firmware: mirror BD-disable wire change to STATE_BD_DISABLE (0x02)

Lockstep with freemkv-fw BD-refuse stealth fix: the BD force-disable wire
value moves from STATE_OFF (0x00, the SRAM boot value) to a distinct
sentinel STATE_BD_DISABLE (0x02), so an unarmed firmware image stays
OEM-identical. disable_bd() now sends 0x02; add the const and align the
Feature::Bd / Feature::Uhd ABI-mirror docs (enable dir / STATE_OFF are
OEM no-ops).

src/firmware/mod.rs

@@ -83,6 +83,11 @@ pub const SPEED_MAX: u8 = 0x01;
 /// valid-empty. Destructive; NOT undone by [`Verb::Reset`]. `0x02`.
 pub const HRL_WIPE_ONCE: u8 = 0x02;
 
+/// [`Feature::Bd`] state: force-refuse BD (AACS 1.0) discs (`0x02`). A distinct
+/// sentinel — NOT [`STATE_OFF`] (`0x00`, the SRAM boot value) — so an unarmed image
+/// leaves BD engaged (OEM). Mirrors the firmware ABI `STATE_BD_DISABLE`.
+pub const STATE_BD_DISABLE: u8 = 0x02;
+
 /// [`Feature::Region`] state: force BD region A (`0x2A`). See [`BdRegion`].
 pub const REGION_BD_A: u8 = 0x2A;
 /// [`Feature::Region`] state: force BD region B (`0x2B`).
@@ -121,9 +126,12 @@ pub enum Feature {
     /// Region (RPC) control. [`STATE_ON`] = region-free; `0x11..=0x18` = force
     /// DVD region 1..8; [`REGION_BD_A`]/`_B`/`_C` = force BD region A/B/C.
     Region = 0x02,
-    /// UHD (AACS 2.0) capability gate.
+    /// UHD (AACS 2.0) capability gate. [`STATE_ON`] = force enabled; [`STATE_OFF`]
+    /// is a reserved/OEM no-op (only the enable direction is emitted).
     Uhd = 0x03,
-    /// Blu-ray (AACS 1.0) capability gate.
+    /// Blu-ray (AACS 1.0) capability gate. [`STATE_BD_DISABLE`] (`0x02`) =
+    /// force-refuse BD discs; passthrough/`0x00` boot/[`STATE_ON`] = OEM (engaged —
+    /// the enable direction is a no-op, OEM already engages BD).
     Bd = 0x04,
     /// Host Revocation List handling. [`STATE_ON`] = skip lookup;
     /// [`HRL_WIPE_ONCE`] = one-time permanent wipe.
@@ -534,9 +542,11 @@ impl<'a> FirmwareControl<'a> {
     pub fn enable_bd(&mut self) -> Result<()> {
         self.set(Feature::Bd, STATE_ON)
     }
-    /// Force the Blu-ray capability gate off.
+    /// Force the Blu-ray capability gate off (drive refuses BD discs). Sends
+    /// [`STATE_BD_DISABLE`] (`0x02`) — a distinct sentinel, NOT `0x00` (the SRAM boot
+    /// value) — so an unarmed image stays OEM-behaviour-identical (BD engaged).
     pub fn disable_bd(&mut self) -> Result<()> {
-        self.set(Feature::Bd, STATE_OFF)
+        self.set(Feature::Bd, STATE_BD_DISABLE)
     }
     /// Skip the HRL lookup (revoked certs accepted; non-destructive).
     pub fn skip_hrl(&mut self) -> Result<()> {

src/firmware/mod_tests.rs

@@ -39,6 +39,7 @@ fn state_and_frame_constants_match_abi() {
     assert_eq!(STATE_ON, 0x01);
     assert_eq!(SPEED_MAX, 0x01);
     assert_eq!(HRL_WIPE_ONCE, 0x02);
+    assert_eq!(STATE_BD_DISABLE, 0x02);
     assert_eq!([REGION_BD_A, REGION_BD_B, REGION_BD_C], [0x2A, 0x2B, 0x2C]);
     assert_eq!(REGION_DVD_BASE, 0x10);
 }
@@ -348,7 +349,7 @@ fn typed_setters_issue_expected_set_cdbs() {
         fw.unlock_speed().unwrap();
     }
     assert_eq!(m.cdbs[0], build_set_cdb(Feature::Uhd, STATE_ON));
-    assert_eq!(m.cdbs[1], build_set_cdb(Feature::Bd, STATE_OFF));
+    assert_eq!(m.cdbs[1], build_set_cdb(Feature::Bd, STATE_BD_DISABLE));
     assert_eq!(m.cdbs[2], build_set_cdb(Feature::Hrl, STATE_ON));
     assert_eq!(m.cdbs[3], build_set_cdb(Feature::Hrl, HRL_WIPE_ONCE));
     assert_eq!(m.cdbs[4], build_set_cdb(Feature::Ake, STATE_ON));