2.6 kernel
struct v4l2_event {
	__u32				type;
	union {
		__u8			data[64];
	} u;
	__u32				pending;
	__u32				sequence;
	struct timespec			timestamp;
	__u32				reserved[9];
};

3.5 kernel
struct v4l2_event {
	__u32				type;
	union {
		struct v4l2_event_vsync		vsync;
		struct v4l2_event_ctrl		ctrl;
		struct v4l2_event_frame_sync	frame_sync;
		__u8				data[64];
	} u;
	__u32				pending;
	__u32				sequence;
	struct timespec			timestamp;
	__u32				id;
	__u32				reserved[8];
};