int yaffs2_checkpt_wr(yaffs_dev_t *dev, const void *data, int n_bytes);
int yaffs2_checkpt_rd(yaffs_dev_t *dev, void *data, int n_bytes);
int yaffs2_checkpt_wr(yaffs_dev_t *dev, const void *data, int n_bytes);
int yaffs2_checkpt_rd(yaffs_dev_t *dev, void *data, int n_bytes);