fix: address PR review feedback for MIDI 2.0 drivers

Host driver (midi2_host.c):
- midih2_open() now returns actual parsed length instead of max_len,
  preventing composite device interface conflicts
- Parsers (alt0/alt1) refactored to return const uint8_t* end pointer
  following midi_host.c switch/case pattern
- Alt 1 CS Endpoint now parses MIDI 2.0 layout (bNumGrpTrmBlk at
  offset 3 with MIDI_CS_ENDPOINT_GENERAL_2_0 subtype check) instead
  of reusing MIDI 1.0 struct (bNumEmbMIDIJack)
- midih2_set_config() now issues SET_INTERFACE control request via
  tuh_interface_set() before completing configuration. Falls back to
  alt 0 if SET_INTERFACE fails
- Extracted midih2_set_config_complete() and midih2_set_interface_cb()
  for async SET_INTERFACE handling

Device driver (midi2_device.c):
- midi2d_open() skip loop now checks bInterfaceNumber, stopping at
  interfaces that belong to other functions in composite devices
- SET_INTERFACE handler now rejects alt > 1 (returns false/stall)
- Named constants for GTB descriptor types and MIDI protocol values

Descriptor macros (usbd.h):
- TUD_MIDI2_DESC_ALT1_HEAD: iInterface set to 0 (consistent with
  Alt 0), wTotalLength now uses TUD_MIDI2_DESC_ALT1_CS_LEN to cover
  all Alt 1 class-specific descriptors
- TUD_MIDI2_DESC_ALT1_EP: now accepts GTB ID list via variadic args,
  emitting complete CS endpoint descriptor

Host example:
- CMakeLists.txt restricted to rp2040 family (display.c requires
  Pico SDK headers)
- display.c: null terminator after strncpy in log scroll

Documentation:
- class_drivers.rst updated to reflect SET_INTERFACE behavior and
  auto-select with fallback

Addresses: Codex P1 (#1, #2, #3), Copilot (#4-#9)

1 files changed, 12 insertions, 12 deletions

diff --git a/src/device/usbd.h b/src/device/usbd.h
index af37eff56..a9f4c5f08 100644
--- a/src/device/usbd.h
+++ b/src/device/usbd.h
@@ -429,18 +429,20 @@ bool tud_vendor_control_xfer_cb(uint8_t rhport, uint8_t stage, tusb_control_requ
 //--------------------------------------------------------------------+
 
 // Alt Setting 1: MS Interface + MS Header (bcdMSC=0x0200)
+// wTotalLength covers MS Header + all CS Endpoint descriptors
+#define TUD_MIDI2_DESC_ALT1_CS_LEN(_numgtbs) (7 + (4 + (_numgtbs)) * 2)
 #define TUD_MIDI2_DESC_ALT1_HEAD_LEN (9 + 7)
-#define TUD_MIDI2_DESC_ALT1_HEAD(_itfnum, _stridx) \
+#define TUD_MIDI2_DESC_ALT1_HEAD(_itfnum, _stridx, _numgtbs) \
   /* MIDI Streaming Interface, Alt Setting 1 */\
-  9, TUSB_DESC_INTERFACE, (uint8_t)((_itfnum) + 1), 1, 2, TUSB_CLASS_AUDIO, AUDIO_SUBCLASS_MIDI_STREAMING, AUDIO_FUNC_PROTOCOL_CODE_UNDEF, _stridx,\
-  /* MS Header (MIDI 2.0) */\
-  7, TUSB_DESC_CS_INTERFACE, MIDI_CS_INTERFACE_HEADER, U16_TO_U8S_LE(0x0200), U16_TO_U8S_LE(7)
+  9, TUSB_DESC_INTERFACE, (uint8_t)((_itfnum) + 1), 1, 2, TUSB_CLASS_AUDIO, AUDIO_SUBCLASS_MIDI_STREAMING, AUDIO_FUNC_PROTOCOL_CODE_UNDEF, 0,\
+  /* MS Header (MIDI 2.0): wTotalLength = header + 2x CS Endpoint */\
+  7, TUSB_DESC_CS_INTERFACE, MIDI_CS_INTERFACE_HEADER, U16_TO_U8S_LE(0x0200), U16_TO_U8S_LE(TUD_MIDI2_DESC_ALT1_CS_LEN(_numgtbs))
 
-// Alt Setting 1: Standard USB Endpoint (7 bytes) + CS Endpoint (subtype 0x02)
+// Alt Setting 1: Standard USB Endpoint (7 bytes) + CS Endpoint General 2.0
 #define TUD_MIDI2_DESC_ALT1_EP_LEN(_numgtbs) (7 + 4 + (_numgtbs))
-#define TUD_MIDI2_DESC_ALT1_EP(_ep, _epsize, _numgtbs) \
+#define TUD_MIDI2_DESC_ALT1_EP(_ep, _epsize, _numgtbs, ...) \
   7, TUSB_DESC_ENDPOINT, _ep, TUSB_XFER_BULK, U16_TO_U8S_LE(_epsize), 0, \
-  (uint8_t)(4 + (_numgtbs)), TUSB_DESC_CS_ENDPOINT, MIDI_CS_ENDPOINT_GENERAL_2_0, _numgtbs
+  (uint8_t)(4 + (_numgtbs)), TUSB_DESC_CS_ENDPOINT, MIDI_CS_ENDPOINT_GENERAL_2_0, _numgtbs, ## __VA_ARGS__
 
 // Total length: Alt 0 (MIDI 1.0) + Alt 1 (UMP)
 #define TUD_MIDI2_DESC_LEN (TUD_MIDI_DESC_LEN + TUD_MIDI2_DESC_ALT1_HEAD_LEN + TUD_MIDI2_DESC_ALT1_EP_LEN(1) * 2)
@@ -455,11 +457,9 @@ bool tud_vendor_control_xfer_cb(uint8_t rhport, uint8_t stage, tusb_control_requ
   TUD_MIDI_DESC_EP(_epin, _epsize, 1),\
   TUD_MIDI_JACKID_OUT_EMB(1),\
   /* Alt Setting 1 (UMP) */\
-  TUD_MIDI2_DESC_ALT1_HEAD(_itfnum, _stridx),\
-  TUD_MIDI2_DESC_ALT1_EP(_epout, _epsize, 1),\
-  1, /* bAssoGrpTrmBlkID = 1 */\
-  TUD_MIDI2_DESC_ALT1_EP(_epin, _epsize, 1),\
-  1  /* bAssoGrpTrmBlkID = 1 */
+  TUD_MIDI2_DESC_ALT1_HEAD(_itfnum, _stridx, 1),\
+  TUD_MIDI2_DESC_ALT1_EP(_epout, _epsize, 1, 1 /* bAssoGrpTrmBlkID */),\
+  TUD_MIDI2_DESC_ALT1_EP(_epin, _epsize, 1, 1 /* bAssoGrpTrmBlkID */)
 
 //--------------------------------------------------------------------+
 // Audio Descriptor Templates