text: /*
   * USB Serial Converter Generic functions
   *
   * Copyright (C) 2010 - 2013 Johan Hovold (jhovold@gmail.com)
   * Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@kroah.com)
   *
   *	This program is free software; you can redistribute it and/or
   *	modify it under the terms of the GNU General Public License version
   *	2 as published by the Free Software Foundation.
   */
  
  #include <linux/kernel.h>
  #include <linux/sched/signal.h>
  #include <linux/errno.h>
  #include <linux/slab.h>
  #include <linux/sysrq.h>
  #include <linux/tty.h>
  #include <linux/tty_flip.h>
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/usb.h>
  #include <linux/usb/serial.h>
  #include <linux/uaccess.h>
  #include <linux/kfifo.h>
  #include <linux/serial.h>
  
  #ifdef CONFIG_USB_SERIAL_GENERIC
  
  static __u16 vendor  = 0x05f9;
  static __u16 product = 0xffff;
  
  module_param(vendor, ushort, 0);
  MODULE_PARM_DESC(vendor, "User specified USB idVendor");
  
  module_param(product, ushort, 0);
  MODULE_PARM_DESC(product, "User specified USB idProduct");
  
  static struct usb_device_id generic_device_ids[2]; /* Initially all zeroes. */
  
  static int usb_serial_generic_probe(struct usb_serial *serial,
  					const struct usb_device_id *id)
  {
  	struct device *dev = &serial->interface->dev;
  
  	dev_info(dev, "The \"generic\" usb-serial driver is only for testing and one-off prototypes.\n");
  	dev_info(dev, "Tell linux-usb@vger.kernel.org to add your device to a proper driver.\n");
  
  	return 0;
  }
  
  static int usb_serial_generic_calc_num_ports(struct usb_serial *serial,
  					struct usb_serial_endpoints *epds)
  {
  	struct device *dev = &serial->interface->dev;
  	int num_ports;
  
  	num_ports = max(epds->num_bulk_in, epds->num_bulk_out);
  
  	if (num_ports == 0) {
  		dev_err(dev, "device has no bulk endpoints\n");
  		return -ENODEV;
  	}
  
  	return num_ports;
  }
  
  static struct usb_serial_driver usb_serial_generic_device = {
  	.driver = {
  		.owner =	THIS_MODULE,
  		.name =		"generic",
  	},
  	.id_table =		generic_device_ids,
  	.probe =		usb_serial_generic_probe,
  	.calc_num_ports =	usb_serial_generic_calc_num_ports,
  	.throttle =		usb_serial_generic_throttle,
  	.unthrottle =		usb_serial_generic_unthrottle,
  	.resume =		usb_serial_generic_resume,
  };
  
  static struct usb_serial_driver * const serial_drivers[] = {
  	&usb_serial_generic_device, NULL
  };
  
  #endif
  
  int usb_serial_generic_register(void)
  {
  	int retval = 0;
  
  #ifdef CONFIG_USB_SERIAL_GENERIC
  	generic_device_ids[0].idVendor = vendor;
  	generic_device_ids[0].idProduct = product;
  	generic_device_ids[0].match_flags =
  		USB_DEVICE_ID_MATCH_VENDOR | USB_DEVICE_ID_MATCH_PRODUCT;
  
  	retval = usb_serial_register_drivers(serial_drivers,
  			"usbserial_generic", generic_device_ids);
  #endif
  	return retval;
  }
  
  void usb_serial_generic_deregister(void)
  {
  #ifdef CONFIG_USB_SERIAL_GENERIC
  	usb_serial_deregister_drivers(serial_drivers);
  #endif
  }
  
  int usb_serial_generic_open(struct tty_struct *tty, struct usb_serial_port *port)
  {
  	int result = 0;
  	unsigned long flags;
  
  	spin_lock_irqsave(&port->lock, flags);
  	port->throttled = 0;
  	port->throttle_req = 0;
  	spin_unlock_irqrestore(&port->lock, flags);
  
  	if (port->bulk_in_size)
  		result = usb_serial_generic_submit_read_urbs(port, GFP_KERNEL);
  
  	return result;
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_open);
  
  void usb_serial_generic_close(struct usb_serial_port *port)
  {
  	unsigned long flags;
  	int i;
  
  	if (port->bulk_out_size) {
  		for (i = 0; i < ARRAY_SIZE(port->write_urbs); ++i)
  			usb_kill_urb(port->write_urbs[i]);
  
  		spin_lock_irqsave(&port->lock, flags);
  		kfifo_reset_out(&port->write_fifo);
  		spin_unlock_irqrestore(&port->lock, flags);
  	}
  	if (port->bulk_in_size) {
  		for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i)
  			usb_kill_urb(port->read_urbs[i]);
  	}
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_close);
  
  int usb_serial_generic_prepare_write_buffer(struct usb_serial_port *port,
  						void *dest, size_t size)
  {
  	return kfifo_out_locked(&port->write_fifo, dest, size, &port->lock);
  }
  
  /**
   * usb_serial_generic_write_start - start writing buffered data
   * @port: usb-serial port
   * @mem_flags: flags to use for memory allocations
   *
   * Serialised using USB_SERIAL_WRITE_BUSY flag.
   *
   * Return: Zero on success or if busy, otherwise a negative errno value.
   */
  int usb_serial_generic_write_start(struct usb_serial_port *port,
  							gfp_t mem_flags)
  {
  	struct urb *urb;
  	int count, result;
  	unsigned long flags;
  	int i;
  
  	if (test_and_set_bit_lock(USB_SERIAL_WRITE_BUSY, &port->flags))
  		return 0;
  retry:
  	spin_lock_irqsave(&port->lock, flags);
  	if (!port->write_urbs_free || !kfifo_len(&port->write_fifo)) {
  		clear_bit_unlock(USB_SERIAL_WRITE_BUSY, &port->flags);
  		spin_unlock_irqrestore(&port->lock, flags);
  		return 0;
  	}
  	i = (int)find_first_bit(&port->write_urbs_free,
  						ARRAY_SIZE(port->write_urbs));
  	spin_unlock_irqrestore(&port->lock, flags);
  
  	urb = port->write_urbs[i];
  	count = port->serial->type->prepare_write_buffer(port,
  						urb->transfer_buffer,
  						port->bulk_out_size);
  	urb->transfer_buffer_length = count;
  	usb_serial_debug_data(&port->dev, __func__, count, urb->transfer_buffer);
  	spin_lock_irqsave(&port->lock, flags);
  	port->tx_bytes += count;
  	spin_unlock_irqrestore(&port->lock, flags);
  
  	clear_bit(i, &port->write_urbs_free);
  	result = usb_submit_urb(urb, mem_flags);
  	if (result) {
  		dev_err_console(port, "%s - error submitting urb: %d\n",
  						__func__, result);
  		set_bit(i, &port->write_urbs_free);
  		spin_lock_irqsave(&port->lock, flags);
  		port->tx_bytes -= count;
  		spin_unlock_irqrestore(&port->lock, flags);
  
  		clear_bit_unlock(USB_SERIAL_WRITE_BUSY, &port->flags);
  		return result;
  	}
  
  	goto retry;	/* try sending off another urb */
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_write_start);
  
  /**
   * usb_serial_generic_write - generic write function
   * @tty: tty for the port
   * @port: usb-serial port
   * @buf: data to write
   * @count: number of bytes to write
   *
   * Return: The number of characters buffered, which may be anything from
   * zero to @count, or a negative errno value.
   */
  int usb_serial_generic_write(struct tty_struct *tty,
  	struct usb_serial_port *port, const unsigned char *buf, int count)
  {
  	int result;
  
  	if (!port->bulk_out_size)
  		return -ENODEV;
  
  	if (!count)
  		return 0;
  
  	count = kfifo_in_locked(&port->write_fifo, buf, count, &port->lock);
  	result = usb_serial_generic_write_start(port, GFP_ATOMIC);
  	if (result)
  		return result;
  
  	return count;
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_write);
  
  int usb_serial_generic_write_room(struct tty_struct *tty)
  {
  	struct usb_serial_port *port = tty->driver_data;
  	unsigned long flags;
  	int room;
  
  	if (!port->bulk_out_size)
  		return 0;
  
  	spin_lock_irqsave(&port->lock, flags);
  	room = kfifo_avail(&port->write_fifo);
  	spin_unlock_irqrestore(&port->lock, flags);
  
  	dev_dbg(&port->dev, "%s - returns %d\n", __func__, room);
  	return room;
  }
  
  int usb_serial_generic_chars_in_buffer(struct tty_struct *tty)
  {
  	struct usb_serial_port *port = tty->driver_data;
  	unsigned long flags;
  	int chars;
  
  	if (!port->bulk_out_size)
  		return 0;
  
  	spin_lock_irqsave(&port->lock, flags);
  	chars = kfifo_len(&port->write_fifo) + port->tx_bytes;
  	spin_unlock_irqrestore(&port->lock, flags);
  
  	dev_dbg(&port->dev, "%s - returns %d\n", __func__, chars);
  	return chars;
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_chars_in_buffer);
  
  void usb_serial_generic_wait_until_sent(struct tty_struct *tty, long timeout)
  {
  	struct usb_serial_port *port = tty->driver_data;
  	unsigned int bps;
  	unsigned long period;
  	unsigned long expire;
  
  	bps = tty_get_baud_rate(tty);
  	if (!bps)
  		bps = 9600;	/* B0 */
  	/*
  	 * Use a poll-period of roughly the time it takes to send one
  	 * character or at least one jiffy.
  	 */
  	period = max_t(unsigned long, (10 * HZ / bps), 1);
  	if (timeout)
  		period = min_t(unsigned long, period, timeout);
  
  	dev_dbg(&port->dev, "%s - timeout = %u ms, period = %u ms\n",
  					__func__, jiffies_to_msecs(timeout),
  					jiffies_to_msecs(period));
  	expire = jiffies + timeout;
  	while (!port->serial->type->tx_empty(port)) {
  		schedule_timeout_interruptible(period);
  		if (signal_pending(current))
  			break;
  		if (timeout && time_after(jiffies, expire))
  			break;
  	}
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_wait_until_sent);
  
  static int usb_serial_generic_submit_read_urb(struct usb_serial_port *port,
  						int index, gfp_t mem_flags)
  {
  	int res;
  
  	if (!test_and_clear_bit(index, &port->read_urbs_free))
  		return 0;
  
  	dev_dbg(&port->dev, "%s - urb %d\n", __func__, index);
  
  	res = usb_submit_urb(port->read_urbs[index], mem_flags);
  	if (res) {
  		if (res != -EPERM && res != -ENODEV) {
  			dev_err(&port->dev,
  					"%s - usb_submit_urb failed: %d\n",
  					__func__, res);
  		}
  		set_bit(index, &port->read_urbs_free);
  		return res;
  	}
  
  	return 0;
  }
  
  int usb_serial_generic_submit_read_urbs(struct usb_serial_port *port,
  					gfp_t mem_flags)
  {
  	int res;
  	int i;
  
  	for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i) {
  		res = usb_serial_generic_submit_read_urb(port, i, mem_flags);
  		if (res)
  			goto err;
  	}
  
  	return 0;
  err:
  	for (; i >= 0; --i)
  		usb_kill_urb(port->read_urbs[i]);
  
  	return res;
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_submit_read_urbs);
  
  void usb_serial_generic_process_read_urb(struct urb *urb)
  {
  	struct usb_serial_port *port = urb->context;
  	char *ch = (char *)urb->transfer_buffer;
  	int i;
  
  	if (!urb->actual_length)
  		return;
  	/*
  	 * The per character mucking around with sysrq path it too slow for
  	 * stuff like 3G modems, so shortcircuit it in the 99.9999999% of
  	 * cases where the USB serial is not a console anyway.
  	 */
  	if (!port->port.console || !port->sysrq) {
  		tty_insert_flip_string(&port->port, ch, urb->actual_length);
  	} else {
  		for (i = 0; i < urb->actual_length; i++, ch++) {
  			if (!usb_serial_handle_sysrq_char(port, *ch))
  				tty_insert_flip_char(&port->port, *ch, TTY_NORMAL);
  		}
  	}
  	tty_flip_buffer_push(&port->port);
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_process_read_urb);
  
  void usb_serial_generic_read_bulk_callback(struct urb *urb)
  {
  	struct usb_serial_port *port = urb->context;
  	unsigned char *data = urb->transfer_buffer;
  	unsigned long flags;
  	int status = urb->status;
  	int i;
  
  	for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i) {
  		if (urb == port->read_urbs[i])
  			break;
  	}
  	set_bit(i, &port->read_urbs_free);
  
  	dev_dbg(&port->dev, "%s - urb %d, len %d\n", __func__, i,
  							urb->actual_length);
  	switch (status) {
  	case 0:
  		break;
  	case -ENOENT:
  	case -ECONNRESET:
  	case -ESHUTDOWN:
  		dev_dbg(&port->dev, "%s - urb stopped: %d\n",
  							__func__, status);
  		return;
  	case -EPIPE:
  		dev_err(&port->dev, "%s - urb stopped: %d\n",
  							__func__, status);
  		return;
  	default:
  		dev_dbg(&port->dev, "%s - nonzero urb status: %d\n",
  							__func__, status);
  		goto resubmit;
  	}
  
  	usb_serial_debug_data(&port->dev, __func__, urb->actual_length, data);
  	port->serial->type->process_read_urb(urb);
  
  resubmit:
  	/* Throttle the device if requested by tty */
  	spin_lock_irqsave(&port->lock, flags);
  	port->throttled = port->throttle_req;
  	if (!port->throttled) {
  		spin_unlock_irqrestore(&port->lock, flags);
  		usb_serial_generic_submit_read_urb(port, i, GFP_ATOMIC);
  	} else {
  		spin_unlock_irqrestore(&port->lock, flags);
  	}
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_read_bulk_callback);
  
  void usb_serial_generic_write_bulk_callback(struct urb *urb)
  {
  	unsigned long flags;
  	struct usb_serial_port *port = urb->context;
  	int status = urb->status;
  	int i;
  
  	for (i = 0; i < ARRAY_SIZE(port->write_urbs); ++i) {
  		if (port->write_urbs[i] == urb)
  			break;
  	}
  	spin_lock_irqsave(&port->lock, flags);
  	port->tx_bytes -= urb->transfer_buffer_length;
  	set_bit(i, &port->write_urbs_free);
  	spin_unlock_irqrestore(&port->lock, flags);
  
  	switch (status) {
  	case 0:
  		break;
  	case -ENOENT:
  	case -ECONNRESET:
  	case -ESHUTDOWN:
  		dev_dbg(&port->dev, "%s - urb stopped: %d\n",
  							__func__, status);
  		return;
  	case -EPIPE:
  		dev_err_console(port, "%s - urb stopped: %d\n",
  							__func__, status);
  		return;
  	default:
  		dev_err_console(port, "%s - nonzero urb status: %d\n",
  							__func__, status);
  		goto resubmit;
  	}
  
  resubmit:
  	usb_serial_generic_write_start(port, GFP_ATOMIC);
  	usb_serial_port_softint(port);
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_write_bulk_callback);
  
  void usb_serial_generic_throttle(struct tty_struct *tty)
  {
  	struct usb_serial_port *port = tty->driver_data;
  	unsigned long flags;
  
  	spin_lock_irqsave(&port->lock, flags);
  	port->throttle_req = 1;
  	spin_unlock_irqrestore(&port->lock, flags);
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_throttle);
  
  void usb_serial_generic_unthrottle(struct tty_struct *tty)
  {
  	struct usb_serial_port *port = tty->driver_data;
  	int was_throttled;
  
  	spin_lock_irq(&port->lock);
  	was_throttled = port->throttled;
  	port->throttled = port->throttle_req = 0;
  	spin_unlock_irq(&port->lock);
  
  	if (was_throttled)
  		usb_serial_generic_submit_read_urbs(port, GFP_KERNEL);
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_unthrottle);
  
  static bool usb_serial_generic_msr_changed(struct tty_struct *tty,
  				unsigned long arg, struct async_icount *cprev)
  {
  	struct usb_serial_port *port = tty->driver_data;
  	struct async_icount cnow;
  	unsigned long flags;
  	bool ret;
  
  	/*
  	 * Use tty-port initialised flag to detect all hangups including the
  	 * one generated at USB-device disconnect.
  	 */
  	if (!tty_port_initialized(&port->port))
  		return true;
  
  	spin_lock_irqsave(&port->lock, flags);
  	cnow = port->icount;				/* atomic copy*/
  	spin_unlock_irqrestore(&port->lock, flags);
  
  	ret =	((arg & TIOCM_RNG) && (cnow.rng != cprev->rng)) ||
  		((arg & TIOCM_DSR) && (cnow.dsr != cprev->dsr)) ||
  		((arg & TIOCM_CD)  && (cnow.dcd != cprev->dcd)) ||
  		((arg & TIOCM_CTS) && (cnow.cts != cprev->cts));
  
  	*cprev = cnow;
  
  	return ret;
  }
  
  int usb_serial_generic_tiocmiwait(struct tty_struct *tty, unsigned long arg)
  {
  	struct usb_serial_port *port = tty->driver_data;
  	struct async_icount cnow;
  	unsigned long flags;
  	int ret;
  
  	spin_lock_irqsave(&port->lock, flags);
  	cnow = port->icount;				/* atomic copy */
  	spin_unlock_irqrestore(&port->lock, flags);
  
  	ret = wait_event_interruptible(port->port.delta_msr_wait,
  			usb_serial_generic_msr_changed(tty, arg, &cnow));
  	if (!ret && !tty_port_initialized(&port->port))
  		ret = -EIO;
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_tiocmiwait);
  
  int usb_serial_generic_get_icount(struct tty_struct *tty,
  					struct serial_icounter_struct *icount)
  {
  	struct usb_serial_port *port = tty->driver_data;
  	struct async_icount cnow;
  	unsigned long flags;
  
  	spin_lock_irqsave(&port->lock, flags);
  	cnow = port->icount;				/* atomic copy */
  	spin_unlock_irqrestore(&port->lock, flags);
  
  	icount->cts = cnow.cts;
  	icount->dsr = cnow.dsr;
  	icount->rng = cnow.rng;
  	icount->dcd = cnow.dcd;
  	icount->tx = cnow.tx;
  	icount->rx = cnow.rx;
  	icount->frame = cnow.frame;
  	icount->parity = cnow.parity;
  	icount->overrun = cnow.overrun;
  	icount->brk = cnow.brk;
  	icount->buf_overrun = cnow.buf_overrun;
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_get_icount);
  
  #ifdef CONFIG_MAGIC_SYSRQ
  int usb_serial_handle_sysrq_char(struct usb_serial_port *port, unsigned int ch)
  {
  	if (port->sysrq && port->port.console) {
  		if (ch && time_before(jiffies, port->sysrq)) {
  			handle_sysrq(ch);
  			port->sysrq = 0;
  			return 1;
  		}
  		port->sysrq = 0;
  	}
  	return 0;
  }
  #else
  int usb_serial_handle_sysrq_char(struct usb_serial_port *port, unsigned int ch)
  {
  	return 0;
  }
  #endif
  EXPORT_SYMBOL_GPL(usb_serial_handle_sysrq_char);
  
  int usb_serial_handle_break(struct usb_serial_port *port)
  {
  	if (!port->sysrq) {
  		port->sysrq = jiffies + HZ*5;
  		return 1;
  	}
  	port->sysrq = 0;
  	return 0;
  }
  EXPORT_SYMBOL_GPL(usb_serial_handle_break);
  
  /**
   * usb_serial_handle_dcd_change - handle a change of carrier detect state
   * @port: usb-serial port
   * @tty: tty for the port
   * @status: new carrier detect status, nonzero if active
   */
  void usb_serial_handle_dcd_change(struct usb_serial_port *usb_port,
  				struct tty_struct *tty, unsigned int status)
  {
  	struct tty_port *port = &usb_port->port;
  
  	dev_dbg(&usb_port->dev, "%s - status %d\n", __func__, status);
  
  	if (tty) {
  		struct tty_ldisc *ld = tty_ldisc_ref(tty);
  
  		if (ld) {
  			if (ld->ops->dcd_change)
  				ld->ops->dcd_change(tty, status);
  			tty_ldisc_deref(ld);
  		}
  	}
  
  	if (status)
  		wake_up_interruptible(&port->open_wait);
  	else if (tty && !C_CLOCAL(tty))
  		tty_hangup(tty);
  }
  EXPORT_SYMBOL_GPL(usb_serial_handle_dcd_change);
  
  int usb_serial_generic_resume(struct usb_serial *serial)
  {
  	struct usb_serial_port *port;
  	int i, c = 0, r;
  
  	for (i = 0; i < serial->num_ports; i++) {
  		port = serial->port[i];
  		if (!tty_port_initialized(&port->port))
  			continue;
  
  		if (port->bulk_in_size) {
  			r = usb_serial_generic_submit_read_urbs(port,
  								GFP_NOIO);
  			if (r < 0)
  				c++;
  		}
  
  		if (port->bulk_out_size) {
  			r = usb_serial_generic_write_start(port, GFP_NOIO);
  			if (r < 0)
  				c++;
  		}
  	}
  
  	return c ? -EIO : 0;
  }
  EXPORT_SYMBOL_GPL(usb_serial_generic_resume);
  