USB Device next cdc acm can get in a deadlock when the host doesn't pull the endpoint data

samples/subsys/usb/passthrough_irq_usb/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(passthrough)
+
+include(${ZEPHYR_BASE}/samples/subsys/usb/common/common.cmake)
+target_sources(app PRIVATE src/main.c)

samples/subsys/usb/passthrough_irq_usb/Kconfig

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+# Copyright (c) 2023 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+# Source common USB sample options used to initialize new experimental USB
+# device stack. The scope of these options is limited to USB samples in project
+# tree, you cannot use them in your own application.
+source "samples/subsys/usb/common/Kconfig.sample_usbd"
+
+source "Kconfig.zephyr"

samples/subsys/usb/passthrough_irq_usb/README.rst

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+.. zephyr:code-sample:: passthrough_irq_usb
+   :name: USB-UART Passthrough
+   :relevant-api: uart_interface
+
+   Pass data directly between the console and another UART interface.
+
+Overview
+********
+
+This sample will connect a physical UART interfaces to a USB uart, as if Zephyr
+and the processor were not present. Data read from the console is transmitted
+to the "*other*" interface, and data read from the "*other*" interface is
+relayed to the console.
+
+The source code for this sample application can be found at:
+:zephyr_file:`samples/subsys/usb/passthrough_irq_usb`.
+
+Requirements
+************
+
+#. One USB UART interface, identified as Zephyr's first usb acm interface.
+#. A second UART connected to something interesting (e.g: GPS), identified as
+   the chosen ``uart,passthrough`` device - the pins and baudrate will need to
+   be configured correctly.
+
+Building and Running
+********************
+
+Build and flash the sample as follows, changing ``nucleo_l476rg`` for your
+board:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/drivers/uart/passthrough
+   :board: nucleo_l476rg
+   :goals: build flash
+   :compact:
+
+Sample Output
+=============
+
+.. code-block:: console
+
+    *** Booting Zephyr OS build zephyr-v3.5.0-2988-gb84bab36b941 ***
+    Console Device: 0x8003940
+    Other Device:   0x800392c
+    $GNGSA,A,3,31,29,25,26,,,,,,,,,11.15,10.66,3.29,1*06
+    $GNGSA,A,3,,,,,,,,,,,,,11.15,10.66,3.29,2*0F
+    $GNGSA,A,3,,,,,,,,,,,,,11.15,10.66,3.29,3*0E
+    $GNGSA,A,3,,,,,,,,,,,,,11.15,10.66,3.29,4*09
+    $GNGSA,A,3,,,,,,,,,,,,,11.15,10.66,3.29,5*08

samples/subsys/usb/passthrough_irq_usb/app.overlay

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+/*
+ * Copyright (c) 2021 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&zephyr_udc0 {
+	cdc_acm_uart0 {
+		compatible = "zephyr,cdc-acm-uart";
+	};
+};

samples/subsys/usb/passthrough_irq_usb/prj.conf

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+CONFIG_SERIAL=y
+CONFIG_RING_BUFFER=y
+CONFIG_UART_INTERRUPT_DRIVEN=y
+
+CONFIG_USB_DEVICE_STACK_NEXT=y
+CONFIG_USBD_CDC_ACM_CLASS=y
+
+CONFIG_SAMPLE_USBD_PID=0x0001
+CONFIG_SAMPLE_USBD_PRODUCT="USBD CDC ACM sample"

samples/subsys/usb/passthrough_irq_usb/sample.yml

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+sample:
+  name: USB-UART Passthrough
+tests:
+  sample.drivers.uart:
+    tags:
+      - serial
+      - uart
+      - usb
+    filter: CONFIG_SERIAL and
+            CONFIG_UART_INTERRUPT_DRIVEN and
+            dt_chosen_enabled("uart,passthrough")
+    harness: keyboard

samples/subsys/usb/passthrough_irq_usb/src/main.c

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+/*
+ * Copyright (c) 2024 Argentum Systems Ltd.
+ * Copyright (c) 2024 SynchronicIT BV
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+#include <zephyr/device.h>
+#include <zephyr/drivers/uart.h>
+#include <zephyr/sys/ring_buffer.h>
+
+#include <stdio.h>
+#include <string.h>
+
+
+#include <zephyr/usb/usb_device.h>
+#include <zephyr/usb/usbd.h>
+#include <zephyr/logging/log.h>
+LOG_MODULE_REGISTER(passthrough, LOG_LEVEL_INF);
+
+
+const struct device *const usb_dev = DEVICE_DT_GET(DT_NODELABEL(cdc_acm_uart0));
+const struct device *const uart_dev = DEVICE_DT_GET(DT_CHOSEN(uart_passthrough));
+
+#define RING_BUF_SIZE 1024
+
+uint8_t ring_buffer[2][RING_BUF_SIZE];
+
+struct ring_buf usb_ringbuf;
+struct ring_buf uart_ringbuf;
+
+static inline void print_baudrate(const struct device *dev)
+{
+	uint32_t baudrate;
+	int ret;
+
+	ret = uart_line_ctrl_get(dev, UART_LINE_CTRL_BAUD_RATE, &baudrate);
+	if (ret) {
+		LOG_WRN("Failed to get baudrate, ret code %d", ret);
+	} else {
+		LOG_INF("Baudrate %u", baudrate);
+	}
+}
+
+#if defined(CONFIG_USB_DEVICE_STACK_NEXT)
+static struct usbd_context *sample_usbd;
+K_SEM_DEFINE(dtr_sem, 0, 1);
+
+static void sample_msg_cb(struct usbd_context *const ctx, const struct usbd_msg *msg)
+{
+	LOG_INF("USBD message: %s", usbd_msg_type_string(msg->type));
+
+	if (usbd_can_detect_vbus(ctx)) {
+		if (msg->type == USBD_MSG_VBUS_READY) {
+			if (usbd_enable(ctx)) {
+				LOG_ERR("Failed to enable device support");
+			}
+		}
+
+		if (msg->type == USBD_MSG_VBUS_REMOVED) {
+			if (usbd_disable(ctx)) {
+				LOG_ERR("Failed to disable device support");
+			}
+		}
+	}
+
+	if (msg->type == USBD_MSG_CDC_ACM_CONTROL_LINE_STATE) {
+		uint32_t dtr = 0U;
+
+		uart_line_ctrl_get(msg->dev, UART_LINE_CTRL_DTR, &dtr);
+		if (dtr) {
+			k_sem_give(&dtr_sem);
+		}
+	}
+
+	if (msg->type == USBD_MSG_CDC_ACM_LINE_CODING) {
+		print_baudrate(msg->dev);
+	}
+}
+
+static int enable_usb_device_next(void)
+{
+	int err;
+
+	sample_usbd = sample_usbd_init_device(sample_msg_cb);
+	if (sample_usbd == NULL) {
+		LOG_ERR("Failed to initialize USB device");
+		return -ENODEV;
+	}
+
+	if (!usbd_can_detect_vbus(sample_usbd)) {
+		err = usbd_enable(sample_usbd);
+		if (err) {
+			LOG_ERR("Failed to enable device support");
+			return err;
+		}
+	}
+
+	LOG_INF("USB device support enabled");
+
+	return 0;
+}
+#endif /* defined(CONFIG_USB_DEVICE_STACK_NEXT) */
+
+
+static void interrupt_handler(const struct device *dev, void *user_data)
+{
+
+	struct ring_buf *ringbuf_rx; 
+	struct ring_buf *ringbuf_tx;
+	const struct device *peer = user_data;
+
+	if(dev == usb_dev) {
+		ringbuf_rx = &uart_ringbuf;
+		ringbuf_tx = &usb_ringbuf;
+
+	} else {
+		ringbuf_rx = &usb_ringbuf;
+		ringbuf_tx = &uart_ringbuf;
+	}
+
+	while (uart_irq_update(dev) && uart_irq_is_pending(dev)) {
+		if (uart_irq_rx_ready(dev)) {
+			int recv_len, rb_len;
+			uint8_t buffer[64];
+			size_t len = MIN(ring_buf_space_get(ringbuf_rx), sizeof(buffer));
+
+			if (len == 0) {
+				ring_buf_get(ringbuf_rx, NULL, buffer);
+				len = MIN(ring_buf_space_get(ringbuf_rx), sizeof(buffer));
+			}
+
+			recv_len = uart_fifo_read(dev, buffer, len);
+			if (recv_len < 0) {
+				LOG_ERR("Failed to read UART FIFO");
+				recv_len = 0;
+			};
+
+			rb_len = ring_buf_put(ringbuf_rx, buffer, recv_len);
+			if (rb_len < recv_len) {
+				LOG_ERR("Drop %u bytes", recv_len - rb_len);
+			}
+
+			LOG_DBG("tty fifo -> ringbuf %d bytes", rb_len);
+			if (rb_len) {
+				uart_irq_tx_enable(peer);
+			}
+		}
+
+		if (uart_irq_tx_ready(dev)) {
+			uint8_t buffer[64];
+			int rb_len, send_len;
+
+			rb_len = ring_buf_get(ringbuf_tx, buffer, sizeof(buffer));
+			if (!rb_len) {
+				LOG_DBG("Ring buffer empty, disable TX IRQ");
+				uart_irq_tx_disable(dev);
+				continue;
+			}
+
+			send_len = uart_fifo_fill(dev, buffer, rb_len);
+			if (send_len < rb_len) {
+				LOG_ERR("Drop %d bytes", rb_len - send_len);
+			}
+
+			LOG_DBG("ringbuf -> tty fifo %d bytes", send_len);
+		}
+	}
+}
+
+int main(void)
+{
+	int ret;
+
+	if (!device_is_ready(uart_dev)) {
+		LOG_ERR("UART device not ready");
+		return 0;
+	}
+
+	if (!device_is_ready(usb_dev)) {
+		LOG_ERR("CDC ACM device not ready");
+		return 0;
+	}
+
+#if defined(CONFIG_USB_DEVICE_STACK_NEXT)
+		ret = enable_usb_device_next();
+#else
+		ret = usb_enable(NULL);
+#endif
+
+	if (ret != 0) {
+		LOG_ERR("Failed to enable USB");
+		return 0;
+	}
+
+	ring_buf_init(&uart_ringbuf, sizeof(ring_buffer[0]), ring_buffer[0]);
+	ring_buf_init(&usb_ringbuf, sizeof(ring_buffer[1]), ring_buffer[1]);
+
+	printk("UART Device: %p\n", uart_dev);
+	printk("USB Device:   %p\n", usb_dev);
+
+	uart_irq_callback_user_data_set(uart_dev, interrupt_handler, usb_dev);
+	uart_irq_callback_user_data_set(usb_dev, interrupt_handler, uart_dev);
+
+	/* Enable rx interrupts */
+	uart_irq_rx_enable(uart_dev);
+	uart_irq_rx_enable(usb_dev);
+
+	for (;;) {
+		k_msleep(1000);
+	}
+
+	return 0;
+}