zephyr: Create ability to use device_next with CDC ACM as REPL.

This enables using the newer USB stack and its CDC ACM for the REPL.

To switch to it, board file must contain `CONFIG_USB_DEVICE_STACK_NEXT=y`
and `CONFIG_USBD_CDC_ACM_CLASS=y`.  In the case of a board that is a
platform that supports the older device stack, `CONFIG_USB_DEVICE_STACK=n`
may be necessary.

Signed-off-by: Vdragon <mail@massdriver.space>

ports/zephyr/CMakeLists.txt

@@ -128,6 +128,7 @@ add_dependencies(${MICROPY_TARGET} zephyr_generated_headers)
 target_sources(app PRIVATE
     src/zephyr_start.c
     src/zephyr_getchar.c
+    src/usbd.c
 )
 
 target_link_libraries(app PRIVATE ${MICROPY_TARGET})

ports/zephyr/Kconfig

@@ -49,6 +49,14 @@ config MICROPY_FROZEN_MANIFEST
 	depends on MICROPY_FROZEN_MODULES
 	default "boards/manifest.py"
 
+config MICROPY_USB_DEVICE_VID
+	hex "USB VID"
+	default 0x2fe3
+
+config MICROPY_USB_DEVICE_PID
+	hex "USB PID"
+	default 0x0001
+
 endmenu # MicroPython Options
 
 source "Kconfig.zephyr"

ports/zephyr/main.c

@@ -63,6 +63,10 @@
 
 static char heap[MICROPY_HEAP_SIZE];
 
+#if defined(CONFIG_USB_DEVICE_STACK_NEXT)
+extern int mp_usbd_init(void);
+#endif // defined(CONFIG_USB_DEVICE_STACK_NEXT)
+
 void init_zephyr(void) {
     // We now rely on CONFIG_NET_APP_SETTINGS to set up bootstrap
     // network addresses.
@@ -143,6 +147,10 @@ soft_reset:
     usb_enable(NULL);
     #endif
 
+    #ifdef CONFIG_USB_DEVICE_STACK_NEXT
+    mp_usbd_init();
+    #endif
+
     #if MICROPY_VFS
     vfs_init();
     #endif

ports/zephyr/src/usbd.c

@@ -0,0 +1,183 @@
+/*
+* This file is part of the MicroPython project, http://micropython.org/
+*
+* The MIT License (MIT)
+*
+* Copyright (c) 2024-2025 MASSDRIVER EI (massdriver.space)
+*
+* Permission is hereby granted, free of charge, to any person obtaining a copy
+* of this software and associated documentation files (the "Software"), to deal
+* in the Software without restriction, including without limitation the rights
+* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+* copies of the Software, and to permit persons to whom the Software is
+* furnished to do so, subject to the following conditions:
+*
+* The above copyright notice and this permission notice shall be included in
+* all copies or substantial portions of the Software.
+*
+* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+* THE SOFTWARE.
+*/
+#include <stdint.h>
+
+#include <zephyr/device.h>
+#include <zephyr/usb/usbd.h>
+#include <zephyr/usb/bos.h>
+
+#if defined(CONFIG_USB_DEVICE_STACK_NEXT)
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_REGISTER(mp_usbd);
+
+/* By default, do not register the USB DFU class DFU mode instance. */
+static const char *const blocklist[] = {
+    "dfu_dfu",
+    NULL,
+};
+
+USBD_DEVICE_DEFINE(mp_usbd,
+    DEVICE_DT_GET(DT_NODELABEL(zephyr_udc0)),
+    CONFIG_MICROPY_USB_DEVICE_VID, CONFIG_MICROPY_USB_DEVICE_PID);
+
+USBD_DESC_LANG_DEFINE(mp_lang);
+USBD_DESC_MANUFACTURER_DEFINE(mp_mfr, "Zephyr Project");
+USBD_DESC_PRODUCT_DEFINE(mp_product, "Micropython on Zephyr RTOS");
+USBD_DESC_SERIAL_NUMBER_DEFINE(mp_sn);
+
+USBD_DESC_CONFIG_DEFINE(fs_cfg_desc, "FS Configuration");
+USBD_DESC_CONFIG_DEFINE(hs_cfg_desc, "HS Configuration");
+
+/* not self-powered, no remote wakeup  */
+static const uint8_t attributes = 0;
+
+/* Full speed configuration
+* power = 250 * 2 mA = 500mA
+*/
+USBD_CONFIGURATION_DEFINE(mp_fs_config,
+    attributes,
+    250, &fs_cfg_desc);
+
+/* High speed configuration */
+USBD_CONFIGURATION_DEFINE(mp_hs_config,
+    attributes,
+    250, &hs_cfg_desc);
+
+static void mp_fix_code_triple(struct usbd_context *uds_ctx,
+    const enum usbd_speed speed) {
+    /* Always use class code information from Interface Descriptors */
+    if (IS_ENABLED(CONFIG_USBD_CDC_ACM_CLASS) ||
+        IS_ENABLED(CONFIG_USBD_CDC_ECM_CLASS) ||
+        IS_ENABLED(CONFIG_USBD_CDC_NCM_CLASS) ||
+        IS_ENABLED(CONFIG_USBD_AUDIO2_CLASS)) {
+        /*
+         * Class with multiple interfaces have an Interface
+         * Association Descriptor available, use an appropriate triple
+         * to indicate it.
+         */
+        usbd_device_set_code_triple(uds_ctx, speed,
+            USB_BCC_MISCELLANEOUS, 0x02, 0x01);
+    } else {
+        usbd_device_set_code_triple(uds_ctx, speed, 0, 0, 0);
+    }
+}
+
+struct usbd_context *mp_usbd_init_device(usbd_msg_cb_t msg_cb) {
+    int err;
+
+    err = usbd_add_descriptor(&mp_usbd, &mp_lang);
+    if (err) {
+        LOG_ERR("Failed to initialize language descriptor (%d)", err);
+        return NULL;
+    }
+
+    err = usbd_add_descriptor(&mp_usbd, &mp_mfr);
+    if (err) {
+        LOG_ERR("Failed to initialize manufacturer descriptor (%d)", err);
+        return NULL;
+    }
+
+    err = usbd_add_descriptor(&mp_usbd, &mp_product);
+    if (err) {
+        LOG_ERR("Failed to initialize product descriptor (%d)", err);
+        return NULL;
+    }
+
+    err = usbd_add_descriptor(&mp_usbd, &mp_sn);
+    if (err) {
+        LOG_ERR("Failed to initialize SN descriptor (%d)", err);
+        return NULL;
+    }
+
+    if (usbd_caps_speed(&mp_usbd) == USBD_SPEED_HS) {
+        err = usbd_add_configuration(&mp_usbd, USBD_SPEED_HS,
+            &mp_hs_config);
+        if (err) {
+            LOG_ERR("Failed to add High-Speed configuration");
+            return NULL;
+        }
+
+        err = usbd_register_all_classes(&mp_usbd, USBD_SPEED_HS, 1, blocklist);
+        if (err) {
+            LOG_ERR("Failed to add register classes");
+            return NULL;
+        }
+
+        mp_fix_code_triple(&mp_usbd, USBD_SPEED_HS);
+    }
+
+    err = usbd_add_configuration(&mp_usbd, USBD_SPEED_FS,
+        &mp_fs_config);
+    if (err) {
+        LOG_ERR("Failed to add Full-Speed configuration");
+        return NULL;
+    }
+
+    err = usbd_register_all_classes(&mp_usbd, USBD_SPEED_FS, 1, blocklist);
+    if (err) {
+        LOG_ERR("Failed to add register classes");
+        return NULL;
+    }
+
+    mp_fix_code_triple(&mp_usbd, USBD_SPEED_FS);
+
+    if (msg_cb != NULL) {
+        err = usbd_msg_register_cb(&mp_usbd, msg_cb);
+        if (err) {
+            LOG_ERR("Failed to register message callback");
+            return NULL;
+        }
+    }
+
+    err = usbd_init(&mp_usbd);
+    if (err) {
+        LOG_ERR("Failed to initialize device support");
+        return NULL;
+    }
+
+    return &mp_usbd;
+}
+
+static struct usbd_context *mp_usbd_context;
+
+int mp_usbd_init(void) {
+    int err;
+
+    mp_usbd_context = mp_usbd_init_device(NULL);
+    if (mp_usbd_context == NULL) {
+        return -ENODEV;
+    }
+
+    err = usbd_enable(mp_usbd_context);
+    if (err) {
+        return err;
+    }
+
+    return 0;
+}
+
+#endif // defined(CONFIG_USB_DEVICE_STACK_NEXT)