enable gdb build flag

how to:
(1) idf.py menuconfig -> Component config -> debug config -> usb gdb mode
(2) rm -r build ; idf.py app-flash
(3) OPENOCD_COMMANDS="-f board/esp32s3-builtin.cfg" idf.py openocd
(4) (in another terminal) idf.py gdb

components/st3m/Kconfig

+menu "debug config"
+    choice DEBUG_GDB
+        prompt "gdb or tinyusb/mass storage"
+        default DEBUG_GDB_DISABLED
+        config DEBUG_GDB_DISABLED
+            bool "tinyusb/mass storage mode, no gdb"
+        config DEBUG_GDB_ENABLED
+            bool "usb gdb mode, no tinyusb/mass storage"
+    endchoice
+endmenu

components/st3m/st3m_usb.c

 #include "st3m_usb.h"
+#ifndef CONFIG_DEBUG_GDB_ENABLED
+#ifndef CONFIG_DEBUG_GDB_DISABLED
+#error "st3m: no debug flags"
+#endif
+#endif
+#ifdef CONFIG_DEBUG_GDB_ENABLED
+#ifdef CONFIG_DEBUG_GDB_DISABLED
+#error "st3m: invalid debug flags"
+#endif
+#endif
 
 static const char *TAG = "st3m-usb";
 
@@ -11,6 +21,8 @@ static const char *TAG = "st3m-usb";
 #include "esp_private/usb_phy.h"
 #include "tusb.h"
 
+#include "st3m_console.h"
+
 static SemaphoreHandle_t _mu = NULL;
 static st3m_usb_mode_kind_t _mode = st3m_usb_mode_kind_disabled;
 static usb_phy_handle_t phy_hdl;
@@ -45,12 +57,16 @@ static void _generate_serial(void) {
 }
 
 void st3m_usb_init(void) {
+#ifdef CONFIG_DEBUG_GDB_ENABLED
+    return;
+#endif
     assert(_mu == NULL);
     _mu = xSemaphoreCreateMutex();
     assert(_mu != NULL);
     _mode = st3m_usb_mode_kind_disabled;
 
     _generate_serial();
+#ifndef CONFIG_DEBUG_GDB_ENABLED
     st3m_usb_cdc_init();
     usb_phy_config_t phy_conf = {
         .controller = USB_PHY_CTRL_OTG,
@@ -68,9 +84,13 @@ void st3m_usb_init(void) {
 
     xTaskCreate(_usb_task, "usb", 4096, NULL, 5, NULL);
     ESP_LOGI(TAG, "USB stack started");
+#endif
 }
 
 void st3m_usb_mode_switch(st3m_usb_mode_t *mode) {
+#ifdef CONFIG_DEBUG_GDB_ENABLED
+    return;
+#endif
     xSemaphoreTake(_mu, portMAX_DELAY);
 
     bool running = false;
@@ -120,6 +140,9 @@ void st3m_usb_mode_switch(st3m_usb_mode_t *mode) {
 }
 
 bool st3m_usb_connected(void) {
+#ifdef CONFIG_DEBUG_GDB_ENABLED
+    return false;
+#endif
     xSemaphoreTake(_mu, portMAX_DELAY);
     bool res = _connected;
     xSemaphoreGive(_mu);
@@ -144,3 +167,24 @@ void tud_suspend_cb(bool remote_wakeup_en) {
         st3m_usb_cdc_detached();
     }
 }
+
+void st3m_usb_startup() {
+#ifdef CONFIG_DEBUG_GDB_ENABLED
+    return;
+#endif
+    st3m_usb_app_conf_t app = {
+        .fn_rx = st3m_console_cdc_on_rx,
+        .fn_txpoll = st3m_console_cdc_on_txpoll,
+        .fn_detach = st3m_console_cdc_on_detach,
+    };
+    st3m_usb_mode_t usb_mode = {
+        .kind = st3m_usb_mode_kind_app,
+        .app = &app,
+    };
+    st3m_usb_mode_switch(&usb_mode);
+    puts(" ___ _           ___     _         _");
+    puts("|  _| |___ _ _ _|_  |___| |_ ___ _| |___ ___");
+    puts("|  _| | . | | | |_  |  _| . | .'| . | . | -_|");
+    puts("|_| |_|___|_____|___|_| |___|__,|___|_  |___|");
+    puts("                                    |___|");
+}

components/st3m/st3m_usb.h

@@ -38,6 +38,7 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
+#include "sdkconfig.h"
 
 typedef enum {
     // Device should not enumerate.
@@ -106,6 +107,8 @@ void st3m_usb_mode_switch(st3m_usb_mode_t *target);
 // Initialize the subsystem. Must be called, bad things will happen otherwise.
 void st3m_usb_init();
 
+void st3m_usb_startup();
+
 // Return true if the badge is connected to a host.
 bool st3m_usb_connected(void);
 

main/main.c

@@ -57,21 +57,7 @@ static QueueHandle_t _core1_init_done_q;
 void _init_core1(void *unused) {
     st3m_usb_init();
     st3m_console_init();
-    st3m_usb_app_conf_t app = {
-        .fn_rx = st3m_console_cdc_on_rx,
-        .fn_txpoll = st3m_console_cdc_on_txpoll,
-        .fn_detach = st3m_console_cdc_on_detach,
-    };
-    st3m_usb_mode_t usb_mode = {
-        .kind = st3m_usb_mode_kind_app,
-        .app = &app,
-    };
-    st3m_usb_mode_switch(&usb_mode);
-    puts(" ___ _           ___     _         _");
-    puts("|  _| |___ _ _ _|_  |___| |_ ___ _| |___ ___");
-    puts("|  _| | . | | | |_  |  _| . | .'| . | . | -_|");
-    puts("|_| |_|___|_____|___|_| |___|__,|___|_  |___|");
-    puts("                                    |___|");
+    st3m_usb_startup();
 
     // Load bearing delay. USB crashes otherwise?
     // TODO(q3k): debug this