Hi, folks:
 I found the reason and fix it.

I trace system call chown&chmod, then found(fs/attr.c):

*if (inode->i_op && inode->i_op->setattr) *

*{*

*                   error = inode->i_op->setattr(dentry,
attr);               //regular file *

*}*

*Else*

*{                                    //device file   for yaffs *

*         error = inode_change_ok(inode, attr);                      *

*         if (!error) {*

*                            if ((ia_valid & ATTR_UID && attr->ia_uid !=
inode->i_uid) ||*

*                                (ia_valid & ATTR_GID && attr->ia_gid !=
inode->i_gid))*

*                                     error = vfs_dq_transfer(inode, attr) ?
*

*                                               -EDQUOT : 0;*

*                            if (!error)*

*                                     error = inode_setattr(inode, attr);*

*         }*

*}*

    when do chown&chmod on device file,the field *inode->i_op*   not
assigned , so I assign the value in yaffs_fs.c




         static const struct inode_operations
yaffs_special_inode_operations = {

         .setattr = yaffs_setattr,

};



 static void yaffs_FillInodeFromObject(struct inode *inode, yaffs_Object
*obj)

{

................................................

switch (obj->yst_mode & S_IFMT) {

                   default:    /* fifo, device or socket */

                  inode->i_op = &yaffs_special_inode_operations;

#if (LINUX_VERSION_CODE > KERNEL_VERSION(2, 5, 0))



                            init_special_inode(inode, obj->yst_mode,


old_decode_dev(obj->yst_rdev));

#else

                            init_special_inode(inode, obj->yst_mode,

                                               (dev_t) (obj->yst_rdev));

#endif

                            break;

                   case S_IFREG: /* file */

                            inode->i_op = &yaffs_file_inode_operations;

                            inode->i_fop = &yaffs_file_operations;

                            inode->i_mapping->a_ops =

                                     &yaffs_file_address_operations;

                            break;

                   case S_IFDIR:  /* directory */

                            inode->i_op = &yaffs_dir_inode_operations;

                            inode->i_fop = &yaffs_dir_operations;

                            break;

                   case S_IFLNK:  /* symlink */

                            inode->i_op = &yaffs_symlink_inode_operations;

                            break;

                   }

...................................................

}