android_kernel_samsung_sm8650_ksu/drivers/usb/gadget/function/f_cdev.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2011, 2013-2021, The Linux Foundation. All rights reserved.
 * Linux Foundation chooses to take subject only to the GPLv2 license terms,
 * and distributes only under these terms.
 * Copyright (c) 2022-2024 Qualcomm Innovation Center, Inc. All rights reserved.
 *
 * This code also borrows from drivers/usb/gadget/u_serial.c, which is
 * Copyright (C) 2000 - 2003 Al Borchers ([email protected])
 * Copyright (C) 2008 David Brownell
 * Copyright (C) 2008 by Nokia Corporation
 * Copyright (C) 1999 - 2002 Greg Kroah-Hartman ([email protected])
 * Copyright (C) 2000 Peter Berger ([email protected])
 *
 * f_cdev_read() API implementation is using borrowed code from
 * drivers/usb/gadget/legacy/printer.c, which is
 * Copyright (C) 2003-2005 David Brownell
 * Copyright (C) 2006 Craig W. Nadler
 */

#ifdef pr_fmt
#undef pr_fmt
#endif
#define pr_fmt(fmt) "%s: " fmt, __func__

#include <linux/wait.h>
#include <linux/poll.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/debugfs.h>
#include <linux/cdev.h>
#include <linux/spinlock.h>
#include <linux/usb/gadget.h>
#include <linux/usb/cdc.h>
#include <linux/usb/composite.h>
#include <linux/module.h>
#include <asm/ioctls.h>
#include <asm-generic/termios.h>

#define DEVICE_NAME "at_usb"
#define MODULE_NAME "msm_usb_bridge"
#define NUM_INSTANCE 4

#define MAX_CDEV_INST_NAME	15
#define MAX_CDEV_FUNC_NAME	5

#define BRIDGE_RX_QUEUE_SIZE	8
#define BRIDGE_RX_BUF_SIZE	2048
#define BRIDGE_TX_QUEUE_SIZE	8
#define BRIDGE_TX_BUF_SIZE	2048

#define GS_LOG2_NOTIFY_INTERVAL		5  /* 1 << 5 == 32 msec */
#define GS_NOTIFY_MAXPACKET		10 /* notification + 2 bytes */

struct cserial {
	struct usb_function		func;
	struct usb_ep			*in;
	struct usb_ep			*out;
	struct usb_ep			*notify;
	struct usb_request		*notify_req;
	struct usb_cdc_line_coding	port_line_coding;
	u8				pending;
	u8				q_again;
	u8				data_id;
	u16				serial_state;
	u16				port_handshake_bits;
	/* control signal callbacks*/
	unsigned int (*get_dtr)(struct cserial *p);
	unsigned int (*get_rts)(struct cserial *p);

	/* notification callbacks */
	void (*connect)(struct cserial *p);
	void (*disconnect)(struct cserial *p);
	int (*send_break)(struct cserial *p, int duration);
	unsigned int (*send_carrier_detect)(struct cserial *p,
						unsigned int val);
	unsigned int (*send_ring_indicator)(struct cserial *p,
						unsigned int val);
	int (*send_modem_ctrl_bits)(struct cserial *p, int ctrl_bits);

	/* notification changes to modem */
	void (*notify_modem)(void *port, int ctrl_bits);
};

struct f_cdev {
	struct cdev		fcdev_cdev;
	struct device		dev;
	unsigned int		port_num;
	char			name[sizeof(DEVICE_NAME) + 2];
	int			minor;

	spinlock_t		port_lock;

	wait_queue_head_t	open_wq;
	wait_queue_head_t	read_wq;

	struct list_head	read_pool;
	struct list_head	read_queued;
	struct list_head	write_pool;

	/* current active USB RX request */
	struct usb_request	*current_rx_req;
	/* number of pending bytes */
	size_t			pending_rx_bytes;
	/* current USB RX buffer */
	u8			*current_rx_buf;

	/* function suspend status */
	bool			func_is_suspended;
	bool			func_wakeup_allowed;

	struct cserial		port_usb;

#define ACM_CTRL_DTR		0x01
#define ACM_CTRL_RTS		0x02
#define ACM_CTRL_DCD		0x01
#define ACM_CTRL_DSR		0x02
#define ACM_CTRL_BRK		0x04
#define ACM_CTRL_RI		0x08

	unsigned int		cbits_to_modem;
	bool			cbits_updated;

	struct workqueue_struct *fcdev_wq;
	bool			is_connected;
	bool			port_open;

	unsigned long           nbytes_from_host;
	unsigned long		nbytes_to_host;
	unsigned long           nbytes_to_port_bridge;
	unsigned long		nbytes_from_port_bridge;

	struct dentry		*debugfs_root;

	/* To test remote wakeup using debugfs */
	u8 debugfs_rw_enable;
};

struct f_cdev_opts {
	struct usb_function_instance func_inst;
	struct f_cdev *port;
	char *func_name;
	u8 port_num;
	u8 proto;
};

static int major, minors;
struct class *fcdev_classp;
static DEFINE_IDA(chardev_ida);
static DEFINE_MUTEX(chardev_ida_lock);

static int usb_cser_alloc_chardev_region(void);
static void usb_cser_chardev_deinit(void);
static void usb_cser_read_complete(struct usb_ep *ep, struct usb_request *req);
static int usb_cser_connect(struct f_cdev *port);
static void usb_cser_disconnect(struct f_cdev *port);
static struct f_cdev *f_cdev_alloc(char *func_name, int portno);
static void usb_cser_free_req(struct usb_ep *ep, struct usb_request *req);
static void usb_cser_debugfs_exit(struct f_cdev *port);

static struct usb_interface_descriptor cser_interface_desc = {
	.bLength =		USB_DT_INTERFACE_SIZE,
	.bDescriptorType =	USB_DT_INTERFACE,
	/* .bInterfaceNumber = DYNAMIC */
	.bNumEndpoints =	3,
	.bInterfaceClass =	USB_CLASS_VENDOR_SPEC,
	.bInterfaceSubClass =	USB_SUBCLASS_VENDOR_SPEC,
	/* .bInterfaceProtocol = DYNAMIC */
	/* .iInterface = DYNAMIC */
};

static struct usb_cdc_header_desc cser_header_desc  = {
	.bLength =		sizeof(cser_header_desc),
	.bDescriptorType =	USB_DT_CS_INTERFACE,
	.bDescriptorSubType =	USB_CDC_HEADER_TYPE,
	.bcdCDC =		cpu_to_le16(0x0110),
};

static struct usb_cdc_call_mgmt_descriptor
cser_call_mgmt_descriptor  = {
	.bLength =		sizeof(cser_call_mgmt_descriptor),
	.bDescriptorType =	USB_DT_CS_INTERFACE,
	.bDescriptorSubType =	USB_CDC_CALL_MANAGEMENT_TYPE,
	.bmCapabilities =	0,
	/* .bDataInterface = DYNAMIC */
};

static struct usb_cdc_acm_descriptor cser_descriptor  = {
	.bLength =		sizeof(cser_descriptor),
	.bDescriptorType =	USB_DT_CS_INTERFACE,
	.bDescriptorSubType =	USB_CDC_ACM_TYPE,
	.bmCapabilities =	USB_CDC_CAP_LINE,
};

static struct usb_cdc_union_desc cser_union_desc  = {
	.bLength =		sizeof(cser_union_desc),
	.bDescriptorType =	USB_DT_CS_INTERFACE,
	.bDescriptorSubType =	USB_CDC_UNION_TYPE,
	/* .bMasterInterface0 =	DYNAMIC */
	/* .bSlaveInterface0 =	DYNAMIC */
};

/* full speed support: */
static struct usb_endpoint_descriptor cser_fs_notify_desc = {
	.bLength =		USB_DT_ENDPOINT_SIZE,
	.bDescriptorType =	USB_DT_ENDPOINT,
	.bEndpointAddress =	USB_DIR_IN,
	.bmAttributes =		USB_ENDPOINT_XFER_INT,
	.wMaxPacketSize =	cpu_to_le16(GS_NOTIFY_MAXPACKET),
	.bInterval =		1 << GS_LOG2_NOTIFY_INTERVAL,
};

static struct usb_endpoint_descriptor cser_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 cser_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 *cser_fs_function[] = {
	(struct usb_descriptor_header *) &cser_interface_desc,
	(struct usb_descriptor_header *) &cser_header_desc,
	(struct usb_descriptor_header *) &cser_call_mgmt_descriptor,
	(struct usb_descriptor_header *) &cser_descriptor,
	(struct usb_descriptor_header *) &cser_union_desc,
	(struct usb_descriptor_header *) &cser_fs_notify_desc,
	(struct usb_descriptor_header *) &cser_fs_in_desc,
	(struct usb_descriptor_header *) &cser_fs_out_desc,
	NULL,
};

/* high speed support: */
static struct usb_endpoint_descriptor cser_hs_notify_desc  = {
	.bLength =		USB_DT_ENDPOINT_SIZE,
	.bDescriptorType =	USB_DT_ENDPOINT,
	.bEndpointAddress =	USB_DIR_IN,
	.bmAttributes =		USB_ENDPOINT_XFER_INT,
	.wMaxPacketSize =	cpu_to_le16(GS_NOTIFY_MAXPACKET),
	.bInterval =		GS_LOG2_NOTIFY_INTERVAL+4,
};

static struct usb_endpoint_descriptor cser_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 cser_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 *cser_hs_function[] = {
	(struct usb_descriptor_header *) &cser_interface_desc,
	(struct usb_descriptor_header *) &cser_header_desc,
	(struct usb_descriptor_header *) &cser_call_mgmt_descriptor,
	(struct usb_descriptor_header *) &cser_descriptor,
	(struct usb_descriptor_header *) &cser_union_desc,
	(struct usb_descriptor_header *) &cser_hs_notify_desc,
	(struct usb_descriptor_header *) &cser_hs_in_desc,
	(struct usb_descriptor_header *) &cser_hs_out_desc,
	NULL,
};

static struct usb_endpoint_descriptor cser_ss_in_desc = {
	.bLength =		USB_DT_ENDPOINT_SIZE,
	.bDescriptorType =	USB_DT_ENDPOINT,
	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
	.wMaxPacketSize =	cpu_to_le16(1024),
};

static struct usb_endpoint_descriptor cser_ss_out_desc = {
	.bLength =		USB_DT_ENDPOINT_SIZE,
	.bDescriptorType =	USB_DT_ENDPOINT,
	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
	.wMaxPacketSize =	cpu_to_le16(1024),
};

static struct usb_ss_ep_comp_descriptor cser_ss_bulk_comp_desc = {
	.bLength =              sizeof(cser_ss_bulk_comp_desc),
	.bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,
};

static struct usb_endpoint_descriptor cser_ss_notify_desc  = {
	.bLength =		USB_DT_ENDPOINT_SIZE,
	.bDescriptorType =	USB_DT_ENDPOINT,
	.bEndpointAddress =	USB_DIR_IN,
	.bmAttributes =		USB_ENDPOINT_XFER_INT,
	.wMaxPacketSize =	cpu_to_le16(GS_NOTIFY_MAXPACKET),
	.bInterval =		GS_LOG2_NOTIFY_INTERVAL+4,
};

static struct usb_ss_ep_comp_descriptor cser_ss_notify_comp_desc = {
	.bLength =		sizeof(cser_ss_notify_comp_desc),
	.bDescriptorType =	USB_DT_SS_ENDPOINT_COMP,

	/* the following 2 values can be tweaked if necessary */
	/* .bMaxBurst =		0, */
	/* .bmAttributes =	0, */
	.wBytesPerInterval =	cpu_to_le16(GS_NOTIFY_MAXPACKET),
};

static struct usb_descriptor_header *cser_ss_function[] = {
	(struct usb_descriptor_header *) &cser_interface_desc,
	(struct usb_descriptor_header *) &cser_header_desc,
	(struct usb_descriptor_header *) &cser_call_mgmt_descriptor,
	(struct usb_descriptor_header *) &cser_descriptor,
	(struct usb_descriptor_header *) &cser_union_desc,
	(struct usb_descriptor_header *) &cser_ss_notify_desc,
	(struct usb_descriptor_header *) &cser_ss_notify_comp_desc,
	(struct usb_descriptor_header *) &cser_ss_in_desc,
	(struct usb_descriptor_header *) &cser_ss_bulk_comp_desc,
	(struct usb_descriptor_header *) &cser_ss_out_desc,
	(struct usb_descriptor_header *) &cser_ss_bulk_comp_desc,
	NULL,
};

/* string descriptors: */
static struct usb_string cser_string_defs[] = {
	[0].s = "CDEV Serial",
	{  } /* end of list */
};

static struct usb_gadget_strings cser_string_table = {
	.language =	0x0409,	/* en-us */
	.strings =	cser_string_defs,
};

static struct usb_gadget_strings *usb_cser_strings[] = {
	&cser_string_table,
	NULL,
};

static inline struct f_cdev *func_to_port(struct usb_function *f)
{
	return container_of(f, struct f_cdev, port_usb.func);
}

static inline struct f_cdev *cser_to_port(struct cserial *cser)
{
	return container_of(cser, struct f_cdev, port_usb);
}

static unsigned int convert_acm_sigs_to_uart(unsigned int acm_sig)
{
	unsigned int uart_sig = 0;

	acm_sig &= (ACM_CTRL_DTR | ACM_CTRL_RTS);
	if (acm_sig & ACM_CTRL_DTR)
		uart_sig |= TIOCM_DTR;

	if (acm_sig & ACM_CTRL_RTS)
		uart_sig |= TIOCM_RTS;

	return uart_sig;
}

static void port_complete_set_line_coding(struct usb_ep *ep,
		struct usb_request *req)
{
	struct f_cdev            *port = ep->driver_data;
	struct usb_composite_dev *cdev = port->port_usb.func.config->cdev;

	if (req->status != 0) {
		dev_dbg(&cdev->gadget->dev, "port(%s) completion, err %d\n",
				port->name, req->status);
		return;
	}

	/* normal completion */
	if (req->actual != sizeof(port->port_usb.port_line_coding)) {
		dev_dbg(&cdev->gadget->dev, "port(%s) short resp, len %d\n",
			port->name, req->actual);
		usb_ep_set_halt(ep);
	} else {
		struct usb_cdc_line_coding	*value = req->buf;

		port->port_usb.port_line_coding = *value;
	}
}

static void usb_cser_free_func(struct usb_function *f)
{
	/* Do nothing as cser_alloc() doesn't alloc anything. */
}

static int
usb_cser_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
{
	struct f_cdev            *port = func_to_port(f);
	struct usb_composite_dev *cdev = f->config->cdev;
	struct usb_request	 *req = cdev->req;
	int			 value = -EOPNOTSUPP;
	u16			 w_index = le16_to_cpu(ctrl->wIndex);
	u16			 w_value = le16_to_cpu(ctrl->wValue);
	u16			 w_length = le16_to_cpu(ctrl->wLength);

	switch ((ctrl->bRequestType << 8) | ctrl->bRequest) {

	/* SET_LINE_CODING ... just read and save what the host sends */
	case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
			| USB_CDC_REQ_SET_LINE_CODING:
		if (w_length != sizeof(struct usb_cdc_line_coding))
			goto invalid;

		value = w_length;
		cdev->gadget->ep0->driver_data = port;
		req->complete = port_complete_set_line_coding;
		break;

	/* GET_LINE_CODING ... return what host sent, or initial value */
	case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
			| USB_CDC_REQ_GET_LINE_CODING:
		value = min_t(unsigned int, w_length,
				sizeof(struct usb_cdc_line_coding));
		memcpy(req->buf, &port->port_usb.port_line_coding, value);
		break;

	case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
			| USB_CDC_REQ_SET_CONTROL_LINE_STATE:

		value = 0;
		port->port_usb.port_handshake_bits = w_value;
		pr_debug("USB_CDC_REQ_SET_CONTROL_LINE_STATE: DTR:%d RST:%d\n",
			w_value & ACM_CTRL_DTR ? 1 : 0,
			w_value & ACM_CTRL_RTS ? 1 : 0);
		if (port->port_usb.notify_modem)
			port->port_usb.notify_modem(port, w_value);

		break;

	default:
invalid:
		dev_dbg(&cdev->gadget->dev,
			"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) {
		dev_dbg(&cdev->gadget->dev,
			"port(%s) req%02x.%02x v%04x i%04x l%d\n",
			port->name, ctrl->bRequestType, ctrl->bRequest,
			w_value, w_index, w_length);
		req->zero = 0;
		req->length = value;
		value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
		if (value < 0)
			pr_err("port response on (%s), err %d\n",
					port->name, value);
	}

	/* device either stalls (value < 0) or reports success */
	return value;
}

static int usb_cser_set_alt(struct usb_function *f, unsigned int intf,
						unsigned int alt)
{
	struct f_cdev *port = func_to_port(f);
	struct usb_composite_dev *cdev	= f->config->cdev;
	int rc = 0;

	if (port->port_usb.notify->driver_data) {
		dev_dbg(&cdev->gadget->dev,
			"reset port(%s)\n", port->name);
		usb_ep_disable(port->port_usb.notify);
	}

	if (!port->port_usb.notify->desc) {
		if (config_ep_by_speed(cdev->gadget, f,
				port->port_usb.notify)) {
			port->port_usb.notify->desc = NULL;
			return -EINVAL;
		}
	}

	rc = usb_ep_enable(port->port_usb.notify);
	if (rc) {
		dev_err(&cdev->gadget->dev, "can't enable %s, result %d\n",
				port->port_usb.notify->name, rc);
		return rc;
	}
	port->port_usb.notify->driver_data = port;

	if (port->port_usb.in->driver_data) {
		dev_dbg(&cdev->gadget->dev,
			"reset port(%s)\n", port->name);
		usb_cser_disconnect(port);
	}
	if (!port->port_usb.in->desc || !port->port_usb.out->desc) {
		dev_dbg(&cdev->gadget->dev,
			"activate port(%s)\n", port->name);
		if (config_ep_by_speed(cdev->gadget, f, port->port_usb.in) ||
			config_ep_by_speed(cdev->gadget, f,
					port->port_usb.out)) {
			port->port_usb.in->desc = NULL;
			port->port_usb.out->desc = NULL;
			return -EINVAL;
		}
	}

	usb_cser_connect(port);
	return rc;
}

static int usb_cser_func_suspend(struct usb_function *f, u8 options)
{
	struct f_cdev	*port = func_to_port(f);

	port->func_wakeup_allowed =
		!!(options & (USB_INTRF_FUNC_SUSPEND_RW >> 8));
	port->func_is_suspended = options & (USB_INTRF_FUNC_SUSPEND_LP >> 8);

	return 0;
}

static int usb_cser_get_status(struct usb_function *f)
{
#ifdef CONFIG_USB_FUNC_WAKEUP_SUPPORTED
	struct f_cdev	*port = func_to_port(f);

	return (port->func_wakeup_allowed ? USB_INTRF_STAT_FUNC_RW : 0) |
		USB_INTRF_STAT_FUNC_RW_CAP;
#else
	return 0;
#endif
}

static void usb_cser_disable(struct usb_function *f)
{
	struct f_cdev	*port = func_to_port(f);
	struct usb_composite_dev *cdev = f->config->cdev;

	dev_dbg(&cdev->gadget->dev,
		"port(%s) deactivated\n", port->name);

	usb_cser_disconnect(port);
	usb_ep_disable(port->port_usb.notify);
	port->port_usb.notify->driver_data = NULL;
}

static int usb_cser_notify(struct f_cdev *port, u8 type, u16 value,
		void *data, unsigned int length)
{
	struct usb_ep			*ep = port->port_usb.notify;
	struct usb_request		*req;
	struct usb_cdc_notification	*notify;
	const unsigned int		len = sizeof(*notify) + length;
	void				*buf;
	int				status;
	unsigned long			flags;

	spin_lock_irqsave(&port->port_lock, flags);
	if (!port->is_connected) {
		spin_unlock_irqrestore(&port->port_lock, flags);
		pr_debug("%s: port disconnected\n", __func__);
		return -ENODEV;
	}

	req = port->port_usb.notify_req;

	req->length = len;
	notify = req->buf;
	buf = notify + 1;

	notify->bmRequestType = USB_DIR_IN | USB_TYPE_CLASS
			| USB_RECIP_INTERFACE;
	notify->bNotificationType = type;
	notify->wValue = cpu_to_le16(value);
	notify->wIndex = cpu_to_le16(port->port_usb.data_id);
	notify->wLength = cpu_to_le16(length);
	/* 2 byte data copy */
	memcpy(buf, data, length);
	spin_unlock_irqrestore(&port->port_lock, flags);

	status = usb_ep_queue(ep, req, GFP_ATOMIC);
	if (status < 0) {
		pr_err("port %s can't notify serial state, %d\n",
				port->name, status);
		spin_lock_irqsave(&port->port_lock, flags);
		port->port_usb.pending = false;
		spin_unlock_irqrestore(&port->port_lock, flags);
	}

	return status;
}

static int port_notify_serial_state(struct cserial *cser)
{
	struct f_cdev *port = cser_to_port(cser);
	int status;
	unsigned long flags;
	struct usb_composite_dev *cdev = port->port_usb.func.config->cdev;

	spin_lock_irqsave(&port->port_lock, flags);
	if (!port->port_usb.pending) {
		port->port_usb.pending = true;
		spin_unlock_irqrestore(&port->port_lock, flags);
		dev_dbg(&cdev->gadget->dev, "port %d serial state %04x\n",
				port->port_num, port->port_usb.serial_state);
		status = usb_cser_notify(port, USB_CDC_NOTIFY_SERIAL_STATE,
				0, &port->port_usb.serial_state,
				sizeof(port->port_usb.serial_state));
		spin_lock_irqsave(&port->port_lock, flags);
	} else {
		port->port_usb.q_again = true;
		status = 0;
	}
	spin_unlock_irqrestore(&port->port_lock, flags);

	return status;
}

static void usb_cser_notify_complete(struct usb_ep *ep, struct usb_request *req)
{
	struct f_cdev *port = req->context;
	unsigned long flags;

	spin_lock_irqsave(&port->port_lock, flags);
	port->port_usb.pending = false;
	if (req->status != -ESHUTDOWN && port->port_usb.q_again) {
		port->port_usb.q_again = false;
		spin_unlock_irqrestore(&port->port_lock, flags);
		port_notify_serial_state(&port->port_usb);
		spin_lock_irqsave(&port->port_lock, flags);
	}
	spin_unlock_irqrestore(&port->port_lock, flags);
}
static void dun_cser_connect(struct cserial *cser)
{
	cser->serial_state |= ACM_CTRL_DSR | ACM_CTRL_DCD;
	port_notify_serial_state(cser);
}

unsigned int dun_cser_get_dtr(struct cserial *cser)
{
	if (cser->port_handshake_bits & ACM_CTRL_DTR)
		return 1;
	else
		return 0;
}

unsigned int dun_cser_get_rts(struct cserial *cser)
{
	if (cser->port_handshake_bits & ACM_CTRL_RTS)
		return 1;
	else
		return 0;
}

unsigned int dun_cser_send_carrier_detect(struct cserial *cser,
				unsigned int yes)
{
	u16 state;

	state = cser->serial_state;
	state &= ~ACM_CTRL_DCD;
	if (yes)
		state |= ACM_CTRL_DCD;

	cser->serial_state = state;
	return port_notify_serial_state(cser);
}

unsigned int dun_cser_send_ring_indicator(struct cserial *cser,
				unsigned int yes)
{
	u16 state;

	state = cser->serial_state;
	state &= ~ACM_CTRL_RI;
	if (yes)
		state |= ACM_CTRL_RI;

	cser->serial_state = state;
	return port_notify_serial_state(cser);
}

static void dun_cser_disconnect(struct cserial *cser)
{
	cser->serial_state &= ~(ACM_CTRL_DSR | ACM_CTRL_DCD);
	port_notify_serial_state(cser);
}

static int dun_cser_send_break(struct cserial *cser, int duration)
{
	u16 state;

	state = cser->serial_state;
	state &= ~ACM_CTRL_BRK;
	if (duration)
		state |= ACM_CTRL_BRK;

	cser->serial_state = state;
	return port_notify_serial_state(cser);
}

static int dun_cser_send_ctrl_bits(struct cserial *cser, int ctrl_bits)
{
	cser->serial_state = ctrl_bits;
	return port_notify_serial_state(cser);
}

static void usb_cser_free_req(struct usb_ep *ep, struct usb_request *req)
{
	if (req) {
		kfree(req->buf);
		usb_ep_free_request(ep, req);
		req = NULL;
	}
}

static void usb_cser_free_requests(struct usb_ep *ep, struct list_head *head)
{
	struct usb_request	*req;

	while (!list_empty(head)) {
		req = list_entry(head->next, struct usb_request, list);
		list_del_init(&req->list);
		usb_cser_free_req(ep, req);
	}
}

static struct usb_request *
usb_cser_alloc_req(struct usb_ep *ep, unsigned int len, gfp_t flags)
{
	struct usb_request *req;

	req = usb_ep_alloc_request(ep, flags);
	if (!req) {
		pr_err("usb alloc request failed\n");
		return 0;
	}

	req->length = len;
	req->buf = kmalloc(len, flags);
	if (!req->buf) {
		pr_err("request buf allocation failed\n");
		usb_ep_free_request(ep, req);
		return 0;
	}

	return req;
}

static int usb_cser_bind(struct usb_configuration *c, struct usb_function *f)
{
	struct usb_composite_dev *cdev = c->cdev;
	struct f_cdev *port = func_to_port(f);
	int status;
	struct usb_ep *ep;
	struct f_cdev_opts *opts =
			container_of(f->fi, struct f_cdev_opts, func_inst);

	if (cser_string_defs[0].id == 0) {
		status = usb_string_id(c->cdev);
		if (status < 0)
			return status;
		cser_string_defs[0].id = status;
		cser_interface_desc.iInterface = status;
	}

	status = usb_interface_id(c, f);
	if (status < 0)
		goto fail;
	port->port_usb.data_id = status;
	cser_interface_desc.bInterfaceNumber = status;
	cser_interface_desc.bInterfaceProtocol = opts->proto;

	status = -ENODEV;
	ep = usb_ep_autoconfig(cdev->gadget, &cser_fs_in_desc);
	if (!ep)
		goto fail;
	port->port_usb.in = ep;
	ep->driver_data = cdev;

	ep = usb_ep_autoconfig(cdev->gadget, &cser_fs_out_desc);
	if (!ep)
		goto fail;
	port->port_usb.out = ep;
	ep->driver_data = cdev;

	ep = usb_ep_autoconfig(cdev->gadget, &cser_fs_notify_desc);
	if (!ep)
		goto fail;
	port->port_usb.notify = ep;
	ep->driver_data = cdev;
	/* allocate notification */
	port->port_usb.notify_req = usb_cser_alloc_req(ep,
			sizeof(struct usb_cdc_notification) + 2, GFP_KERNEL);
	if (!port->port_usb.notify_req)
		goto fail;

	port->port_usb.notify_req->complete = usb_cser_notify_complete;
	port->port_usb.notify_req->context = port;

	cser_hs_in_desc.bEndpointAddress = cser_fs_in_desc.bEndpointAddress;
	cser_hs_out_desc.bEndpointAddress = cser_fs_out_desc.bEndpointAddress;

	cser_ss_in_desc.bEndpointAddress = cser_fs_in_desc.bEndpointAddress;
	cser_ss_out_desc.bEndpointAddress = cser_fs_out_desc.bEndpointAddress;

	if (gadget_is_dualspeed(c->cdev->gadget)) {
		cser_hs_notify_desc.bEndpointAddress =
				cser_fs_notify_desc.bEndpointAddress;
	}
	if (gadget_is_superspeed(c->cdev->gadget)) {
		cser_ss_notify_desc.bEndpointAddress =
				cser_fs_notify_desc.bEndpointAddress;
	}

	status = usb_assign_descriptors(f, cser_fs_function, cser_hs_function,
			cser_ss_function, cser_ss_function);
	if (status)
		goto fail;

	dev_dbg(&cdev->gadget->dev, "usb serial port(%d): %s speed IN/%s OUT/%s\n",
		port->port_num,
		gadget_is_superspeed(c->cdev->gadget) ? "super" :
		gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
		port->port_usb.in->name, port->port_usb.out->name);
	return 0;

fail:
	if (port->port_usb.notify_req)
		usb_cser_free_req(port->port_usb.notify,
				port->port_usb.notify_req);

	if (port->port_usb.notify)
		port->port_usb.notify->driver_data = NULL;
	if (port->port_usb.out)
		port->port_usb.out->driver_data = NULL;
	if (port->port_usb.in)
		port->port_usb.in->driver_data = NULL;

	pr_err("%s: can't bind, err %d\n", f->name, status);
	return status;
}

static void cser_free_inst(struct usb_function_instance *fi)
{
	struct f_cdev_opts *opts;

	opts = container_of(fi, struct f_cdev_opts, func_inst);

	if (opts->port) {
		cdev_device_del(&opts->port->fcdev_cdev, &opts->port->dev);
		mutex_lock(&chardev_ida_lock);
		ida_simple_remove(&chardev_ida, opts->port->minor);
		mutex_unlock(&chardev_ida_lock);
		usb_cser_debugfs_exit(opts->port);
		put_device(&opts->port->dev);
	}

	usb_cser_chardev_deinit();
	kfree(opts->func_name);
	kfree(opts);
}

static void usb_cser_unbind(struct usb_configuration *c, struct usb_function *f)
{
	struct f_cdev *port = func_to_port(f);

	if (port->is_connected)
		usb_cser_disable(f);

	/* Reset string id */
	cser_string_defs[0].id = 0;

	usb_free_all_descriptors(f);
	usb_cser_free_req(port->port_usb.notify, port->port_usb.notify_req);
}

static int usb_cser_alloc_requests(struct usb_ep *ep, struct list_head *head,
		int num, int size,
		void (*cb)(struct usb_ep *ep, struct usb_request *))
{
	int i;
	struct usb_request *req;

	pr_debug("ep:%pK head:%p num:%d size:%d cb:%p\n",
				ep, head, num, size, cb);

	for (i = 0; i < num; i++) {
		req = usb_cser_alloc_req(ep, size, GFP_ATOMIC);
		if (!req) {
			pr_debug("req allocated:%d\n", i);
			return list_empty(head) ? -ENOMEM : 0;
		}
		req->complete = cb;
		list_add_tail(&req->list, head);
	}

	return 0;
}

static void usb_cser_start_rx(struct f_cdev *port)
{
	struct list_head	*pool;
	struct usb_ep		*ep;
	unsigned long		flags;
	int ret;

	pr_debug("start RX(USB OUT)\n");
	if (!port) {
		pr_err("port is null\n");
		return;
	}

	spin_lock_irqsave(&port->port_lock, flags);
	if (!(port->is_connected && port->port_open)) {
		spin_unlock_irqrestore(&port->port_lock, flags);
		pr_debug("can't start rx.\n");
		return;
	}

	pool = &port->read_pool;
	ep = port->port_usb.out;

	while (!list_empty(pool)) {
		struct usb_request	*req;

		req = list_entry(pool->next, struct usb_request, list);
		list_del_init(&req->list);
		req->length = BRIDGE_RX_BUF_SIZE;
		req->complete = usb_cser_read_complete;
		spin_unlock_irqrestore(&port->port_lock, flags);
		ret = usb_ep_queue(ep, req, GFP_KERNEL);
		spin_lock_irqsave(&port->port_lock, flags);
		if (ret) {
			pr_err("port(%d):%pK usb ep(%s) queue failed\n",
					port->port_num, port, ep->name);
			list_add(&req->list, pool);
			break;
		}
	}

	spin_unlock_irqrestore(&port->port_lock, flags);
}

static void usb_cser_read_complete(struct usb_ep *ep, struct usb_request *req)
{
	struct f_cdev *port = ep->driver_data;
	unsigned long flags;
	int ret;

	pr_debug("ep:(%pK)(%s) port:%p req_status:%d req->actual:%u\n",
			ep, ep->name, port, req->status, req->actual);
	if (!port) {
		pr_err("port is null\n");
		return;
	}

	spin_lock_irqsave(&port->port_lock, flags);
	if (!port->port_open) {
		list_add_tail(&req->list, &port->read_pool);
		spin_unlock_irqrestore(&port->port_lock, flags);
		return;
	}

	if (req->status || !req->actual) {
		/*
		 * EPIPE can be returned when host issues clear
		 * EP halt, restart OUT requests if so.
		 */
		if (req->status == -EPIPE) {
			spin_unlock_irqrestore(&port->port_lock, flags);
			ret = usb_ep_queue(ep, req, GFP_KERNEL);
			if (!ret)
				return;
			spin_lock_irqsave(&port->port_lock, flags);
		}
		/*
		 * ECONNRESET is returned when the requests are dequeued
		 * (one reason being send_gadget_ep_cmd failure), add the
		 * requests back to read_pool so that it can requeued.
		 */
		list_add_tail(&req->list, &port->read_pool);
		spin_unlock_irqrestore(&port->port_lock, flags);
		return;
	}

	port->nbytes_from_host += req->actual;
	list_add_tail(&req->list, &port->read_queued);
	spin_unlock_irqrestore(&port->port_lock, flags);

	wake_up(&port->read_wq);
}

static void usb_cser_write_complete(struct usb_ep *ep, struct usb_request *req)
{
	unsigned long flags;
	struct f_cdev *port = ep->driver_data;

	pr_debug("ep:(%pK)(%s) port:%p req_stats:%d\n",
			ep, ep->name, port, req->status);

	if (!port) {
		pr_err("port is null\n");
		return;
	}

	spin_lock_irqsave(&port->port_lock, flags);
	port->nbytes_to_host += req->actual;
	list_add_tail(&req->list, &port->write_pool);
	spin_unlock_irqrestore(&port->port_lock, flags);

	switch (req->status) {
	default:
		pr_debug("unexpected %s status %d\n", ep->name, req->status);
		fallthrough;
	case 0:
		/* normal completion */
		break;

	case -ESHUTDOWN:
		/* disconnect */
		pr_debug("%s shutdown\n", ep->name);
		break;
	}
}

static void usb_cser_start_io(struct f_cdev *port)
{
	int ret = -ENODEV;
	unsigned long	flags;

	pr_debug("port: %pK\n", port);

	spin_lock_irqsave(&port->port_lock, flags);
	if (!port->is_connected)
		goto start_io_out;

	port->current_rx_req = NULL;
	port->pending_rx_bytes = 0;
	port->current_rx_buf = NULL;

	ret = usb_cser_alloc_requests(port->port_usb.out,
				&port->read_pool,
				BRIDGE_RX_QUEUE_SIZE, BRIDGE_RX_BUF_SIZE,
				usb_cser_read_complete);
	if (ret) {
		pr_err("unable to allocate out requests\n");
		goto start_io_out;
	}

	ret = usb_cser_alloc_requests(port->port_usb.in,
				&port->write_pool,
				BRIDGE_TX_QUEUE_SIZE, BRIDGE_TX_BUF_SIZE,
				usb_cser_write_complete);
	if (ret) {
		usb_cser_free_requests(port->port_usb.out, &port->read_pool);
		pr_err("unable to allocate IN requests\n");
		goto start_io_out;
	}

start_io_out:
	spin_unlock_irqrestore(&port->port_lock, flags);
	if (ret)
		return;

	usb_cser_start_rx(port);
}

static void usb_cser_stop_io(struct f_cdev *port)
{
	struct usb_ep	*in;
	struct usb_ep	*out;
	unsigned long	flags;

	pr_debug("port:%pK\n", port);

	in = port->port_usb.in;
	out = port->port_usb.out;

	/* disable endpoints, aborting down any active I/O */
	usb_ep_disable(out);
	out->driver_data = NULL;
	usb_ep_disable(in);
	in->driver_data = NULL;

	spin_lock_irqsave(&port->port_lock, flags);
	if (port->current_rx_req != NULL) {
		kfree(port->current_rx_req->buf);
		usb_ep_free_request(out, port->current_rx_req);
	}

	port->pending_rx_bytes = 0;
	port->current_rx_buf = NULL;
	usb_cser_free_requests(out, &port->read_queued);
	usb_cser_free_requests(out, &port->read_pool);
	usb_cser_free_requests(in, &port->write_pool);
	spin_unlock_irqrestore(&port->port_lock, flags);
}

int f_cdev_open(struct inode *inode, struct file *file)
{
	int ret;
	unsigned long flags;
	struct f_cdev *port;

	port = container_of(inode->i_cdev, struct f_cdev, fcdev_cdev);
	get_device(&port->dev);
	if (port->port_open) {
		pr_err("port is already opened.\n");
		put_device(&port->dev);
		return -EBUSY;
	}

	file->private_data = port;
	pr_debug("opening port(%s)(%pK)\n", port->name, port);
	ret = wait_event_interruptible(port->open_wq,
					port->is_connected);
	if (ret) {
		pr_debug("open interrupted.\n");
		put_device(&port->dev);
		return ret;
	}

	spin_lock_irqsave(&port->port_lock, flags);
	port->port_open = true;
	spin_unlock_irqrestore(&port->port_lock, flags);
	usb_cser_start_rx(port);

	pr_debug("port(%s)(%pK) open is success\n", port->name, port);

	return 0;
}

int f_cdev_release(struct inode *inode, struct file *file)
{
	unsigned long flags;
	struct f_cdev *port;

	port = file->private_data;
	spin_lock_irqsave(&port->port_lock, flags);
	port->port_open = false;
	port->cbits_updated = false;
	spin_unlock_irqrestore(&port->port_lock, flags);
	pr_debug("port(%s)(%pK) is closed.\n", port->name, port);
	put_device(&port->dev);

	return 0;
}

ssize_t f_cdev_read(struct file *file,
		       char __user *buf,
		       size_t count,
		       loff_t *ppos)
{
	unsigned long flags;
	struct f_cdev *port;
	struct usb_request *req;
	struct list_head *pool;
	struct usb_request *current_rx_req;
	size_t pending_rx_bytes, bytes_copied = 0, size;
	u8 *current_rx_buf;

	port = file->private_data;
	if (!port) {
		pr_err("port is NULL.\n");
		return -EINVAL;
	}

	pr_debug("read on port(%s)(%pK) count:%zu\n", port->name, port, count);
	spin_lock_irqsave(&port->port_lock, flags);
	current_rx_req = port->current_rx_req;
	pending_rx_bytes = port->pending_rx_bytes;
	current_rx_buf = port->current_rx_buf;
	port->current_rx_req = NULL;
	port->current_rx_buf = NULL;
	port->pending_rx_bytes = 0;
	bytes_copied = 0;

	if (list_empty(&port->read_queued) && !pending_rx_bytes) {
		spin_unlock_irqrestore(&port->port_lock, flags);
		pr_debug("%s(): read_queued list is empty.\n", __func__);
		goto start_rx;
	}

	/*
	 * Consider below cases:
	 * 1. If available read buffer size (i.e. count value) is greater than
	 * available data as part of one USB OUT request buffer, then consider
	 * copying multiple USB OUT request buffers until read buffer is filled.
	 * 2. If available read buffer size (i.e. count value) is smaller than
	 * available data as part of one USB OUT request buffer, then copy this
	 * buffer data across multiple read() call until whole USB OUT request
	 * buffer is copied.
	 */
	while ((pending_rx_bytes || !list_empty(&port->read_queued)) && count) {
		if (pending_rx_bytes == 0) {
			pool = &port->read_queued;
			req = list_first_entry(pool, struct usb_request, list);
			list_del_init(&req->list);
			current_rx_req = req;
			pending_rx_bytes = req->actual;
			current_rx_buf = req->buf;
		}

		spin_unlock_irqrestore(&port->port_lock, flags);
		size = count;
		if (size > pending_rx_bytes)
			size = pending_rx_bytes;

		pr_debug("pending_rx_bytes:%zu count:%zu size:%zu\n",
					pending_rx_bytes, count, size);
		size -= copy_to_user(buf, current_rx_buf, size);
		port->nbytes_to_port_bridge += size;
		bytes_copied += size;
		count -= size;
		buf += size;

		spin_lock_irqsave(&port->port_lock, flags);
		if (!port->is_connected) {
			list_add_tail(&current_rx_req->list, &port->read_pool);
			spin_unlock_irqrestore(&port->port_lock, flags);
			return -EAGAIN;
		}

		/*
		 * partial data available, then update pending_rx_bytes,
		 * otherwise add USB request back to read_pool for next data.
		 */
		if (size < pending_rx_bytes) {
			pending_rx_bytes -= size;
			current_rx_buf += size;
		} else {
			list_add_tail(&current_rx_req->list, &port->read_pool);
			pending_rx_bytes = 0;
			current_rx_req = NULL;
			current_rx_buf = NULL;
		}
	}

	port->pending_rx_bytes = pending_rx_bytes;
	port->current_rx_buf = current_rx_buf;
	port->current_rx_req = current_rx_req;
	spin_unlock_irqrestore(&port->port_lock, flags);

start_rx:
	usb_cser_start_rx(port);
	return bytes_copied;
}

ssize_t f_cdev_write(struct file *file,
		       const char __user *buf,
		       size_t count,
		       loff_t *ppos)
{
	int ret;
	unsigned long flags;
	struct f_cdev *port;
	struct usb_request *req;
	struct list_head *pool;
	unsigned int xfer_size;
	struct usb_ep *in;

	port = file->private_data;
	if (!port) {
		pr_err("port is NULL.\n");
		return -EINVAL;
	}

	spin_lock_irqsave(&port->port_lock, flags);
	pr_debug("write on port(%s)(%pK)\n", port->name, port);

	if (!port->is_connected) {
		spin_unlock_irqrestore(&port->port_lock, flags);
		pr_err("%s: cable is disconnected.\n", __func__);
		return -ENODEV;
	}

	if (list_empty(&port->write_pool)) {
		spin_unlock_irqrestore(&port->port_lock, flags);
		pr_debug("%s: Request list is empty.\n", __func__);
		return 0;
	}

	in = port->port_usb.in;
	pool = &port->write_pool;
	req = list_first_entry(pool, struct usb_request, list);
	list_del_init(&req->list);
	spin_unlock_irqrestore(&port->port_lock, flags);

	pr_debug("%s: write buf size:%zu\n", __func__, count);
	if (count > BRIDGE_TX_BUF_SIZE)
		xfer_size = BRIDGE_TX_BUF_SIZE;
	else
		xfer_size = count;

	ret = copy_from_user(req->buf, buf, xfer_size);
	if (ret) {
		pr_err("copy_from_user failed: err %d\n", ret);
		ret = -EFAULT;
	} else {
		req->length = xfer_size;
		req->zero = 1;
		ret = usb_ep_queue(in, req, GFP_KERNEL);
		if (ret) {
			pr_err("EP QUEUE failed:%d\n", ret);
			ret = -EIO;
			goto err_exit;
		}
		spin_lock_irqsave(&port->port_lock, flags);
		port->nbytes_from_port_bridge += req->length;
		spin_unlock_irqrestore(&port->port_lock, flags);
	}

err_exit:
	if (ret) {
		spin_lock_irqsave(&port->port_lock, flags);
		/* USB cable is connected, add it back otherwise free request */
		if (port->is_connected)
			list_add(&req->list, &port->write_pool);
		else
			usb_cser_free_req(in, req);
		spin_unlock_irqrestore(&port->port_lock, flags);
		return ret;
	}

	return xfer_size;
}

static unsigned int f_cdev_poll(struct file *file, poll_table *wait)
{
	unsigned int mask = 0;
	struct f_cdev *port;
	unsigned long flags;

	port = file->private_data;
	if (port && port->is_connected) {
		poll_wait(file, &port->read_wq, wait);
		spin_lock_irqsave(&port->port_lock, flags);
		if (!list_empty(&port->read_queued)) {
			mask |= POLLIN | POLLRDNORM;
			pr_debug("sets POLLIN for %s\n", port->name);
		}

		if (port->cbits_updated) {
			mask |= POLLPRI;
			pr_debug("sets POLLPRI for %s\n", port->name);
		}
		spin_unlock_irqrestore(&port->port_lock, flags);
	} else {
		pr_err("Failed due to NULL device or disconnected.\n");
		mask = POLLERR;
	}

	return mask;
}

static int f_cdev_tiocmget(struct f_cdev *port)
{
	struct cserial	*cser;
	unsigned int result = 0;

	if (!port) {
		pr_err("port is NULL.\n");
		return -ENODEV;
	}

	cser = &port->port_usb;
	if (cser->get_dtr)
		result |= (cser->get_dtr(cser) ? TIOCM_DTR : 0);

	if (cser->get_rts)
		result |= (cser->get_rts(cser) ? TIOCM_RTS : 0);

	if (cser->serial_state & TIOCM_CD)
		result |= TIOCM_CD;

	if (cser->serial_state & TIOCM_RI)
		result |= TIOCM_RI;
	return result;
}

static int f_cdev_tiocmset(struct f_cdev *port,
			unsigned int set, unsigned int clear)
{
	struct cserial *cser;
	int status = 0;

	if (!port) {
		pr_err("port is NULL.\n");
		return -ENODEV;
	}

	cser = &port->port_usb;
	if (set & TIOCM_RI) {
		if (cser->send_ring_indicator) {
			cser->serial_state |= TIOCM_RI;
			status = cser->send_ring_indicator(cser, 1);
		}
	}
	if (clear & TIOCM_RI) {
		if (cser->send_ring_indicator) {
			cser->serial_state &= ~TIOCM_RI;
			status = cser->send_ring_indicator(cser, 0);
		}
	}
	if (set & TIOCM_CD) {
		if (cser->send_carrier_detect) {
			cser->serial_state |= TIOCM_CD;
			status = cser->send_carrier_detect(cser, 1);
		}
	}
	if (clear & TIOCM_CD) {
		if (cser->send_carrier_detect) {
			cser->serial_state &= ~TIOCM_CD;
			status = cser->send_carrier_detect(cser, 0);
		}
	}

	return status;
}

static long f_cdev_ioctl(struct file *fp, unsigned int cmd,
						unsigned long arg)
{
	long ret = 0;
	int i = 0;
	uint32_t val;
	struct f_cdev *port;

	port = fp->private_data;
	if (!port) {
		pr_err("port is null.\n");
		return POLLERR;
	}

	switch (cmd) {
	case TIOCMBIC:
	case TIOCMBIS:
	case TIOCMSET:
		pr_debug("TIOCMSET on port(%s)%pK\n", port->name, port);
		i = get_user(val, (uint32_t *)arg);
		if (i) {
			pr_err("Error getting TIOCMSET value\n");
			return i;
		}
		ret = f_cdev_tiocmset(port, val, ~val);
		break;
	case TIOCMGET:
		pr_debug("TIOCMGET on port(%s)%pK\n", port->name, port);
		ret = f_cdev_tiocmget(port);
		if (ret >= 0) {
			ret = put_user(ret, (uint32_t *)arg);
			port->cbits_updated = false;
		}
		break;
	default:
		pr_err("Received cmd:%d not supported\n", cmd);
		ret = -ENOIOCTLCMD;
		break;
	}

	return ret;
}

static void usb_cser_notify_modem(void *fport, int ctrl_bits)
{
	int temp;
	struct f_cdev *port = fport;

	if (!port) {
		pr_err("port is null\n");
		return;
	}

	pr_debug("port(%s): ctrl_bits:%x\n", port->name, ctrl_bits);

	temp = convert_acm_sigs_to_uart(ctrl_bits);

	if (temp == port->cbits_to_modem)
		return;

	port->cbits_to_modem = temp;
	port->cbits_updated = true;

	wake_up(&port->read_wq);
}

int usb_cser_connect(struct f_cdev *port)
{
	unsigned long flags;
	int ret;
	struct cserial *cser;

	if (!port) {
		pr_err("port is NULL.\n");
		return -ENODEV;
	}

	pr_debug("port(%s) (%pK)\n", port->name, port);

	cser = &port->port_usb;
	cser->notify_modem = usb_cser_notify_modem;

	ret = usb_ep_enable(cser->in);
	if (ret) {
		pr_err("usb_ep_enable failed eptype:IN ep:%pK, err:%d\n",
					cser->in, ret);
		return ret;
	}
	cser->in->driver_data = port;

	ret = usb_ep_enable(cser->out);
	if (ret) {
		pr_err("usb_ep_enable failed eptype:OUT ep:%pK, err: %d\n",
					cser->out, ret);
		cser->in->driver_data = 0;
		return ret;
	}
	cser->out->driver_data = port;

	spin_lock_irqsave(&port->port_lock, flags);
	cser->pending = false;
	cser->q_again = false;
	port->is_connected = true;
	spin_unlock_irqrestore(&port->port_lock, flags);

	usb_cser_start_io(port);
	wake_up(&port->open_wq);
	return 0;
}

void usb_cser_disconnect(struct f_cdev *port)
{
	unsigned long flags;

	usb_cser_stop_io(port);

	/* lower DTR to modem */
	usb_cser_notify_modem(port, 0);

	spin_lock_irqsave(&port->port_lock, flags);
	port->is_connected = false;
	port->nbytes_from_host = port->nbytes_to_host = 0;
	port->nbytes_to_port_bridge = 0;
	spin_unlock_irqrestore(&port->port_lock, flags);
}

static const struct file_operations f_cdev_fops = {
	.owner = THIS_MODULE,
	.open = f_cdev_open,
	.release = f_cdev_release,
	.read = f_cdev_read,
	.write = f_cdev_write,
	.poll = f_cdev_poll,
	.unlocked_ioctl = f_cdev_ioctl,
	.compat_ioctl = f_cdev_ioctl,
};

static ssize_t cser_rw_write(struct file *file, const char __user *ubuf,
				size_t count, loff_t *ppos)
{
	struct seq_file *s = file->private_data;
	struct f_cdev *port = s->private;
	u8 input;
	struct cserial *cser;
	struct usb_function *func;
	struct usb_gadget *gadget;
	int ret;

	cser = &port->port_usb;
	if (!cser) {
		pr_err("cser is NULL\n");
		return -EINVAL;
	}

	if (!port->is_connected) {
		pr_debug("port disconnected\n");
		return -ENODEV;
	}

	func = &cser->func;
	if (!func) {
		pr_err("func is NULL\n");
		return -EINVAL;
	}

	if (ubuf == NULL) {
		pr_debug("buffer is Null.\n");
		goto err;
	}

	ret = kstrtou8_from_user(ubuf, count, 0, &input);
	if (ret) {
		pr_err("Invalid value. err:%d\n", ret);
		goto err;
	}

	if (port->debugfs_rw_enable == !!input) {
		if (!!input)
			pr_debug("RW already enabled\n");
		else
			pr_debug("RW already disabled\n");
		goto err;
	}

	port->debugfs_rw_enable = !!input;
	if (port->debugfs_rw_enable) {
		gadget = cser->func.config->cdev->gadget;
		if (gadget->speed >= USB_SPEED_SUPER &&
			port->func_is_suspended) {
			ret = -EPERM;
#ifdef CONFIG_USB_FUNC_WAKEUP_SUPPORTED
			pr_debug("Calling usb_func_wakeup\n");
			ret = usb_func_wakeup(func);
#endif
		} else {
			pr_debug("Calling usb_gadget_wakeup\n");
			ret = usb_gadget_wakeup(gadget);
		}

		if ((ret == -EBUSY) || (ret == -EAGAIN))
			pr_debug("RW delayed due to LPM exit.\n");
		else if (ret)
			pr_err("wakeup failed. ret=%d.\n", ret);
	} else {
		pr_debug("RW disabled.\n");
	}
err:
	return count;
}

static int usb_cser_rw_show(struct seq_file *s, void *unused)
{
	struct f_cdev *port = s->private;

	if (!port) {
		pr_err("port is null\n");
		return 0;
	}

	seq_printf(s, "%d\n", port->debugfs_rw_enable);

	return 0;
}

static int debug_cdev_rw_open(struct inode *inode, struct file *f)
{
	return single_open(f, usb_cser_rw_show, inode->i_private);
}

static const struct file_operations cser_rem_wakeup_fops = {
	.open = debug_cdev_rw_open,
	.read = seq_read,
	.write = cser_rw_write,
	.owner = THIS_MODULE,
	.llseek = seq_lseek,
	.release = seq_release,
};

static void usb_cser_debugfs_init(struct f_cdev *port)
{
	port->debugfs_root = debugfs_create_dir(port->name, NULL);
	if (IS_ERR(port->debugfs_root))
		return;

	debugfs_create_file("remote_wakeup", 0600,
			port->debugfs_root, port, &cser_rem_wakeup_fops);
}

static void usb_cser_debugfs_exit(struct f_cdev *port)
{
	debugfs_remove_recursive(port->debugfs_root);
}

static void cdev_device_release(struct device *dev)
{
	struct f_cdev *port = container_of(dev, struct f_cdev, dev);

	pr_debug("Free cdev port(%d)\n", port->port_num);
	kfree(port);
}

static struct f_cdev *f_cdev_alloc(char *func_name, int portno)
{
	int ret;
	struct f_cdev *port;

	port = kzalloc(sizeof(struct f_cdev), GFP_KERNEL);
	if (!port) {
		ret = -ENOMEM;
		return  ERR_PTR(ret);
	}

	mutex_lock(&chardev_ida_lock);
	if (ida_is_empty(&chardev_ida)) {
		ret = usb_cser_alloc_chardev_region();
		if (ret) {
			mutex_unlock(&chardev_ida_lock);
			pr_err("alloc chardev failed\n");
			goto err_alloc_chardev;
		}
	}

	ret = ida_simple_get(&chardev_ida, 0, 0, GFP_KERNEL);
	if (ret >= NUM_INSTANCE) {
		ida_simple_remove(&chardev_ida, ret);
		mutex_unlock(&chardev_ida_lock);
		ret = -ENODEV;
		goto err_get_ida;
	}

	port->port_num = portno;
	port->minor = ret;
	mutex_unlock(&chardev_ida_lock);

	snprintf(port->name, sizeof(port->name), "%s%d", DEVICE_NAME, portno);
	spin_lock_init(&port->port_lock);

	init_waitqueue_head(&port->open_wq);
	init_waitqueue_head(&port->read_wq);
	INIT_LIST_HEAD(&port->read_pool);
	INIT_LIST_HEAD(&port->read_queued);
	INIT_LIST_HEAD(&port->write_pool);

	port->fcdev_wq = create_singlethread_workqueue(port->name);
	if (!port->fcdev_wq) {
		pr_err("Unable to create workqueue fcdev_wq for port:%s\n",
						port->name);
		ret = -ENOMEM;
		goto err_get_ida;
	}

	/* create char device */
	cdev_init(&port->fcdev_cdev, &f_cdev_fops);
	device_initialize(&port->dev);
	port->dev.class = fcdev_classp;
	port->dev.parent = NULL;
	port->dev.release = cdev_device_release;
	port->dev.devt = MKDEV(major, port->minor);
	dev_set_name(&port->dev, port->name);
	ret = cdev_device_add(&port->fcdev_cdev, &port->dev);
	if (ret) {
		pr_err("Failed to add cdev for port(%s)\n", port->name);
		goto err_cdev_add;
	}

	usb_cser_debugfs_init(port);

	pr_info("port_name:%s (%pK) portno:(%d)\n",
			port->name, port, port->port_num);
	return port;

err_cdev_add:
	destroy_workqueue(port->fcdev_wq);
err_get_ida:
	usb_cser_chardev_deinit();
err_alloc_chardev:
	kfree(port);

	return ERR_PTR(ret);
}

static void usb_cser_chardev_deinit(void)
{

	if (ida_is_empty(&chardev_ida)) {

		if (major) {
			unregister_chrdev_region(MKDEV(major, 0), minors);
			major = minors = 0;
		}

		if (!IS_ERR_OR_NULL(fcdev_classp))
			class_destroy(fcdev_classp);
	}
}

static int usb_cser_alloc_chardev_region(void)
{
	int ret;
	dev_t dev;

	ret = alloc_chrdev_region(&dev,
			       0,
			       NUM_INSTANCE,
			       MODULE_NAME);
	if (ret) {
		pr_err("alloc_chrdev_region() failed ret:%i\n", ret);
		return ret;
	}

	major = MAJOR(dev);
	minors = NUM_INSTANCE;

	fcdev_classp = class_create(THIS_MODULE, MODULE_NAME);
	if (IS_ERR(fcdev_classp)) {
		pr_err("class_create() failed ENOMEM\n");
		ret = -ENOMEM;
	}

	return 0;
}

static inline struct f_cdev_opts *to_f_cdev_opts(struct config_item *item)
{
	return container_of(to_config_group(item), struct f_cdev_opts,
			func_inst.group);
}

static struct f_cdev_opts *to_fi_cdev_opts(struct usb_function_instance *fi)
{
	return container_of(fi, struct f_cdev_opts, func_inst);
}

static void cserial_attr_release(struct config_item *item)
{
	struct f_cdev_opts *opts = to_f_cdev_opts(item);

	usb_put_function_instance(&opts->func_inst);
}

static struct configfs_item_operations cserial_item_ops = {
	.release	= cserial_attr_release,
};

static ssize_t usb_cser_status_show(struct config_item *item, char *page)
{
	struct f_cdev *port = to_f_cdev_opts(item)->port;
	char *buf;
	unsigned long flags;
	int temp = 0;
	int ret;

	buf = kzalloc(sizeof(char) * 512, GFP_KERNEL);
	if (!buf)
		return -ENOMEM;

	spin_lock_irqsave(&port->port_lock, flags);
	temp += scnprintf(buf + temp, 512 - temp,
			"###PORT:%s###\n"
			"port_no:%d\n"
			"func:%s\n"
			"nbytes_to_host: %lu\n"
			"nbytes_from_host: %lu\n"
			"nbytes_to_port_bridge:  %lu\n"
			"nbytes_from_port_bridge: %lu\n"
			"cbits_to_modem:  %u\n"
			"Port Opened: %s\n",
			port->name,
			port->port_num,
			to_f_cdev_opts(item)->func_name,
			port->nbytes_to_host,
			port->nbytes_from_host,
			port->nbytes_to_port_bridge,
			port->nbytes_from_port_bridge,
			port->cbits_to_modem,
			(port->port_open ? "Opened" : "Closed"));
	spin_unlock_irqrestore(&port->port_lock, flags);

	ret = scnprintf(page, temp, buf);
	kfree(buf);

	return ret;
}

static ssize_t usb_cser_status_store(struct config_item *item,
			const char *page, size_t len)
{
	struct f_cdev *port = to_f_cdev_opts(item)->port;
	unsigned long flags;
	u8 stats;

	if (page == NULL) {
		pr_err("Invalid buffer\n");
		return len;
	}

	if (kstrtou8(page, 0, &stats) != 0 || stats != 0) {
		pr_err("(%u)Wrong value. enter 0 to clear.\n", stats);
		return len;
	}

	spin_lock_irqsave(&port->port_lock, flags);
	port->nbytes_to_host = port->nbytes_from_host = 0;
	port->nbytes_to_port_bridge = port->nbytes_from_port_bridge = 0;
	spin_unlock_irqrestore(&port->port_lock, flags);

	return len;
}

CONFIGFS_ATTR(usb_cser_, status);
static struct configfs_attribute *cserial_attrs[] = {
	&usb_cser_attr_status,
	NULL,
};

static struct config_item_type cserial_func_type = {
	.ct_item_ops	= &cserial_item_ops,
	.ct_attrs	= cserial_attrs,
	.ct_owner	= THIS_MODULE,
};

static int cser_set_inst_name(struct usb_function_instance *f, const char *name)
{
	struct f_cdev_opts *opts =
		container_of(f, struct f_cdev_opts, func_inst);
	char *ptr, *str;
	size_t name_len, str_size;
	int ret;
	struct f_cdev *port;

	name_len = strlen(name) + 1;
	if (name_len > MAX_CDEV_INST_NAME)
		return -ENAMETOOLONG;

	/* expect name as cdev.<func>.<port_num> */
	str = strnchr(name, strlen(name), '.');
	if (!str) {
		pr_err("invalid input (%s)\n", name);
		return -EINVAL;
	}

	/* get function name */
	str_size = name_len - strlen(str);
	if (str_size > MAX_CDEV_FUNC_NAME)
		return -ENAMETOOLONG;

	ptr = kstrndup(name, str_size - 1, GFP_KERNEL);
	if (!ptr) {
		pr_err("error:%ld\n", PTR_ERR(ptr));
		return -ENOMEM;
	}

	opts->func_name = ptr;

	/* get port number */
	str = strrchr(name, '.');
	if (!str) {
		pr_err("err: port number not found\n");
		return -EINVAL;
	}
	pr_debug("str:%s\n", str);

	*str = '\0';
	str++;

	ret = kstrtou8(str, 0, &opts->port_num);
	if (ret) {
		pr_err("erro: not able to get port number\n");
		return -EINVAL;
	}

	pr_debug("gser: port_num:%d func_name:%s\n",
			opts->port_num, opts->func_name);

	port = f_cdev_alloc(opts->func_name, opts->port_num);
	if (IS_ERR(port)) {
		pr_err("Failed to create cdev port(%d)\n", opts->port_num);
		return -ENOMEM;
	}

	opts->port = port;

	/* For DUN functionality only sets control signal handling */
	if (!strcmp(opts->func_name, "dun")) {
		port->port_usb.connect = dun_cser_connect;
		port->port_usb.get_dtr = dun_cser_get_dtr;
		port->port_usb.get_rts = dun_cser_get_rts;
		port->port_usb.send_carrier_detect =
				dun_cser_send_carrier_detect;
		port->port_usb.send_ring_indicator =
				dun_cser_send_ring_indicator;
		port->port_usb.send_modem_ctrl_bits = dun_cser_send_ctrl_bits;
		port->port_usb.disconnect = dun_cser_disconnect;
		port->port_usb.send_break = dun_cser_send_break;
		opts->proto = 0x40;
	} else {
		opts->proto = 0x60;
	}

	return 0;
}

static struct usb_function_instance *cser_alloc_inst(void)
{
	struct f_cdev_opts *opts;

	opts = kzalloc(sizeof(*opts), GFP_KERNEL);
	if (!opts)
		return ERR_PTR(-ENOMEM);

	opts->func_inst.free_func_inst = cser_free_inst;
	opts->func_inst.set_inst_name = cser_set_inst_name;

	config_group_init_type_name(&opts->func_inst.group, "",
				    &cserial_func_type);
	return &opts->func_inst;
}

static struct usb_function *cser_alloc(struct usb_function_instance *fi)
{
	struct f_cdev_opts *opts = to_fi_cdev_opts(fi);
	struct f_cdev *port = opts->port;

	port->port_usb.func.name = "cser";
	port->port_usb.func.strings = usb_cser_strings;
	port->port_usb.func.bind = usb_cser_bind;
	port->port_usb.func.unbind = usb_cser_unbind;
	port->port_usb.func.set_alt = usb_cser_set_alt;
	port->port_usb.func.disable = usb_cser_disable;
	port->port_usb.func.setup = usb_cser_setup;
	port->port_usb.func.func_suspend = usb_cser_func_suspend;
	port->port_usb.func.get_status = usb_cser_get_status;
	port->port_usb.func.free_func = usb_cser_free_func;

	return &port->port_usb.func;
}

DECLARE_USB_FUNCTION_INIT(cser, cser_alloc_inst, cser_alloc);
MODULE_DESCRIPTION("USB Serial Character Driver");
MODULE_LICENSE("GPL");