v4l2-ioctl.c的一些学习和整理

可以发现，这个宏用的很好，简洁易扩展，自己写代码可以学习下

#define IOCTL_INFO(_ioctl, _func, _debug, _flags)		\
	[_IOC_NR(_ioctl)] = {					\
		.ioctl = _ioctl,				\
		.flags = _flags,				\
		.name = #_ioctl,				\
		.func = _func,					\
		.debug = _debug,				\
	}

static const char *v4l2_memory_names[] = {
	[V4L2_MEMORY_MMAP]    = "mmap",
	[V4L2_MEMORY_USERPTR] = "userptr",
	[V4L2_MEMORY_OVERLAY] = "overlay",
	[V4L2_MEMORY_DMABUF] = "dmabuf",
};