tape: improve code docs

src/tape/drive/linux_tape.rs

@@ -1,3 +1,5 @@
+//! Driver for Linux SCSI tapes
+
 use std::fs::{OpenOptions, File};
 use std::os::unix::fs::OpenOptionsExt;
 use std::os::unix::io::{AsRawFd, FromRawFd};
@@ -49,12 +51,18 @@ use crate::{
     }
 };
 
+/// Linux tape drive status
 #[derive(Debug)]
 pub struct LinuxDriveStatus {
+    /// Size 0 is variable block size mode (default)
     pub blocksize: u32,
+    /// Drive status flags
     pub status: GMTStatusFlags,
+    /// Tape densitiy code (if drive media loaded)
     pub density: Option<TapeDensity>,
+    /// Current file position if known (or -1)
     pub file_number: Option<u32>,
+    /// Current block number if known (or -1)
     pub block_number: Option<u32>,
 }
 

src/tape/drive/mam.rs

@@ -114,6 +114,7 @@ fn read_tape_mam<F: AsRawFd>(file: &mut F) -> Result<Vec<u8>, Error> {
         .map(|v| v.to_vec())
 }
 
+/// Read Medium auxiliary memory attributes (cartridge memory) using raw SCSI command. 
 pub fn read_mam_attributes<F: AsRawFd>(file: &mut F) -> Result<Vec<MamAttribute>, Error> {
 
     let data = read_tape_mam(file)?;

src/tape/drive/mod.rs

@@ -269,6 +269,7 @@ pub fn required_media_changer(
     }
 }
 
+/// Opens a tape drive (this fails if there is no media loaded)
 pub fn open_drive(
     config: &SectionConfigData,
     drive: &str,

src/tape/drive/volume_statistics.rs

@@ -58,6 +58,8 @@ struct LpParameterHeader {
     parameter_len: u8,
 }
 
+
+/// Volume statistics from SCSI log page 17h
 #[derive(Default, Serialize, Deserialize)]
 pub struct Lp17VolumeStatistics {
     pub volume_mounts: u64,