[v3,2/2] usb: gadget: Add CDC ACM function

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.

A default stdio device named 'usbacm' is created, and can be used
to redirect console to USB link over CDC ACM:

> setenv stdin usbacm; setenv stdout usbacm

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
---
 v2: - remove possible infinite recursipe print loop
     - Remove acmconsole command, start function along the stdio device
 v3: - Use __constant_cpu_to_le16() when possible
     - Rename stdio dev to 'usbacm'
     - Rename init function to drv_usbacm_init

 common/stdio.c              |   3 +
 drivers/usb/gadget/Kconfig  |   9 +
 drivers/usb/gadget/Makefile |   1 +
 drivers/usb/gadget/f_acm.c  | 672 ++++++++++++++++++++++++++++++++++++++++++++
 include/stdio_dev.h         |   1 +
 5 files changed, 686 insertions(+)
 create mode 100644 drivers/usb/gadget/f_acm.c

On Thursday 25 November 2021 18:16:15 Loic Poulain wrote:
> 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.
> 
> A default stdio device named 'usbacm' is created, and can be used
> to redirect console to USB link over CDC ACM:
> 
> > setenv stdin usbacm; setenv stdout usbacm
> 
> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
> ---
>  v2: - remove possible infinite recursipe print loop
>      - Remove acmconsole command, start function along the stdio device
>  v3: - Use __constant_cpu_to_le16() when possible
>      - Rename stdio dev to 'usbacm'
>      - Rename init function to drv_usbacm_init

Hello! Just one question: is in this v3 patch fixed stdout-only
configuration, or it still has a bug which you described in email?
https://lore.kernel.org/u-boot/CAMZdPi8185pAiO4w2QYMtWGAFJiX=eJ_BJW1CusRE990Wr7b_w@mail.gmail.com/

Because neither in above change long nor in driver help description nor
in driver source code is any comment related to stdout-only device.

Note that stdout-only does not have to be too uncommon. For example
Nokia N900 has enabled UART, keyboard+lcd and usbtty by default and
sometimes I enabled input only from keyboard and looked at usbtty
terminal (as stdout-only) if everything is working fine (that every
pressed key on keyboard was echoed correctly back to usbtty).

> 
>  common/stdio.c              |   3 +
>  drivers/usb/gadget/Kconfig  |   9 +
>  drivers/usb/gadget/Makefile |   1 +
>  drivers/usb/gadget/f_acm.c  | 672 ++++++++++++++++++++++++++++++++++++++++++++
>  include/stdio_dev.h         |   1 +
>  5 files changed, 686 insertions(+)
>  create mode 100644 drivers/usb/gadget/f_acm.c
> 
> diff --git a/common/stdio.c b/common/stdio.c
> index 4083e4e..e07e4a4 100644
> --- a/common/stdio.c
> +++ b/common/stdio.c
> @@ -381,6 +381,9 @@ int stdio_add_devices(void)
>  #ifdef CONFIG_USB_TTY
>  	drv_usbtty_init();
>  #endif
> +#ifdef CONFIG_USB_FUNCTION_ACM
> +	drv_usbacm_init ();
> +#endif
>  	if (IS_ENABLED(CONFIG_NETCONSOLE))
>  		drv_nc_init();
>  #ifdef CONFIG_JTAG_CONSOLE
> 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..388f73d
> --- /dev/null
> +++ b/drivers/usb/gadget/f_acm.c
> @@ -0,0 +1,672 @@
> +// 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 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 struct f_acm *default_acm_function;
> +
> +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 =		__constant_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 =       __constant_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 =       __constant_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		= __constant_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		= __constant_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);
> +
> +	if (default_acm_function == f_acm)
> +		default_acm_function = NULL;
> +
> +	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)
> +{
> +	/* nothing to do */
> +}
> +
> +static void acm_tx_complete(struct usb_ep *ep, struct usb_request *req)
> +{
> +	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;
> +
> +	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,
> +};
> +
> +static 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;
> +}
> +
> +static int acm_add(struct usb_configuration *c)
> +{
> +	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;
> +	}
> +
> +	buf_init(&f_acm->rx_buf, 2048);
> +	buf_init(&f_acm->tx_buf, 2048);
> +
> +	if (!default_acm_function)
> +		default_acm_function = f_acm;
> +
> +	return status;
> +}
> +
> +DECLARE_GADGET_BIND_CALLBACK(usb_serial_acm, acm_add);
> +
> +/* 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);
> +
> +	if (c == '\n')
> +		buf_push(&f_acm->tx_buf, "\r", 1);
> +
> +	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);
> +
> +	while (*str) {
> +		if (*str == '\n')
> +			buf_push(&f_acm->tx_buf, "\r", 1);
> +
> +		buf_push(&f_acm->tx_buf, str++, 1);
> +	}
> +
> +	if (!f_acm->connected)
> +		return;
> +
> +	__acm_tx(f_acm);
> +}
> +
> +static int acm_stdio_start(struct stdio_dev *dev)
> +{
> +	int ret;
> +
> +	if (dev->priv) { /* function already exist */
> +		return 0;
> +	}
> +
> +	ret = g_dnl_register("usb_serial_acm");
> +	if (ret)
> +		return ret;
> +
> +	if (default_acm_function)
> +		dev->priv = default_acm_function;
> +	else
> +		return -ENODEV;
> +
> +	while (!acm_connected(dev)) {
> +		if (ctrlc())
> +			return -ECANCELED;
> +
> +		WATCHDOG_RESET();
> +	}
> +
> +	return 0;
> +}
> +
> +static int acm_stdio_stop(struct stdio_dev *dev)
> +{
> +	g_dnl_unregister();
> +	g_dnl_clear_detach();
> +
> +	return 0;
> +}
> +
> +int drv_usbacm_init(void)
> +{
> +	struct stdio_dev stdio;
> +
> +	strcpy(stdio.name, "usbacm");
> +	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 = NULL;
> +	stdio.ext = 0;
> +
> +	return stdio_register(&stdio);
> +}
> diff --git a/include/stdio_dev.h b/include/stdio_dev.h
> index 8fb9a12..270fa27 100644
> --- a/include/stdio_dev.h
> +++ b/include/stdio_dev.h
> @@ -103,6 +103,7 @@ int drv_lcd_init(void);
>  int drv_video_init(void);
>  int drv_keyboard_init(void);
>  int drv_usbtty_init(void);
> +int drv_usbacm_init(void);
>  int drv_nc_init(void);
>  int drv_jtag_console_init(void);
>  int cbmemc_init(void);
> -- 
> 2.7.4
>

Hi Pali,

On Thu, 25 Nov 2021 at 19:10, Pali Rohár <pali@kernel.org> wrote:
>
> On Thursday 25 November 2021 18:16:15 Loic Poulain wrote:
> > 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.
> >
> > A default stdio device named 'usbacm' is created, and can be used
> > to redirect console to USB link over CDC ACM:
> >
> > > setenv stdin usbacm; setenv stdout usbacm
> >
> > Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
> > ---
> >  v2: - remove possible infinite recursipe print loop
> >      - Remove acmconsole command, start function along the stdio device
> >  v3: - Use __constant_cpu_to_le16() when possible
> >      - Rename stdio dev to 'usbacm'
> >      - Rename init function to drv_usbacm_init
>
> Hello! Just one question: is in this v3 patch fixed stdout-only
> configuration, or it still has a bug which you described in email?
> https://lore.kernel.org/u-boot/CAMZdPi8185pAiO4w2QYMtWGAFJiX=eJ_BJW1CusRE990Wr7b_w@mail.gmail.com/
>
> Because neither in above change long nor in driver help description nor
> in driver source code is any comment related to stdout-only device.

No, actually it ended not being an issue, we can have it stdout/stdin
independently. The driver loops on 'irq'-handling to ensure the USB
controller has completely flushed TX before returning.

>
> Note that stdout-only does not have to be too uncommon. For example
> Nokia N900 has enabled UART, keyboard+lcd and usbtty by default and
> sometimes I enabled input only from keyboard and looked at usbtty
> terminal (as stdout-only) if everything is working fine (that every
> pressed key on keyboard was echoed correctly back to usbtty).

Yes, checked this case on a imx7d based board and stdout-only works as
you describe.

Regards,
Loic

On Friday 26 November 2021 09:39:18 Loic Poulain wrote:
> Hi Pali,
> 
> On Thu, 25 Nov 2021 at 19:10, Pali Rohár <pali@kernel.org> wrote:
> >
> > On Thursday 25 November 2021 18:16:15 Loic Poulain wrote:
> > > 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.
> > >
> > > A default stdio device named 'usbacm' is created, and can be used
> > > to redirect console to USB link over CDC ACM:
> > >
> > > > setenv stdin usbacm; setenv stdout usbacm
> > >
> > > Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
> > > ---
> > >  v2: - remove possible infinite recursipe print loop
> > >      - Remove acmconsole command, start function along the stdio device
> > >  v3: - Use __constant_cpu_to_le16() when possible
> > >      - Rename stdio dev to 'usbacm'
> > >      - Rename init function to drv_usbacm_init
> >
> > Hello! Just one question: is in this v3 patch fixed stdout-only
> > configuration, or it still has a bug which you described in email?
> > https://lore.kernel.org/u-boot/CAMZdPi8185pAiO4w2QYMtWGAFJiX=eJ_BJW1CusRE990Wr7b_w@mail.gmail.com/
> >
> > Because neither in above change long nor in driver help description nor
> > in driver source code is any comment related to stdout-only device.
> 
> No, actually it ended not being an issue, we can have it stdout/stdin
> independently. The driver loops on 'irq'-handling to ensure the USB
> controller has completely flushed TX before returning.

This is probably suboptimal, but important is that there is no such
issue. So it means that this new code can be replacement for old usbtty,
which is really nice!!

> >
> > Note that stdout-only does not have to be too uncommon. For example
> > Nokia N900 has enabled UART, keyboard+lcd and usbtty by default and
> > sometimes I enabled input only from keyboard and looked at usbtty
> > terminal (as stdout-only) if everything is working fine (that every
> > pressed key on keyboard was echoed correctly back to usbtty).
> 
> Yes, checked this case on a imx7d based board and stdout-only works as
> you describe.
> 
> Regards,
> Loic