diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index 327ea86..d81a9c5 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -182,6 +182,15 @@ config USB_FUNCTION_THOR
 	  Enable Tizen's THOR download protocol support in U-Boot. It
 	  allows downloading images into memory and flash them to target device.
 
+config USB_FUNCTION_ACM
+	bool "Enable CDC ACM gadget"
+	select SYS_STDIO_DEREGISTER
+	select CIRCBUF
+	help
+	  ACM serial link. This function can be used to create a stdio device to
+	  interoperate with MS-Windows hosts or with the Linux-USB "cdc-acm"
+	  driver.
+
 endif # USB_GADGET_DOWNLOAD
 
 config USB_ETHER
diff --git a/drivers/usb/gadget/Makefile b/drivers/usb/gadget/Makefile
index f560068..d5d891b 100644
--- a/drivers/usb/gadget/Makefile
+++ b/drivers/usb/gadget/Makefile
@@ -30,6 +30,7 @@ obj-$(CONFIG_USB_FUNCTION_MASS_STORAGE) += f_mass_storage.o
 obj-$(CONFIG_USB_FUNCTION_FASTBOOT) += f_fastboot.o
 obj-$(CONFIG_USB_FUNCTION_SDP) += f_sdp.o
 obj-$(CONFIG_USB_FUNCTION_ROCKUSB) += f_rockusb.o
+obj-$(CONFIG_USB_FUNCTION_ACM)	+= f_acm.o
 endif
 endif
 ifdef CONFIG_USB_ETHER
diff --git a/drivers/usb/gadget/f_acm.c b/drivers/usb/gadget/f_acm.c
new file mode 100644
index 0000000..5115f1d
--- /dev/null
+++ b/drivers/usb/gadget/f_acm.c
@@ -0,0 +1,663 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * USB CDC serial (ACM) function driver
+ *
+ * Copyright (C) 2003 Al Borchers (alborchers@steinerpoint.com)
+ * Copyright (C) 2008 by David Brownell
+ * Copyright (C) 2008 by Nokia Corporation
+ * Copyright (C) 2009 by Samsung Electronics
+ * Copyright (c) 2021, Linaro Ltd <loic.poulain@linaro.org>
+ */
+
+#include <circbuf.h>
+#include <common.h>
+#include <console.h>
+#include <errno.h>
+#include <g_dnl.h>
+#include <malloc.h>
+#include <memalign.h>
+#include <stdio_dev.h>
+#include <version.h>
+#include <watchdog.h>
+
+#include <linux/usb/ch9.h>
+#include <linux/usb/gadget.h>
+#include <linux/usb/composite.h>
+#include <linux/usb/cdc.h>
+
+#define REQ_SIZE_MAX	512
+
+struct f_acm {
+	int ctrl_id;
+	int data_id;
+
+	struct usb_ep *ep_in;
+	struct usb_ep *ep_out;
+	struct usb_ep *ep_notify;
+
+	struct usb_request *req_in;
+	struct usb_request *req_out;
+
+	bool connected;
+	bool tx_on;
+
+	circbuf_t rx_buf;
+	circbuf_t tx_buf;
+
+	struct stdio_dev stdio;
+	struct usb_function usb_function;
+
+	struct usb_cdc_line_coding line_coding;
+	u16 handshake_bits;
+#define ACM_CTRL_RTS	BIT(1)	/* unused with full duplex */
+#define ACM_CTRL_DTR	BIT(0)	/* host is ready for data r/w */
+
+	int controller_index;
+};
+
+static inline struct f_acm *func_to_acm(struct usb_function *f)
+{
+	return container_of(f, struct f_acm, usb_function);
+}
+
+static inline struct f_acm *stdio_to_acm(struct stdio_dev *s)
+{
+	/* stdio dev is cloned on registration, do not use container_of */
+	return s->priv;
+}
+
+static struct usb_interface_assoc_descriptor
+acm_iad_descriptor = {
+	.bLength =              sizeof(acm_iad_descriptor),
+	.bDescriptorType =      USB_DT_INTERFACE_ASSOCIATION,
+	.bFirstInterface =      0,
+	.bInterfaceCount =      2,	// control + data
+	.bFunctionClass =       USB_CLASS_COMM,
+	.bFunctionSubClass =    USB_CDC_SUBCLASS_ACM,
+	.bFunctionProtocol =    USB_CDC_ACM_PROTO_AT_V25TER,
+};
+
+static struct usb_interface_descriptor acm_control_intf_desc = {
+	.bLength =              USB_DT_INTERFACE_SIZE,
+	.bDescriptorType =      USB_DT_INTERFACE,
+	.bNumEndpoints =        1,
+	.bInterfaceClass =      USB_CLASS_COMM,
+	.bInterfaceSubClass =   USB_CDC_SUBCLASS_ACM,
+	.bInterfaceProtocol =   USB_CDC_ACM_PROTO_AT_V25TER,
+};
+
+static struct usb_interface_descriptor acm_data_intf_desc = {
+	.bLength =              sizeof(acm_data_intf_desc),
+	.bDescriptorType =      USB_DT_INTERFACE,
+	.bNumEndpoints =        2,
+	.bInterfaceClass =      USB_CLASS_CDC_DATA,
+};
+
+static struct usb_cdc_header_desc acm_header_desc = {
+	.bLength =		sizeof(acm_header_desc),
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubType =	USB_CDC_HEADER_TYPE,
+	.bcdCDC =		cpu_to_le16(0x0110),
+};
+
+static struct usb_cdc_call_mgmt_descriptor acm_call_mgmt_desc = {
+	.bLength =              sizeof(acm_call_mgmt_desc),
+	.bDescriptorType =      USB_DT_CS_INTERFACE,
+	.bDescriptorSubType =   USB_CDC_CALL_MANAGEMENT_TYPE,
+	.bmCapabilities =       0,
+	.bDataInterface =       0x01,
+};
+
+static struct usb_cdc_acm_descriptor acm_desc = {
+	.bLength =		sizeof(acm_desc),
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubType =	USB_CDC_ACM_TYPE,
+	.bmCapabilities =	USB_CDC_CAP_LINE,
+};
+
+static struct usb_cdc_union_desc acm_union_desc = {
+	.bLength =		sizeof(acm_union_desc),
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubType =	USB_CDC_UNION_TYPE,
+	.bMasterInterface0 =	0x00,
+	.bSlaveInterface0 =	0x01,
+};
+
+static struct usb_endpoint_descriptor acm_fs_notify_desc = {
+	.bLength =              USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType =      USB_DT_ENDPOINT,
+	.bEndpointAddress =     3 | USB_DIR_IN,
+	.bmAttributes =         USB_ENDPOINT_XFER_INT,
+	.wMaxPacketSize =       cpu_to_le16(64),
+	.bInterval =            32,
+};
+
+static struct usb_endpoint_descriptor acm_fs_in_desc = {
+	.bLength =              USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType =      USB_DT_ENDPOINT,
+	.bEndpointAddress =     USB_DIR_IN,
+	.bmAttributes =         USB_ENDPOINT_XFER_BULK,
+};
+
+static struct usb_endpoint_descriptor acm_fs_out_desc = {
+	.bLength =              USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType =      USB_DT_ENDPOINT,
+	.bEndpointAddress =     USB_DIR_OUT,
+	.bmAttributes =         USB_ENDPOINT_XFER_BULK,
+};
+
+static struct usb_descriptor_header *acm_fs_function[] = {
+	(struct usb_descriptor_header *)&acm_iad_descriptor,
+	(struct usb_descriptor_header *)&acm_control_intf_desc,
+	(struct usb_descriptor_header *)&acm_header_desc,
+	(struct usb_descriptor_header *)&acm_call_mgmt_desc,
+	(struct usb_descriptor_header *)&acm_desc,
+	(struct usb_descriptor_header *)&acm_union_desc,
+	(struct usb_descriptor_header *)&acm_fs_notify_desc,
+	(struct usb_descriptor_header *)&acm_data_intf_desc,
+	(struct usb_descriptor_header *)&acm_fs_in_desc,
+	(struct usb_descriptor_header *)&acm_fs_out_desc,
+	NULL,
+};
+
+static struct usb_endpoint_descriptor acm_hs_notify_desc = {
+	.bLength =              USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType =      USB_DT_ENDPOINT,
+	.bmAttributes =         USB_ENDPOINT_XFER_INT,
+	.wMaxPacketSize =       cpu_to_le16(64),
+	.bInterval =            11,
+};
+
+static struct usb_endpoint_descriptor acm_hs_in_desc = {
+	.bLength		= USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType	= USB_DT_ENDPOINT,
+	.bmAttributes		= USB_ENDPOINT_XFER_BULK,
+	.wMaxPacketSize		= cpu_to_le16(512),
+};
+
+static struct usb_endpoint_descriptor acm_hs_out_desc = {
+	.bLength		= USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType	= USB_DT_ENDPOINT,
+	.bmAttributes		= USB_ENDPOINT_XFER_BULK,
+	.wMaxPacketSize		= cpu_to_le16(512),
+};
+
+static struct usb_descriptor_header *acm_hs_function[] = {
+	(struct usb_descriptor_header *)&acm_iad_descriptor,
+	(struct usb_descriptor_header *)&acm_control_intf_desc,
+	(struct usb_descriptor_header *)&acm_header_desc,
+	(struct usb_descriptor_header *)&acm_call_mgmt_desc,
+	(struct usb_descriptor_header *)&acm_desc,
+	(struct usb_descriptor_header *)&acm_union_desc,
+	(struct usb_descriptor_header *)&acm_hs_notify_desc,
+	(struct usb_descriptor_header *)&acm_data_intf_desc,
+	(struct usb_descriptor_header *)&acm_hs_in_desc,
+	(struct usb_descriptor_header *)&acm_hs_out_desc,
+	NULL,
+};
+
+static inline struct usb_endpoint_descriptor *
+ep_desc(struct usb_gadget *g, struct usb_endpoint_descriptor *hs,
+	struct usb_endpoint_descriptor *fs)
+{
+	if (gadget_is_dualspeed(g) && g->speed == USB_SPEED_HIGH)
+		return hs;
+	return fs;
+}
+
+static int acm_bind(struct usb_configuration *c, struct usb_function *f)
+{
+	struct usb_gadget *gadget = c->cdev->gadget;
+	struct f_acm *f_acm = func_to_acm(f);
+	struct usb_ep *ep;
+	int id;
+
+	id = usb_interface_id(c, f);
+	if (id < 0)
+		return id;
+
+	acm_iad_descriptor.bFirstInterface = id;
+	acm_control_intf_desc.bInterfaceNumber = id;
+	acm_union_desc.bMasterInterface0 = id;
+
+	f_acm->ctrl_id = id;
+
+	id = usb_interface_id(c, f);
+	if (id < 0)
+		return id;
+
+	acm_data_intf_desc.bInterfaceNumber = id;
+	acm_union_desc.bSlaveInterface0 = id;
+	acm_call_mgmt_desc.bDataInterface = id;
+
+	f_acm->data_id = id;
+
+	/* allocate instance-specific endpoints */
+	ep = usb_ep_autoconfig(gadget, &acm_fs_in_desc);
+	if (!ep)
+		return -ENODEV;
+
+	f_acm->ep_in = ep;
+
+	ep = usb_ep_autoconfig(gadget, &acm_fs_out_desc);
+	if (!ep)
+		return -ENODEV;
+
+	f_acm->ep_out = ep;
+
+	ep = usb_ep_autoconfig(gadget, &acm_fs_notify_desc);
+	if (!ep)
+		return -ENODEV;
+
+	f_acm->ep_notify = ep;
+
+	if (gadget_is_dualspeed(gadget)) {
+		/* Assume endpoint addresses are the same for both speeds */
+		acm_hs_in_desc.bEndpointAddress = acm_fs_in_desc.bEndpointAddress;
+		acm_hs_out_desc.bEndpointAddress = acm_fs_out_desc.bEndpointAddress;
+		acm_hs_notify_desc.bEndpointAddress = acm_fs_notify_desc.bEndpointAddress;
+	}
+
+	return 0;
+}
+
+static void acm_unbind(struct usb_configuration *c, struct usb_function *f)
+{
+	struct f_acm *f_acm = func_to_acm(f);
+	struct stdio_dev *stdio;
+
+	stdio = stdio_get_by_name(f_acm->stdio.name);
+	stdio_deregister_dev(stdio, 1);
+
+	buf_free(&f_acm->rx_buf);
+	buf_free(&f_acm->tx_buf);
+
+	free(f_acm);
+}
+
+static void acm_notify_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	if (req->status)
+		printf("CDC ACM notify failed (%d)\n", req->status);
+
+	/* nothing to do */
+}
+
+static void acm_tx_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	static int once; /* prevent infinite recursion */
+
+	if (req->status && !once++)
+		printf("CDC ACM TX failed (%d)\n", req->status);
+
+	struct f_acm *f_acm = req->context;
+
+	f_acm->tx_on = true;
+}
+
+static void acm_rx_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct f_acm *f_acm = req->context;
+
+	if (req->status != 0)
+		printf("CDC ACM RX failed (%d)\n", req->status);
+
+	buf_push(&f_acm->rx_buf, req->buf, req->actual);
+
+	/* Queue RX req again */
+	req->actual = 0;
+	usb_ep_queue(ep, req, 0);
+}
+
+static struct usb_request *acm_start_ep(struct usb_ep *ep, void *complete_cb,
+					void *context)
+{
+	struct usb_request *req;
+
+	req = usb_ep_alloc_request(ep, 0);
+	if (!req)
+		return NULL;
+
+	req->length = REQ_SIZE_MAX;
+	req->buf = memalign(CONFIG_SYS_CACHELINE_SIZE, REQ_SIZE_MAX);
+	if (!req->buf) {
+		usb_ep_free_request(ep, req);
+		return NULL;
+	}
+
+	memset(req->buf, 0, req->length);
+	req->complete = complete_cb;
+	req->context = context;
+
+	return req;
+}
+
+static int acm_start_data(struct f_acm *f_acm, struct usb_gadget *gadget)
+{
+	const struct usb_endpoint_descriptor *d;
+	int ret;
+
+	/* EP IN */
+	d = ep_desc(gadget, &acm_hs_in_desc, &acm_fs_in_desc);
+	ret = usb_ep_enable(f_acm->ep_in, d);
+	if (ret)
+		return ret;
+
+	f_acm->req_in = acm_start_ep(f_acm->ep_in, acm_tx_complete, f_acm);
+
+	/* EP OUT */
+	d = ep_desc(gadget, &acm_hs_out_desc, &acm_fs_out_desc);
+	ret = usb_ep_enable(f_acm->ep_out, d);
+	if (ret)
+		return ret;
+
+	f_acm->req_out = acm_start_ep(f_acm->ep_out, acm_rx_complete, f_acm);
+
+	/* Start OUT transfer (EP OUT) */
+	ret = usb_ep_queue(f_acm->ep_out, f_acm->req_out, 0);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int acm_start_ctrl(struct f_acm *f_acm, struct usb_gadget *gadget)
+{
+	const struct usb_endpoint_descriptor *d;
+
+	usb_ep_disable(f_acm->ep_notify);
+
+	d = ep_desc(gadget, &acm_hs_notify_desc, &acm_fs_notify_desc);
+	usb_ep_enable(f_acm->ep_notify, d);
+
+	acm_start_ep(f_acm->ep_notify, acm_notify_complete, f_acm);
+
+	return 0;
+}
+
+static int acm_set_alt(struct usb_function *f, unsigned int intf, unsigned int alt)
+{
+	struct usb_gadget *gadget = f->config->cdev->gadget;
+	struct f_acm *f_acm = func_to_acm(f);
+
+	if (intf == f_acm->ctrl_id) {
+		return acm_start_ctrl(f_acm, gadget);
+	} else if (intf == f_acm->data_id) {
+		acm_start_data(f_acm, gadget);
+		f_acm->connected = true;
+		f_acm->tx_on = true;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static int acm_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
+{
+	struct usb_gadget *gadget =  f->config->cdev->gadget;
+	struct usb_request *req = f->config->cdev->req;
+	u16 w_index = le16_to_cpu(ctrl->wIndex);
+	u16 w_value = le16_to_cpu(ctrl->wValue);
+	u16 w_length = le16_to_cpu(ctrl->wLength);
+	struct f_acm *f_acm = func_to_acm(f);
+	int value = -1;
+
+	switch ((ctrl->bRequestType << 8) | ctrl->bRequest) {
+	case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
+			| USB_CDC_REQ_SET_LINE_CODING:
+	{
+		/* SET_LINE_CODING */
+
+		if (w_length != sizeof(f_acm->line_coding) || w_index != f_acm->ctrl_id)
+			goto invalid;
+
+		value = w_length;
+
+		memcpy(&f_acm->line_coding, req->buf, value);
+
+		break;
+	}
+	case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
+			| USB_CDC_REQ_GET_LINE_CODING:
+	{
+		/* GET_LINE_CODING */
+
+		if (w_length != sizeof(f_acm->line_coding) || w_index != f_acm->ctrl_id)
+			goto invalid;
+
+		value = w_length;
+
+		memcpy(req->buf, &f_acm->line_coding, value);
+
+		break;
+	}
+	case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
+			| USB_CDC_REQ_SET_CONTROL_LINE_STATE:
+	{
+		/* SET_CONTROL_LINE_STATE */
+
+		if (w_index != f_acm->ctrl_id)
+			goto invalid;
+
+		value = 0;
+
+		f_acm->handshake_bits = w_value;
+
+		break;
+	}
+	default:
+invalid:
+		printf("invalid control req%02x.%02x v%04x i%04x l%d\n",
+		       ctrl->bRequestType, ctrl->bRequest, w_value, w_index,
+		       w_length);
+	}
+
+	/* respond with data transfer or status phase? */
+	if (value >= 0) {
+		req->zero = 0;
+		req->length = value;
+		usb_ep_queue(gadget->ep0, req, GFP_ATOMIC);
+	}
+
+	return 0;
+}
+
+static void acm_disable(struct usb_function *f)
+{
+	struct f_acm *f_acm = func_to_acm(f);
+
+	usb_ep_disable(f_acm->ep_out);
+	usb_ep_disable(f_acm->ep_in);
+	usb_ep_disable(f_acm->ep_notify);
+
+	if (f_acm->req_out) {
+		free(f_acm->req_out->buf);
+		usb_ep_free_request(f_acm->ep_out, f_acm->req_out);
+		f_acm->req_out = NULL;
+	}
+
+	if (f_acm->req_in) {
+		free(f_acm->req_in->buf);
+		usb_ep_free_request(f_acm->ep_in, f_acm->req_in);
+		f_acm->req_in = NULL;
+	}
+}
+
+/* static strings, in UTF-8 */
+static struct usb_string acm_string_defs[] = {
+	[0].s = "CDC Abstract Control Model (ACM)",
+	[1].s = "CDC ACM Data",
+	[2].s = "CDC Serial",
+	{  } /* end of list */
+};
+
+static struct usb_gadget_strings acm_string_table = {
+	.language = 0x0409, /* en-us */
+	.strings = acm_string_defs,
+};
+
+static struct usb_gadget_strings *acm_strings[] = {
+	&acm_string_table,
+	NULL,
+};
+
+void __acm_tx(struct f_acm *f_acm)
+{
+	int len, ret;
+
+	do {
+		usb_gadget_handle_interrupts(f_acm->controller_index);
+
+		if (!(f_acm->handshake_bits & ACM_CTRL_DTR))
+			break;
+
+		if (!f_acm->tx_on)
+			continue;
+
+		len = buf_pop(&f_acm->tx_buf, f_acm->req_in->buf, REQ_SIZE_MAX);
+		if (!len)
+			break;
+
+		f_acm->req_in->length = len;
+
+		ret = usb_ep_queue(f_acm->ep_in, f_acm->req_in, 0);
+		if (ret)
+			break;
+
+		f_acm->tx_on = false;
+
+		/* Do not reset the watchdog, if TX is stuck there is probably
+		 * a real issue.
+		 */
+	} while (1);
+}
+
+static bool acm_connected(struct stdio_dev *dev)
+{
+	struct f_acm *f_acm = stdio_to_acm(dev);
+
+	/* give a chance to process udc irq */
+	usb_gadget_handle_interrupts(f_acm->controller_index);
+
+	return f_acm->connected;
+}
+
+/* STDIO */
+static int acm_stdio_tstc(struct stdio_dev *dev)
+{
+	struct f_acm *f_acm = stdio_to_acm(dev);
+
+	usb_gadget_handle_interrupts(f_acm->controller_index);
+
+	return (f_acm->rx_buf.size > 0);
+}
+
+static int acm_stdio_getc(struct stdio_dev *dev)
+{
+	struct f_acm *f_acm = stdio_to_acm(dev);
+	char c;
+
+	/* Wait for a character to arrive. */
+	while (!acm_stdio_tstc(dev))
+		WATCHDOG_RESET();
+
+	buf_pop(&f_acm->rx_buf, &c, 1);
+
+	return c;
+}
+
+static void acm_stdio_putc(struct stdio_dev *dev, const char c)
+{
+	struct f_acm *f_acm = stdio_to_acm(dev);
+
+	buf_push(&f_acm->tx_buf, &c, 1);
+
+	if (!f_acm->connected)
+		return;
+
+	__acm_tx(f_acm);
+}
+
+static void acm_stdio_puts(struct stdio_dev *dev, const char *str)
+{
+	struct f_acm *f_acm = stdio_to_acm(dev);
+
+	buf_push(&f_acm->tx_buf, str, strlen(str));
+
+	if (!f_acm->connected)
+		return;
+
+	__acm_tx(f_acm);
+}
+
+static int acm_stdio_start(struct stdio_dev *dev)
+{
+	while (!acm_connected(dev)) {
+		if (ctrlc())
+			return -ECANCELED;
+
+		WATCHDOG_RESET();
+	}
+
+	return 0;
+}
+
+static int acm_stdio_stop(struct stdio_dev *dev)
+{
+	/* nothing to do */
+	return 0;
+}
+
+int acm_add(struct usb_configuration *c)
+{
+	struct stdio_dev *stdio;
+	struct f_acm *f_acm;
+	int status;
+
+	f_acm = calloc(1, sizeof(*f_acm));
+	if (!f_acm)
+		return -ENOMEM;
+
+	f_acm->usb_function.name = "f_acm";
+	f_acm->usb_function.bind = acm_bind;
+	f_acm->usb_function.unbind = acm_unbind;
+	f_acm->usb_function.set_alt = acm_set_alt;
+	f_acm->usb_function.disable = acm_disable;
+	f_acm->usb_function.strings = acm_strings;
+	f_acm->usb_function.descriptors = acm_fs_function;
+	f_acm->usb_function.hs_descriptors = acm_hs_function;
+	f_acm->usb_function.setup = acm_setup;
+	f_acm->controller_index = 0;
+
+	status = usb_add_function(c, &f_acm->usb_function);
+	if (status) {
+		free(f_acm);
+		return status;
+	}
+
+	stdio = &f_acm->stdio;
+
+	buf_init(&f_acm->rx_buf, 2048);
+	buf_init(&f_acm->tx_buf, 2048);
+
+	strcpy(stdio->name, "stdio_acm");
+	stdio->flags = DEV_FLAGS_INPUT | DEV_FLAGS_OUTPUT;
+	stdio->tstc = acm_stdio_tstc;
+	stdio->getc = acm_stdio_getc;
+	stdio->putc = acm_stdio_putc;
+	stdio->puts = acm_stdio_puts;
+	stdio->start = acm_stdio_start;
+	stdio->stop = acm_stdio_stop;
+	stdio->priv = f_acm;
+	stdio->ext = 0;
+
+	status = stdio_register(&f_acm->stdio);
+	if (status) {
+		buf_free(&f_acm->rx_buf);
+		buf_free(&f_acm->tx_buf);
+	}
+
+	return status;
+}
+
+DECLARE_GADGET_BIND_CALLBACK(usb_serial_acm, acm_add);
