with this program; if not, write to the Free Software
+* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+*/
+
+#ifndef __LIBV4L_PLUGIN_H
+#define __LIBV4L_PLUGIN_H
+
+#include <sys/types.h>
+
+/* Structure libv4l_dev_ops holds the calls from libv4ls to video nodes.
+   They can be normal open/close/ioctl etc. or any of them may be replaced
+   with a callback by a loaded plugin.
+*/
+
+struct libv4l_dev_ops {
+    void * (*init)(int fd);
+    void (*close)(void *dev_ops_priv);
+    int (*ioctl)(void *dev_ops_priv, int fd, unsigned long int request, void *arg);
+    ssize_t (*read)(void *dev_ops_priv, int fd, void *buffer, size_t n);
+    ssize_t (*write)(void *dev_ops_priv, int fd, const void *buffer, size_t n);
+    /* For future plugin API extension, plugins implementing the current API
+       must set these all to NULL, as future versions may check for these */
+    void (*reserved1)(void);
+    void (*reserved2)(void);
+    void (*reserved3)(void);
+    void (*reserved4)(void);
+    void (*reserved5)(void);
+    void (*reserved6)(void);
+    void (*reserved7)(void);
+};
+
+#endif