16 use system_error::SystemError;
84     ) -> Result<(), SystemError> {  in open()  argument
85         Err(SystemError::ENOSYS)  in open()
88     fn close(&self, _data: SpinLockGuard<FilePrivateData>) -> Result<(), SystemError> {  in close()  argument
89         Err(SystemError::ENOSYS)  in close()
92     fn metadata(&self) -> Result<Metadata, SystemError> {  in metadata()  argument
100     fn list(&self) -> Result<Vec<String>, SystemError> {  in list()  argument
101         Err(SystemError::ENOSYS)  in list()
104     fn set_metadata(&self, metadata: &Metadata) -> Result<(), SystemError> {  in set_metadata()  argument
123     ) -> Result<usize, SystemError> {  in read_at()  argument
125             return Err(SystemError::EINVAL);  in read_at()
132         return Err(SystemError::EINVAL);  in read_at()
142     ) -> Result<usize, SystemError> {  in write_at()  argument
144             return Err(SystemError::EINVAL);  in write_at()
151         return Err(SystemError::EINVAL);  in write_at()