Restructure: scsi/ and aacs/ as module directories

- scsi.rs → scsi/mod.rs (trait, constants, CDB builders) + scsi/linux.rs (SG_IO)
 Ready for scsi/macos.rs and scsi/windows.rs when needed.
- aacs.rs + aacs_handshake.rs → aacs/mod.rs (keys, decrypt) + aacs/handshake.rs (SCSI auth)
- All internal refs use super:: within module, crate:: across modules
- Zero warnings, 31 tests passing

src/scsi/mod.rs

@@ -0,0 +1,138 @@
+//! SCSI/MMC command interface.
+//!
+//! Platform backends are in separate files:
+//!   - `linux.rs` — SG_IO ioctl
+//!   - `macos.rs` — IOKit (planned)
+//!   - `windows.rs` — SPTI (planned)
+
+#[cfg(target_os = "linux")]
+mod linux;
+
+use crate::error::{Error, Result};
+use std::path::Path;
+
+// ── SCSI opcodes (SPC-4, MMC-6) ────────────────────────────────────────────
+
+pub const SCSI_INQUIRY: u8             = 0x12;
+pub const SCSI_READ_CAPACITY: u8       = 0x25;
+pub const SCSI_READ_10: u8             = 0x28;
+pub const SCSI_READ_BUFFER: u8         = 0x3C;
+pub const SCSI_READ_TOC: u8            = 0x43;
+pub const SCSI_GET_CONFIGURATION: u8   = 0x46;
+pub const SCSI_SET_CD_SPEED: u8        = 0xBB;
+pub const SCSI_SEND_KEY: u8            = 0xA3;
+pub const SCSI_REPORT_KEY: u8          = 0xA4;
+pub const SCSI_READ_12: u8             = 0xA8;
+pub const SCSI_READ_DISC_STRUCTURE: u8 = 0xAD;
+
+/// AACS key class for REPORT KEY / SEND KEY commands.
+pub const AACS_KEY_CLASS: u8 = 0x02;
+
+// ── Types ───────────────────────────────────────────────────────────────────
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum DataDirection {
+    None,
+    FromDevice,
+    ToDevice,
+}
+
+#[derive(Debug)]
+pub struct ScsiResult {
+    pub status: u8,
+    pub bytes_transferred: usize,
+    pub sense: [u8; 32],
+}
+
+/// Low-level SCSI transport — one implementation per platform.
+pub trait ScsiTransport {
+    fn execute(
+        &mut self,
+        cdb: &[u8],
+        direction: DataDirection,
+        data: &mut [u8],
+        timeout_ms: u32,
+    ) -> Result<ScsiResult>;
+}
+
+// ── Platform-agnostic open ──────────────────────────────────────────────────
+
+/// Open a SCSI transport for the given device path.
+/// Selects the right backend for the current platform.
+pub fn open(device: &Path) -> Result<Box<dyn ScsiTransport>> {
+    #[cfg(target_os = "linux")]
+    { Ok(Box::new(linux::SgIoTransport::open(device)?)) }
+
+    #[cfg(target_os = "macos")]
+    { Err(Error::DeviceNotFound { path: format!("{}: macOS not yet supported", device.display()) }) }
+
+    #[cfg(target_os = "windows")]
+    { Err(Error::DeviceNotFound { path: format!("{}: Windows not yet supported", device.display()) }) }
+
+    #[cfg(not(any(target_os = "linux", target_os = "macos", target_os = "windows")))]
+    { Err(Error::DeviceNotFound { path: format!("{}: unsupported platform", device.display()) }) }
+}
+
+// ── CDB builders (platform-agnostic) ────────────────────────────────────────
+
+/// SCSI INQUIRY response.
+#[derive(Debug, Clone)]
+pub struct InquiryResult {
+    pub vendor_id: String,
+    pub model: String,
+    pub firmware: String,
+    pub raw: Vec<u8>,
+}
+
+/// Send INQUIRY and parse standard response fields.
+pub fn inquiry(scsi: &mut dyn ScsiTransport) -> Result<InquiryResult> {
+    let cdb = [SCSI_INQUIRY, 0x00, 0x00, 0x00, 0x60, 0x00];
+    let mut buf = [0u8; 96];
+    scsi.execute(&cdb, DataDirection::FromDevice, &mut buf, 5_000)?;
+
+    Ok(InquiryResult {
+        vendor_id: String::from_utf8_lossy(&buf[8..16]).trim().to_string(),
+        model: String::from_utf8_lossy(&buf[16..32]).trim().to_string(),
+        firmware: String::from_utf8_lossy(&buf[32..36]).trim().to_string(),
+        raw: buf.to_vec(),
+    })
+}
+
+/// Send GET CONFIGURATION for feature 0x010C (Firmware Information).
+pub fn get_config_010c(scsi: &mut dyn ScsiTransport) -> Result<Vec<u8>> {
+    let cdb = [SCSI_GET_CONFIGURATION, 0x02, 0x01, 0x0C, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00];
+    let mut buf = [0u8; 16];
+    scsi.execute(&cdb, DataDirection::FromDevice, &mut buf, 5_000)?;
+    Ok(buf.to_vec())
+}
+
+/// Build a READ BUFFER CDB.
+pub fn build_read_buffer(mode: u8, buffer_id: u8, offset: u32, length: u32) -> [u8; 10] {
+    [
+        SCSI_READ_BUFFER, mode, buffer_id,
+        (offset >> 16) as u8, (offset >> 8) as u8, offset as u8,
+        (length >> 16) as u8, (length >> 8) as u8, length as u8,
+        0x00,
+    ]
+}
+
+/// Build a SET CD SPEED CDB.
+pub fn build_set_cd_speed(read_speed: u16) -> [u8; 12] {
+    [
+        SCSI_SET_CD_SPEED, 0x00,
+        (read_speed >> 8) as u8, read_speed as u8,
+        0xFF, 0xFF,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    ]
+}
+
+/// Build a READ(10) CDB with the raw read flag.
+pub fn build_read10_raw(lba: u32, count: u16) -> [u8; 10] {
+    [
+        SCSI_READ_10, 0x08,
+        (lba >> 24) as u8, (lba >> 16) as u8, (lba >> 8) as u8, lba as u8,
+        0x00,
+        (count >> 8) as u8, count as u8,
+        0x00,
+    ]
+}