optical vs block batch sizing

src/disc/mod.rs

@@ -1545,7 +1545,7 @@ impl Disc {
         let batch: u16 = match opts.batch_sectors {
             Some(b) => b,
             None if opts.skip_on_error => ecc_sectors(self.format),
-            None => DEFAULT_BATCH_SECTORS,
+            None => DEFAULT_BATCH_SECTORS_OPTICAL,
         };
 
         // Pre-compute the list of NonTried regions before handing the
@@ -3327,7 +3327,8 @@ impl Disc {
 }
 
 const MAX_BATCH_SECTORS: u16 = 510;
-const DEFAULT_BATCH_SECTORS: u16 = 60;
+const DEFAULT_BATCH_SECTORS_OPTICAL: u16 = 60;
+const DEFAULT_BATCH_SECTORS_BLOCK: u16 = 8192;
 const MIN_BATCH_SECTORS: u16 = 3;
 
 pub(crate) fn ecc_sectors(format: DiscFormat) -> u16 {
@@ -3404,15 +3405,33 @@ mod severity_tests {
 }
 
 /// Detect the maximum transfer size in sectors for a device.
-/// Reads /sys/block/<dev>/queue/max_hw_sectors_kb on Linux.
-/// For sg devices, resolves the corresponding block device via sysfs.
-/// Returns a value aligned to 3 sectors (one aligned unit).
 pub fn detect_max_batch_sectors(device_path: &str) -> u16 {
     let dev_name = device_path.rsplit('/').next().unwrap_or("");
     if dev_name.is_empty() {
-        return DEFAULT_BATCH_SECTORS;
+        return DEFAULT_BATCH_SECTORS_OPTICAL;
     }
 
+    // Check if optical drive (0x05 = CD/DVD)
+   let is_optical = (|| -> bool {
+        use std::path::Path;
+        let scsi_device_dir = format!("/sys/class/scsi_device/");
+        if let Ok(entries) = std::fs::read_dir(&scsi_device_dir) {
+            for entry in entries.flatten() {
+                let device_type_path = entry.path().join("device/type");
+                if Path::new(&device_type_path).exists() {
+                    if let Ok(content) = std::fs::read_to_string(&device_type_path) {
+                        // Type 0x05 (decimal 5) = CD/DVD drive
+                        if content.trim().parse::<u32>() == Ok(5) {
+                            return true;
+                        }
+                    }
+                }
+            }
+        }
+        false
+    })();
+
+    if is_optical {
         // For sg devices, find the corresponding block device name
         let block_name = if dev_name.starts_with("sg") {
             let block_dir = format!("/sys/class/scsi_generic/{dev_name}/device/block");
@@ -3439,8 +3458,10 @@ pub fn detect_max_batch_sectors(device_path: &str) -> u16 {
                 }
             }
         }
-    // Fallback: safe default well under typical kernel limits
+     DEFAULT_BATCH_SECTORS_OPTICAL
-    DEFAULT_BATCH_SECTORS
+    } else {
+        DEFAULT_BATCH_SECTORS_BLOCK
+    }
 }
 
 // ─── Format helpers ────────────────────────────────────────────────────────