@@ -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
@@ -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
new file mode 100644
@@ -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);
Add support for CDC ACM using the new UDC and gadget API. This protocol can be used for serial over USB data transfer and is widely supported by various OS (GNU/Linux, MS-Windows, OSX...). The usual purpose of such link is to access device debug console and can be useful for products not exposing regular UART to the user. Signed-off-by: Loic Poulain <loic.poulain@linaro.org> --- drivers/usb/gadget/Kconfig | 9 + drivers/usb/gadget/Makefile | 1 + drivers/usb/gadget/f_acm.c | 663 ++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 673 insertions(+) create mode 100644 drivers/usb/gadget/f_acm.c -- 2.7.4