int register_blockdriver(FAR const char *path,						//文件名
                         FAR const struct block_operations *bops,	//结构体
                         mode_t mode, FAR void *priv)
{}

struct block_operations
{
  int     (*open)(FAR struct inode *inode);
  int     (*close)(FAR struct inode *inode);
  ssize_t (*read)(FAR struct inode *inode, FAR unsigned char *buffer,
            unsigned long long start_sector, unsigned int nsectors);
  ssize_t (*write)(FAR struct inode *inode, FAR const unsigned char *buffer,
            unsigned long long start_sector, unsigned int nsectors);
  int     (*geometry)(FAR struct inode *inode, FAR struct geometry *geometry); //获取内部结构
  int     (*ioctl)(FAR struct inode *inode, int cmd, unsigned long arg);
  int     (*unlink)(FAR struct inode *inode);
};

struct geometry //几何设备
{
  bool   geo_available;    /* true: The device is available 是否可用 */
  bool   geo_mediachanged; /* true: The media has changed since last query */
  bool   geo_writeenabled; /* true: It is okay to write to this device 是否可写 */
  unsigned long long geo_nsectors;     /* Number of sectors on the device 多少个扇区*/
  size_t geo_sectorsize;   /* Size of one sector 每个扇区的大小*/
};