Step 7.5b1: cspot (philippe44 fork) builds and links on the P4

- external/cspot: git submodule, pinned to philippe44/cspot 3010349
  (bell ed2d6e9); GPL-3.0.
- components/spotify: project component wrapping cspot. bell trimmed to
  what cspot needs (Tremor Vorbis; no codec wrapper, sinks, MQTT, web
  server, fmt, regex; cJSON from IDF). Xtensa biquad assembly filtered
  out (P4 is RISC-V). CMAKE_POLICY_VERSION_MINIMUM 3.5 for CMake 4.
- Patches in components/spotify/patches, applied at configure time:
  nanopb generator works with protobuf >= 5 (MakeClass removed);
  URLParser.cpp missing <cstdio>/<cstring> for GCC 14.
- CONFIG_COMPILER_CXX_EXCEPTIONS=y (cspot needs exceptions).
- spotify_init() only builds a LoginBlob (link check).
- CLAUDE.md: submodule init and IDF-venv Python packages for nanopb.
- Verified on board: "cspot linked: device "P4 AES67", zeroconf info 588
  bytes"; HLS still playing, PTP locked; image 1.83 MB (70% free).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "external/cspot"]
+	path = external/cspot
+	url = https://github.com/philippe44/cspot.git

CLAUDE.md

@@ -27,6 +27,7 @@ Repo: https://gitea.apointless.space/bsncubed/aes67-ESP32-P4
   - Our board: **32 MB** flash (GigaDevice c8/4019). App slots must stay below 16 MB (cache mapping above 16 MB is experimental in IDF).
   - Rev < 3 also limits Espressif's prebuilt audio libraries: `esp_audio_codec` must stay < 2.6 and `esp_audio_effects` < 1.4 (newer versions use P4 assembly that needs rev >= 3; the build fails with a message saying so). Check this for any new Espressif binary component.
 - Embed `web/index.html` via `EMBED_TXTFILES` in `aes67_web`.
+- cspot (Spotify, `external/cspot` git submodule, philippe44 fork, pinned): after cloning run `git submodule update --init external/cspot && git -C external/cspot submodule update --init cspot/bell`. Its nanopb code generator needs, in the IDF Python env: `python -m pip install protobuf grpcio-tools 'setuptools<81'` (after `. export.sh`). Our fixes to cspot/bell live in `components/spotify/patches/{cspot,bell}/*.patch` and are applied automatically at configure time; don't edit the submodule directly, add a patch.
 - Flash over the network (normal way since step 2b; keep USB for recovery):
   `curl -f --data-binary @build/aes67_p4.bin -H 'Content-Type: application/octet-stream' http://p4-aes67/api/ota`
   The board reboots into the new image on trial; check `GET /api/ota` shows the new version with `pending_verify: false`.

components/spotify/CMakeLists.txt

@@ -0,0 +1,49 @@
+# Spotify Connect via cspot (philippe44 fork, git submodule external/cspot). GPL-3.0.
+# Project component (not part of the reusable aes67_* core).
+idf_component_register(SRCS "spotify.cpp"
+                       INCLUDE_DIRS "include"
+                       PRIV_REQUIRES espressif__mdns mbedtls json pthread lwip esp_timer)
+
+# bell: only what cspot needs (Tremor Vorbis inside; no codec wrapper, sinks, MQTT, web server).
+set(BELL_DISABLE_CODECS ON CACHE BOOL "" FORCE)
+set(BELL_DISABLE_SINKS ON CACHE BOOL "" FORCE)
+set(BELL_DISABLE_MQTT ON CACHE BOOL "" FORCE)
+set(BELL_DISABLE_WEBSERVER ON CACHE BOOL "" FORCE)
+set(BELL_DISABLE_FMT ON CACHE BOOL "" FORCE)
+set(BELL_DISABLE_REGEX ON CACHE BOOL "" FORCE)
+set(BELL_ONLY_CJSON ON CACHE BOOL "" FORCE)
+set(BELL_EXTERNAL_CJSON idf::json CACHE STRING "" FORCE)
+option(BUILD_TESTING OFF)
+
+# Our fixes to the pinned cspot / bell sources (newer GCC, protobuf, CMake), kept as patch files:
+# patches/cspot/*.patch apply in external/cspot, patches/bell/*.patch in external/cspot/cspot/bell.
+# Each is applied once (skipped when it already reverse-applies).
+function(spotify_apply_patches dir repo)
+    file(GLOB patches "${CMAKE_CURRENT_LIST_DIR}/patches/${dir}/*.patch")
+    list(SORT patches)
+    foreach(p ${patches})
+        execute_process(COMMAND git apply --reverse --check "${p}" WORKING_DIRECTORY "${repo}"
+                        RESULT_VARIABLE applied OUTPUT_QUIET ERROR_QUIET)
+        if(NOT applied EQUAL 0)
+            execute_process(COMMAND git apply "${p}" WORKING_DIRECTORY "${repo}" RESULT_VARIABLE rc)
+            if(NOT rc EQUAL 0)
+                message(FATAL_ERROR "spotify: patch does not apply: ${p}")
+            endif()
+            message(STATUS "spotify: applied ${p}")
+        endif()
+    endforeach()
+endfunction()
+spotify_apply_patches(cspot "${PROJECT_DIR}/external/cspot")
+spotify_apply_patches(bell "${PROJECT_DIR}/external/cspot/cspot/bell")
+
+# cspot/bell declare cmake_minimum_required(2.8.12); CMake 4 rejects < 3.5 unless told otherwise.
+set(CMAKE_POLICY_VERSION_MINIMUM 3.5)
+add_subdirectory(${PROJECT_DIR}/external/cspot/cspot ${CMAKE_CURRENT_BINARY_DIR}/cspot)
+
+# bell adds Xtensa (ESP32) assembly for a DSP biquad; the P4 is RISC-V and cspot does not use it.
+get_target_property(BELL_SRCS bell SOURCES)
+list(FILTER BELL_SRCS EXCLUDE REGEX "\\.S$")
+set_target_properties(bell PROPERTIES SOURCES "${BELL_SRCS}")
+
+target_link_libraries(${COMPONENT_LIB} PRIVATE cspot)
+target_compile_options(${COMPONENT_LIB} PRIVATE -std=gnu++20)

components/spotify/include/spotify.h

@@ -0,0 +1,14 @@
+// Spotify Connect (cspot). Project code; GPL-3.0 through cspot.
+#pragma once
+
+#include "esp_err.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+esp_err_t spotify_init(const char *device_name);
+
+#ifdef __cplusplus
+}
+#endif

components/spotify/patches/bell/0001-nanopb-generator-protobuf5.patch

@@ -0,0 +1,18 @@
+diff --git a/external/nanopb/generator/nanopb_generator.py b/external/nanopb/generator/nanopb_generator.py
+index e40f18b..64dad5e 100755
+--- a/external/nanopb/generator/nanopb_generator.py
++++ b/external/nanopb/generator/nanopb_generator.py
+@@ -1463,7 +1463,12 @@ class Message(ProtoElement):
+         optional_only.ClearField(str('extension'))
+         optional_only.ClearField(str('enum_type'))
+         desc = google.protobuf.descriptor.MakeDescriptor(optional_only)
+-        msg = reflection.MakeClass(desc)()
++        # protobuf >= 5 removed reflection.MakeClass (patch for this project)
++        try:
++            msg = reflection.MakeClass(desc)()
++        except AttributeError:
++            from google.protobuf import message_factory
++            msg = message_factory.GetMessageClass(desc)()
+ 
+         for field in optional_only.field:
+             if field.type == FieldD.TYPE_STRING:

components/spotify/patches/bell/0002-urlparser-includes.patch

@@ -0,0 +1,13 @@
+diff --git a/main/io/URLParser.cpp b/main/io/URLParser.cpp
+index 4a50ab1..af679ec 100644
+--- a/main/io/URLParser.cpp
++++ b/main/io/URLParser.cpp
+@@ -1,5 +1,8 @@
+ #include "URLParser.h"
+ 
++#include <cstdio>   // sscanf (GCC 14 / ESP-IDF 5.5: not included transitively)
++#include <cstring>  // strstr
++
+ namespace bell {
+ 
+ #ifdef BELL_DISABLE_REGEX

components/spotify/spotify.cpp

@@ -0,0 +1,17 @@
+#include "spotify.h"
+
+#include <memory>
+
+#include "LoginBlob.h"
+#include "esp_log.h"
+
+static const char *TAG = "spotify";
+
+// Step 7.5b1: link check only. Zeroconf, login and audio follow in b2/b3.
+extern "C" esp_err_t spotify_init(const char *device_name)
+{
+    auto blob = std::make_shared<cspot::LoginBlob>(device_name);
+    std::string info = blob->buildZeroconfInfo();
+    ESP_LOGI(TAG, "cspot linked: device \"%s\", zeroconf info %u bytes", device_name, (unsigned)info.size());
+    return ESP_OK;
+}

main/CMakeLists.txt

@@ -2,4 +2,4 @@ idf_component_register(SRCS "main.c" "project_cfg.c" "player.c" "audio_ring.c" "
                        INCLUDE_DIRS "."
                        REQUIRES esp_app_format esp_hw_support heap esp_http_client mbedtls esp_timer
                                 aes67_board aes67_health aes67_net aes67_ota aes67_ptp aes67_sdp_sap
-                                aes67_syslog aes67_tx aes67_web)
+                                aes67_syslog aes67_tx aes67_web spotify)

main/player.c

@@ -8,6 +8,7 @@
 #include "audio_ring.h"
 #include "decoder.h"
 #include "hls.h"
+#include "spotify.h"
 #include "esp_log.h"
 #include "freertos/FreeRTOS.h"
 #include "freertos/task.h"
@@ -118,7 +119,10 @@ esp_err_t player_init(void)
     if (err != ESP_OK) {
         return err;
     }
-    err = hls_start(decoder_feed);
+    cJSON *sc = cfg_get("source");
+    spotify_init(cJSON_GetObjectItemCaseSensitive(sc, "spotify_name")->valuestring);
+    cJSON_Delete(sc);
+        err = hls_start(decoder_feed);
     if (err != ESP_OK) {
         return err;
     }

sdkconfig.defaults

@@ -28,3 +28,6 @@ CONFIG_LWIP_MAX_SOCKETS=16
 # 32 MB PSRAM in the P4 package (hex mode, 200 MHz; 250 MHz needs rev >= 3). Needed for step 7:
 # HLS segment buffers, cspot, decoders. malloc() puts blocks >16 KB in PSRAM; DMA buffers stay internal.
 CONFIG_SPIRAM=y
+
+# cspot (Spotify Connect, step 7.5) needs C++ exceptions.
+CONFIG_COMPILER_CXX_EXCEPTIONS=y