Structured error codes: E1000-E5000, no user-facing text in library

Error codes:
 1000-1001: device errors (not found, permission)
 2000-2002: profile errors (unsupported, not found, parse)
 3000-3003: unlock errors (failed, signature, not unlocked, not calibrated)
 4000-4001: SCSI errors (command failed, timeout)
 5000: I/O errors

All errors carry structured data (vendor_id, opcode, etc).
Applications format their own user-facing messages.
Library returns code + data, never English text.

src/scsi.rs

@@ -76,7 +76,7 @@ impl SgIoTransport {
 
         let fd = unsafe { libc::open(c_path.as_ptr() as *const libc::c_char, libc::O_RDWR | libc::O_NONBLOCK) };
         if fd < 0 {
-            return Err(Error::DeviceNotFound(device.display().to_string()));
+            return Err(Error::DeviceNotFound { path: device.display().to_string() });
         }
         Ok(SgIoTransport { fd })
     }
@@ -120,16 +120,17 @@ impl ScsiTransport for SgIoTransport {
         };
 
         if ret < 0 {
-            return Err(Error::Io(std::io::Error::last_os_error()));
+            return Err(Error::IoError { source: std::io::Error::last_os_error() });
         }
 
         let bytes_transferred = (data.len() as i32 - hdr.resid) as usize;
 
         if hdr.status != 0 {
+            let sense_key = if hdr.sb_len_wr > 2 { sense[2] & 0x0F } else { 0 };
             return Err(Error::ScsiError {
-                cdb: cdb.to_vec(),
+                opcode: cdb[0],
                 status: hdr.status,
-                sense: sense[..hdr.sb_len_wr as usize].to_vec(),
+                sense_key,
             });
         }