tape: implement report_desnity

src/tape/drive/lto/sg_tape.rs

@@ -20,6 +20,9 @@ pub use tape_alert_flags::*;
 mod mam;
 pub use mam::*;
 
+mod report_density;
+pub use report_density::*;
+
 use proxmox::{
     sys::error::SysResult,
     tools::io::{ReadExt, WriteExt},
@@ -103,6 +106,7 @@ pub struct LtoTapeStatus {
 pub struct SgTape {
     file: File,
     info: InquiryInfo,
+    density_code: u8, // drive type
     encryption_key_loaded: bool,
 }
 
@@ -120,9 +124,13 @@ impl SgTape {
         if info.peripheral_type != 1 {
             bail!("not a tape device (peripheral_type = {})", info.peripheral_type);
         }
+
+        let density_code = report_density(&mut file)?;
+
         Ok(Self {
             file,
             info,
+            density_code,
             encryption_key_loaded: false,
         })
     }
@@ -194,18 +202,16 @@ impl SgTape {
         sg_raw.set_timeout(Self::SCSI_TAPE_DEFAULT_TIMEOUT);
         let mut cmd = Vec::new();
 
-        // Try FORMAT first (requires LTO5 or newer)
+        if self.density_code >= 0x58 { // FORMAT requires LTO5 or newer)
             cmd.extend(&[0x04, 0, 0, 0, 0, 0]);
-
-        if let Err(err) = sg_raw.do_command(&cmd) {
-            eprintln!("format failed - using erase insead: {}", err);
-            // try rewind/erase instead
-            self.rewind()?;
-            self.erase_media(fast)?
-        } else {
+            sg_raw.do_command(&cmd)?;
             if !fast {
                 self.erase_media(false)?; // overwrite everything
             }
+        } else {
+            // try rewind/erase instead
+            self.rewind()?;
+            self.erase_media(fast)?
         }
 
         Ok(())

src/tape/drive/lto/sg_tape/report_density.rs

@@ -0,0 +1,69 @@
+use anyhow::{bail, format_err, Error};
+use std::io::Read;
+use endian_trait::Endian;
+use std::os::unix::io::AsRawFd;
+
+use proxmox::tools::io::ReadExt;
+
+use crate::tools::sgutils2::SgRaw;
+
+#[repr(C, packed)]
+#[derive(Endian)]
+struct DesnityDescriptorBlock {
+    primary_density_code: u8,
+    secondary_density_code: u8,
+    flags2: u8,
+    reserved: [u8; 2],
+    bits_per_mm: [u8; 3],
+    media_width: u16,
+    tracks: u16,
+    capacity: u32,
+    organizazion: [u8; 8],
+    density_name: [u8; 8],
+    description: [u8; 20],
+}
+
+// Returns the maximum supported drive density code
+pub fn report_density<F: AsRawFd>(file: &mut F) -> Result<u8, Error> {
+    let alloc_len: u16 = 8192;
+    let mut sg_raw = SgRaw::new(file,  alloc_len as usize)?;
+
+    let mut cmd = Vec::new();
+    cmd.extend(&[0x44, 0, 0, 0, 0, 0, 0]); // REPORT DENSITY SUPPORT (MEDIA=0)
+    cmd.extend(&alloc_len.to_be_bytes()); // alloc len
+    cmd.push(0u8); // control byte
+
+    let data = sg_raw.do_command(&cmd)
+        .map_err(|err| format_err!("report density failed - {}", err))?;
+
+    let mut max_density = 0u8;
+
+    proxmox::try_block!({
+        let mut reader = &data[..];
+
+        let page_len: u16 = unsafe { reader.read_be_value()? };
+        let page_len = page_len as usize;
+
+        if (page_len + 2) > data.len() {
+            bail!("invalid page length {} {}", page_len + 2, data.len());
+        } else {
+            // Note: Quantum hh7 returns the allocation_length instead of real data_len
+            reader = &data[2..page_len+2];
+        }
+        let mut reserved = [0u8; 2];
+        reader.read_exact(&mut reserved)?;
+
+        loop {
+            if reader.is_empty() { break; }
+            let block: DesnityDescriptorBlock = unsafe { reader.read_be_value()? };
+            if block.primary_density_code > max_density {
+                max_density = block.primary_density_code;
+            }
+        }
+
+        Ok(())
+
+    }).map_err(|err| format_err!("decode report density failed - {}", err))?;
+
+    Ok(max_density)
+}