20 const BLK_SIZE_LOG2_LIMIT: u8 = 12; // 设定块设备的块大小不能超过 1 << 12.
35     fn read_at(&self, offset: usize, len: usize, buf: &mut [u8]) -> Result<usize, SystemError>;  in read_at()
42     fn write_at(&self, offset: usize, len: usize, buf: &[u8]) -> Result<usize, SystemError>;  in write_at()
64         buf: &mut [u8],  in read_at()  argument
78         buf: &[u8],  in write_at()  argument
86     fn blk_size_log2(&self) -> u8;  in blk_size_log2()  argument
109     fn read_at(&self, offset: usize, len: usize, buf: &mut [u8]) -> Result<usize, SystemError> {  in read_at()
145     fn write_at(&self, offset: usize, len: usize, buf: &[u8]) -> Result<usize, SystemError> {  in write_at()
192     pub blk_size_log2: u8,
204     pub blk_size_log2: u8,
209     pub fn new(start_addr: usize, end_addr: usize, blk_size_log2: u8) -> BlockIter {  in new()
217     pub fn new_multiblock(start_addr: usize, end_addr: usize, blk_size_log2: u8) -> BlockIter {  in new_multiblock()