73         count: usize,          // 读取lba的数量  in read_at()
78         let check_length = ((count - 1) >> 4) + 1; // prdt length  in read_at()
79         if count * 512 > buf.len() || check_length > 8_usize {  in read_at()
83         } else if count == 0 {  in read_at()
138         let mut tmp_count = count;  in read_at()
185         volatile_write!(cmdfis.countl, (count & 0xFF) as u8);  in read_at()
186         volatile_write!(cmdfis.counth, ((count >> 8) & 0xFF) as u8);  in read_at()
223         return Ok(count * 512);  in read_at()
229         count: usize,  in write_at()
234         let check_length = ((count - 1) >> 4) + 1; // prdt length  in write_at()
235         if count * 512 > buf.len() || check_length > 8 {  in write_at()
238         } else if count == 0 {  in write_at()
302         let mut tmp_count = count;  in write_at()
352         volatile_write!(cmdfis.countl, (count & 0xFF) as u8);  in write_at()
353         volatile_write!(cmdfis.counth, ((count >> 8) & 0xFF) as u8);  in write_at()
372         return Ok(count * 512);  in write_at()
566         count: usize,          // 读取lba的数量  in read_at_sync()
569         self.inner().read_at(lba_id_start, count, buf)  in read_at_sync()
576         count: usize,  in write_at_sync()
579         self.inner().write_at(lba_id_start, count, buf)  in write_at_sync()