ftdi_sio.c

	if (priv->interface) {	/* FT2232C */
		urb_index = (__u16)((urb_index << 8) | priv->interface);
	}

	rv = usb_control_msg(port->serial->dev,
			    usb_sndctrlpipe(port->serial->dev, 0),
			    FTDI_SIO_SET_BAUDRATE_REQUEST,
			    FTDI_SIO_SET_BAUDRATE_REQUEST_TYPE,
			    urb_value, urb_index,
			    buf, 0, WDR_SHORT_TIMEOUT);

	kfree(buf);
	return rv;
}



static int get_serial_info(struct usb_serial_port *port,
				struct serial_struct __user *retinfo)
{
	struct ftdi_private *priv = usb_get_serial_port_data(port);
	struct serial_struct tmp;

	if (!retinfo)
		return -EFAULT;
	memset(&tmp, 0, sizeof(tmp));
	tmp.flags = priv->flags;
	tmp.baud_base = priv->baud_base;
	tmp.custom_divisor = priv->custom_divisor;
	if (copy_to_user(retinfo, &tmp, sizeof(*retinfo)))
		return -EFAULT;
	return 0;
} /* get_serial_info */


static int set_serial_info(struct tty_struct *tty,
	struct usb_serial_port *port, struct serial_struct __user *newinfo)
{ /* set_serial_info */
	struct ftdi_private *priv = usb_get_serial_port_data(port);
	struct serial_struct new_serial;
	struct ftdi_private old_priv;

	if (copy_from_user(&new_serial, newinfo, sizeof(new_serial)))
		return -EFAULT;
	old_priv = *priv;

	/* Do error checking and permission checking */

	if (!capable(CAP_SYS_ADMIN)) {
		if (((new_serial.flags & ~ASYNC_USR_MASK) !=
		     (priv->flags & ~ASYNC_USR_MASK)))
			return -EPERM;
		priv->flags = ((priv->flags & ~ASYNC_USR_MASK) |
			       (new_serial.flags & ASYNC_USR_MASK));
		priv->custom_divisor = new_serial.custom_divisor;
		goto check_and_exit;
	}

	if ((new_serial.baud_base != priv->baud_base) &&
	    (new_serial.baud_base < 9600))
		return -EINVAL;

	/* Make the changes - these are privileged changes! */

	priv->flags = ((priv->flags & ~ASYNC_FLAGS) |
					(new_serial.flags & ASYNC_FLAGS));
	priv->custom_divisor = new_serial.custom_divisor;

	tty->low_latency = (priv->flags & ASYNC_LOW_LATENCY) ? 1 : 0;

check_and_exit:
	if ((old_priv.flags & ASYNC_SPD_MASK) !=
	     (priv->flags & ASYNC_SPD_MASK)) {
		if ((priv->flags & ASYNC_SPD_MASK) == ASYNC_SPD_HI)
			tty->alt_speed = 57600;
		else if ((priv->flags & ASYNC_SPD_MASK) == ASYNC_SPD_VHI)
			tty->alt_speed = 115200;
		else if ((priv->flags & ASYNC_SPD_MASK) == ASYNC_SPD_SHI)
			tty->alt_speed = 230400;
		else if ((priv->flags & ASYNC_SPD_MASK) == ASYNC_SPD_WARP)
			tty->alt_speed = 460800;
		else
			tty->alt_speed = 0;
	}
	if (((old_priv.flags & ASYNC_SPD_MASK) !=
	     (priv->flags & ASYNC_SPD_MASK)) ||
	    (((priv->flags & ASYNC_SPD_MASK) == ASYNC_SPD_CUST) &&
	     (old_priv.custom_divisor != priv->custom_divisor))) {
		change_speed(tty, port);
	}
	return 0;

} /* set_serial_info */


/* Determine type of FTDI chip based on USB config and descriptor. */
static void ftdi_determine_type(struct usb_serial_port *port)
{
	struct ftdi_private *priv = usb_get_serial_port_data(port);
	struct usb_serial *serial = port->serial;
	struct usb_device *udev = serial->dev;
	unsigned version;
	unsigned interfaces;

	/* Assume it is not the original SIO device for now. */
	priv->baud_base = 48000000 / 2;
	priv->write_offset = 0;

	version = le16_to_cpu(udev->descriptor.bcdDevice);
	interfaces = udev->actconfig->desc.bNumInterfaces;
	dbg("%s: bcdDevice = 0x%x, bNumInterfaces = %u", __func__,
			version, interfaces);
	if (interfaces > 1) {
		int inter;

		/* Multiple interfaces.  Assume FT2232C. */
		priv->chip_type = FT2232C;
		/* Determine interface code. */
		inter = serial->interface->altsetting->desc.bInterfaceNumber;
		if (inter == 0)
			priv->interface = PIT_SIOA;
		else
			priv->interface = PIT_SIOB;
		/* BM-type devices have a bug where bcdDevice gets set
		 * to 0x200 when iSerialNumber is 0.  */
		if (version < 0x500) {
			dbg("%s: something fishy - bcdDevice too low for multi-interface device",
					__func__);
		}
	} else if (version < 0x200) {
		/* Old device.  Assume its the original SIO. */
		priv->chip_type = SIO;
		priv->baud_base = 12000000 / 16;
		priv->write_offset = 1;
	} else if (version < 0x400) {
		/* Assume its an FT8U232AM (or FT8U245AM) */
		/* (It might be a BM because of the iSerialNumber bug,
		 * but it will still work as an AM device.) */
		priv->chip_type = FT8U232AM;
	} else if (version < 0x600) {
		/* Assume its an FT232BM (or FT245BM) */
		priv->chip_type = FT232BM;
	} else {
		/* Assume its an FT232R  */
		priv->chip_type = FT232RL;
	}
	info("Detected %s", ftdi_chip_name[priv->chip_type]);
}


/*
 * ***************************************************************************
 * Sysfs Attribute
 * ***************************************************************************
 */

static ssize_t show_latency_timer(struct device *dev,
				struct device_attribute *attr, char *buf)
{
	struct usb_serial_port *port = to_usb_serial_port(dev);
	struct ftdi_private *priv = usb_get_serial_port_data(port);
	struct usb_device *udev = port->serial->dev;
	unsigned short latency = 0;
	int rv = 0;


	dbg("%s", __func__);

	rv = usb_control_msg(udev,
			     usb_rcvctrlpipe(udev, 0),
			     FTDI_SIO_GET_LATENCY_TIMER_REQUEST,
			     FTDI_SIO_GET_LATENCY_TIMER_REQUEST_TYPE,
			     0, priv->interface,
			     (char *) &latency, 1, WDR_TIMEOUT);

	if (rv < 0) {
		dev_err(dev, "Unable to read latency timer: %i\n", rv);
		return -EIO;
	}
	return sprintf(buf, "%i\n", latency);
}

/* Write a new value of the latency timer, in units of milliseconds. */
static ssize_t store_latency_timer(struct device *dev,
			struct device_attribute *attr, const char *valbuf,
			size_t count)
{
	struct usb_serial_port *port = to_usb_serial_port(dev);
	struct ftdi_private *priv = usb_get_serial_port_data(port);
	struct usb_device *udev = port->serial->dev;
	char buf[1];
	int v = simple_strtoul(valbuf, NULL, 10);
	int rv = 0;

	dbg("%s: setting latency timer = %i", __func__, v);

	rv = usb_control_msg(udev,
			     usb_sndctrlpipe(udev, 0),
			     FTDI_SIO_SET_LATENCY_TIMER_REQUEST,
			     FTDI_SIO_SET_LATENCY_TIMER_REQUEST_TYPE,
			     v, priv->interface,
			     buf, 0, WDR_TIMEOUT);

	if (rv < 0) {
		dev_err(dev, "Unable to write latency timer: %i\n", rv);
		return -EIO;
	}

	return count;
}

/* Write an event character directly to the FTDI register.  The ASCII
   value is in the low 8 bits, with the enable bit in the 9th bit. */
static ssize_t store_event_char(struct device *dev,
	struct device_attribute *attr, const char *valbuf, size_t count)
{
	struct usb_serial_port *port = to_usb_serial_port(dev);
	struct ftdi_private *priv = usb_get_serial_port_data(port);
	struct usb_device *udev = port->serial->dev;
	char buf[1];
	int v = simple_strtoul(valbuf, NULL, 10);
	int rv = 0;

	dbg("%s: setting event char = %i", __func__, v);

	rv = usb_control_msg(udev,
			     usb_sndctrlpipe(udev, 0),
			     FTDI_SIO_SET_EVENT_CHAR_REQUEST,
			     FTDI_SIO_SET_EVENT_CHAR_REQUEST_TYPE,
			     v, priv->interface,
			     buf, 0, WDR_TIMEOUT);

	if (rv < 0) {
		dbg("Unable to write event character: %i", rv);
		return -EIO;
	}

	return count;
}

static DEVICE_ATTR(latency_timer, S_IWUSR | S_IRUGO, show_latency_timer,
							store_latency_timer);
static DEVICE_ATTR(event_char, S_IWUSR, NULL, store_event_char);

static int create_sysfs_attrs(struct usb_serial_port *port)
{
	struct ftdi_private *priv = usb_get_serial_port_data(port);
	int retval = 0;

	dbg("%s", __func__);

	/* XXX I've no idea if the original SIO supports the event_char
	 * sysfs parameter, so I'm playing it safe.  */
	if (priv->chip_type != SIO) {
		dbg("sysfs attributes for %s", ftdi_chip_name[priv->chip_type]);
		retval = device_create_file(&port->dev, &dev_attr_event_char);
		if ((!retval) &&
		    (priv->chip_type == FT232BM ||
		     priv->chip_type == FT2232C ||
		     priv->chip_type == FT232RL)) {
			retval = device_create_file(&port->dev,
						    &dev_attr_latency_timer);
		}
	}
	return retval;
}

static void remove_sysfs_attrs(struct usb_serial_port *port)
{
	struct ftdi_private *priv = usb_get_serial_port_data(port);

	dbg("%s", __func__);

	/* XXX see create_sysfs_attrs */
	if (priv->chip_type != SIO) {
		device_remove_file(&port->dev, &dev_attr_event_char);
		if (priv->chip_type == FT232BM ||
		    priv->chip_type == FT2232C ||
		    priv->chip_type == FT232RL) {
			device_remove_file(&port->dev, &dev_attr_latency_timer);
		}
	}

}

/*
 * ***************************************************************************
 * FTDI driver specific functions
 * ***************************************************************************
 */

/* Probe function to check for special devices */
static int ftdi_sio_probe(struct usb_serial *serial,
					const struct usb_device_id *id)
{
	struct ftdi_sio_quirk *quirk =
				(struct ftdi_sio_quirk *)id->driver_info;

	if (quirk && quirk->probe) {
		int ret = quirk->probe(serial);
		if (ret != 0)
			return ret;
	}

	usb_set_serial_data(serial, (void *)id->driver_info);

	return 0;
}

static int ftdi_sio_port_probe(struct usb_serial_port *port)
{
	struct ftdi_private *priv;
	struct ftdi_sio_quirk *quirk = usb_get_serial_data(port->serial);


	dbg("%s", __func__);

	priv = kzalloc(sizeof(struct ftdi_private), GFP_KERNEL);
	if (!priv) {
		err("%s- kmalloc(%Zd) failed.", __func__,
					sizeof(struct ftdi_private));
		return -ENOMEM;
	}

	spin_lock_init(&priv->rx_lock);
	spin_lock_init(&priv->tx_lock);
	init_waitqueue_head(&priv->delta_msr_wait);
	/* This will push the characters through immediately rather
	   than queue a task to deliver them */
	priv->flags = ASYNC_LOW_LATENCY;

	if (quirk && quirk->port_probe)
		quirk->port_probe(priv);

	/* Increase the size of read buffers */
	kfree(port->bulk_in_buffer);
	port->bulk_in_buffer = kmalloc(BUFSZ, GFP_KERNEL);
	if (!port->bulk_in_buffer) {
		kfree(priv);
		return -ENOMEM;
	}
	if (port->read_urb) {
		port->read_urb->transfer_buffer = port->bulk_in_buffer;
		port->read_urb->transfer_buffer_length = BUFSZ;
	}

	INIT_DELAYED_WORK(&priv->rx_work, ftdi_process_read);
	priv->port = port;

	/* Free port's existing write urb and transfer buffer. */
	if (port->write_urb) {
		usb_free_urb(port->write_urb);
		port->write_urb = NULL;
	}
	kfree(port->bulk_out_buffer);
	port->bulk_out_buffer = NULL;

	usb_set_serial_port_data(port, priv);

	ftdi_determine_type(port);
	create_sysfs_attrs(port);
	return 0;
}

/* Setup for the USB-UIRT device, which requires hardwired
 * baudrate (38400 gets mapped to 312500) */
/* Called from usbserial:serial_probe */
static void ftdi_USB_UIRT_setup(struct ftdi_private *priv)
{
	dbg("%s", __func__);

	priv->flags |= ASYNC_SPD_CUST;
	priv->custom_divisor = 77;
	priv->force_baud = 38400;
} /* ftdi_USB_UIRT_setup */

/* Setup for the HE-TIRA1 device, which requires hardwired
 * baudrate (38400 gets mapped to 100000) and RTS-CTS enabled.  */

static void ftdi_HE_TIRA1_setup(struct ftdi_private *priv)
{
	dbg("%s", __func__);

	priv->flags |= ASYNC_SPD_CUST;
	priv->custom_divisor = 240;
	priv->force_baud = 38400;
	priv->force_rtscts = 1;
} /* ftdi_HE_TIRA1_setup */

/*
 * First port on JTAG adaptors such as Olimex arm-usb-ocd or the FIC/OpenMoko
 * Neo1973 Debug Board is reserved for JTAG interface and can be accessed from
 * userspace using openocd.
 */
static int ftdi_jtag_probe(struct usb_serial *serial)
{
	struct usb_device *udev = serial->dev;
	struct usb_interface *interface = serial->interface;

	dbg("%s", __func__);

	if (interface == udev->actconfig->interface[0]) {
		info("Ignoring serial port reserved for JTAG");
		return -ENODEV;
	}

	return 0;
}

/*
 * The Matrix Orbital VK204-25-USB has an invalid IN endpoint.
 * We have to correct it if we want to read from it.
 */
static int ftdi_mtxorb_hack_setup(struct usb_serial *serial)
{
	struct usb_host_endpoint *ep = serial->dev->ep_in[1];
	struct usb_endpoint_descriptor *ep_desc = &ep->desc;

	if (ep->enabled && ep_desc->wMaxPacketSize == 0) {
		ep_desc->wMaxPacketSize = cpu_to_le16(0x40);
		info("Fixing invalid wMaxPacketSize on read pipe");
	}

	return 0;
}

/* ftdi_shutdown is called from usbserial:usb_serial_disconnect
 *   it is called when the usb device is disconnected
 *
 *   usbserial:usb_serial_disconnect
 *      calls __serial_close for each open of the port
 *      shutdown is called then (ie ftdi_shutdown)
 */
static void ftdi_shutdown(struct usb_serial *serial)
{
	dbg("%s", __func__);
}

static int ftdi_sio_port_remove(struct usb_serial_port *port)
{
	struct ftdi_private *priv = usb_get_serial_port_data(port);

	dbg("%s", __func__);

	remove_sysfs_attrs(port);

	/* all open ports are closed at this point
	 *    (by usbserial.c:__serial_close, which calls ftdi_close)
	 */

	if (priv) {
		usb_set_serial_port_data(port, NULL);
		kfree(priv);
	}

	return 0;
}

static int ftdi_open(struct tty_struct *tty,
			struct usb_serial_port *port, struct file *filp)
{ /* ftdi_open */
	struct usb_device *dev = port->serial->dev;
	struct ftdi_private *priv = usb_get_serial_port_data(port);
	unsigned long flags;

	int result = 0;
	char buf[1]; /* Needed for the usb_control_msg I think */

	dbg("%s", __func__);

	spin_lock_irqsave(&priv->tx_lock, flags);
	priv->tx_bytes = 0;
	spin_unlock_irqrestore(&priv->tx_lock, flags);
	spin_lock_irqsave(&priv->rx_lock, flags);
	priv->rx_bytes = 0;
	spin_unlock_irqrestore(&priv->rx_lock, flags);

	if (tty)
		tty->low_latency = (priv->flags & ASYNC_LOW_LATENCY) ? 1 : 0;

	/* No error checking for this (will get errors later anyway) */
	/* See ftdi_sio.h for description of what is reset */
	usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
			FTDI_SIO_RESET_REQUEST, FTDI_SIO_RESET_REQUEST_TYPE,
			FTDI_SIO_RESET_SIO,
			priv->interface, buf, 0, WDR_TIMEOUT);

	/* Termios defaults are set by usb_serial_init. We don't change
	   port->tty->termios - this would loose speed settings, etc.
	   This is same behaviour as serial.c/rs_open() - Kuba */

	/* ftdi_set_termios  will send usb control messages */
	if (tty)
		ftdi_set_termios(tty, port, tty->termios);

	/* FIXME: Flow control might be enabled, so it should be checked -
	   we have no control of defaults! */
	/* Turn on RTS and DTR since we are not flow controlling by default */
	set_mctrl(port, TIOCM_DTR | TIOCM_RTS);

	/* Not throttled */
	spin_lock_irqsave(&priv->rx_lock, flags);
	priv->rx_flags &= ~(THROTTLED | ACTUALLY_THROTTLED);
	spin_unlock_irqrestore(&priv->rx_lock, flags);

	/* Start reading from the device */
	priv->rx_processed = 0;
	usb_fill_bulk_urb(port->read_urb, dev,
			usb_rcvbulkpipe(dev, port->bulk_in_endpointAddress),
			port->read_urb->transfer_buffer,
				port->read_urb->transfer_buffer_length,
			ftdi_read_bulk_callback, port);
	result = usb_submit_urb(port->read_urb, GFP_KERNEL);
	if (result)
		err("%s - failed submitting read urb, error %d",
							__func__, result);


	return result;
} /* ftdi_open */



/*
 * usbserial:__serial_close  only calls ftdi_close if the point is open
 *
 *   This only gets called when it is the last close
 *
 *
 */

static void ftdi_close(struct tty_struct *tty,
			struct usb_serial_port *port, struct file *filp)
{ /* ftdi_close */
	unsigned int c_cflag = tty->termios->c_cflag;
	struct ftdi_private *priv = usb_get_serial_port_data(port);
	char buf[1];

	dbg("%s", __func__);

	mutex_lock(&port->serial->disc_mutex);
	if (c_cflag & HUPCL && !port->serial->disconnected) {
		/* Disable flow control */
		if (usb_control_msg(port->serial->dev,
				    usb_sndctrlpipe(port->serial->dev, 0),
				    FTDI_SIO_SET_FLOW_CTRL_REQUEST,
				    FTDI_SIO_SET_FLOW_CTRL_REQUEST_TYPE,
				    0, priv->interface, buf, 0,
				    WDR_TIMEOUT) < 0) {
			err("error from flowcontrol urb");
		}

		/* drop RTS and DTR */
		clear_mctrl(port, TIOCM_DTR | TIOCM_RTS);
	} /* Note change no line if hupcl is off */
	mutex_unlock(&port->serial->disc_mutex);

	/* cancel any scheduled reading */
	cancel_delayed_work(&priv->rx_work);
	flush_scheduled_work();

	/* shutdown our bulk read */
	usb_kill_urb(port->read_urb);
} /* ftdi_close */



/* The SIO requires the first byte to have:
 *  B0 1
 *  B1 0
 *  B2..7 length of message excluding byte 0
 *
 * The new devices do not require this byte
 */
static int ftdi_write(struct tty_struct *tty, struct usb_serial_port *port,
			   const unsigned char *buf, int count)
{ /* ftdi_write */
	struct ftdi_private *priv = usb_get_serial_port_data(port);
	struct urb *urb;
	unsigned char *buffer;
	int data_offset ;       /* will be 1 for the SIO and 0 otherwise */
	int status;
	int transfer_size;
	unsigned long flags;

	dbg("%s port %d, %d bytes", __func__, port->number, count);

	if (count == 0) {
		dbg("write request of 0 bytes");
		return 0;
	}
	spin_lock_irqsave(&priv->tx_lock, flags);
	if (priv->tx_outstanding_urbs > URB_UPPER_LIMIT) {
		spin_unlock_irqrestore(&priv->tx_lock, flags);
		dbg("%s - write limit hit\n", __func__);
		return 0;
	}
	priv->tx_outstanding_urbs++;
	spin_unlock_irqrestore(&priv->tx_lock, flags);

	data_offset = priv->write_offset;
	dbg("data_offset set to %d", data_offset);

	/* Determine total transfer size */
	transfer_size = count;
	if (data_offset > 0) {
		/* Original sio needs control bytes too... */
		transfer_size += (data_offset *
				((count + (PKTSZ - 1 - data_offset)) /
				 (PKTSZ - data_offset)));
	}

	buffer = kmalloc(transfer_size, GFP_ATOMIC);
	if (!buffer) {
		err("%s ran out of kernel memory for urb ...", __func__);
		count = -ENOMEM;
		goto error_no_buffer;
	}

	urb = usb_alloc_urb(0, GFP_ATOMIC);
	if (!urb) {
		err("%s - no more free urbs", __func__);
		count = -ENOMEM;
		goto error_no_urb;
	}

	/* Copy data */
	if (data_offset > 0) {
		/* Original sio requires control byte at start of
		   each packet. */
		int user_pktsz = PKTSZ - data_offset;
		int todo = count;
		unsigned char *first_byte = buffer;
		const unsigned char *current_position = buf;

		while (todo > 0) {
			if (user_pktsz > todo)
				user_pktsz = todo;
			/* Write the control byte at the front of the packet*/
			*first_byte = 1 | ((user_pktsz) << 2);
			/* Copy data for packet */
			memcpy(first_byte + data_offset,
				current_position, user_pktsz);
			first_byte += user_pktsz + data_offset;
			current_position += user_pktsz;
			todo -= user_pktsz;
		}
	} else {
		/* No control byte required. */
		/* Copy in the data to send */
		memcpy(buffer, buf, count);
	}

	usb_serial_debug_data(debug, &port->dev, __func__,
						transfer_size, buffer);

	/* fill the buffer and send it */
	usb_fill_bulk_urb(urb, port->serial->dev,
			usb_sndbulkpipe(port->serial->dev,
					port->bulk_out_endpointAddress),
			buffer, transfer_size,
			ftdi_write_bulk_callback, port);

	status = usb_submit_urb(urb, GFP_ATOMIC);
	if (status) {
		err("%s - failed submitting write urb, error %d",
							__func__, status);
		count = status;
		goto error;
	} else {
		spin_lock_irqsave(&priv->tx_lock, flags);
		priv->tx_outstanding_bytes += count;
		priv->tx_bytes += count;
		spin_unlock_irqrestore(&priv->tx_lock, flags);
	}

	/* we are done with this urb, so let the host driver
	 * really free it when it is finished with it */
	usb_free_urb(urb);

	dbg("%s write returning: %d", __func__, count);
	return count;
error:
	usb_free_urb(urb);
error_no_urb:
	kfree(buffer);
error_no_buffer:
	spin_lock_irqsave(&priv->tx_lock, flags);
	priv->tx_outstanding_urbs--;
	spin_unlock_irqrestore(&priv->tx_lock, flags);
	return count;
} /* ftdi_write */


/* This function may get called when the device is closed */

static void ftdi_write_bulk_callback(struct urb *urb)
{
	unsigned long flags;
	struct usb_serial_port *port = urb->context;
	struct ftdi_private *priv;
	int data_offset;       /* will be 1 for the SIO and 0 otherwise */
	unsigned long countback;
	int status = urb->status;

	/* free up the transfer buffer, as usb_free_urb() does not do this */
	kfree(urb->transfer_buffer);

	dbg("%s - port %d", __func__, port->number);

	if (status) {
		dbg("nonzero write bulk status received: %d", status);
		return;
	}

	priv = usb_get_serial_port_data(port);
	if (!priv) {
		dbg("%s - bad port private data pointer - exiting", __func__);
		return;
	}
	/* account for transferred data */
	countback = urb->actual_length;
	data_offset = priv->write_offset;
	if (data_offset > 0) {
		/* Subtract the control bytes */
		countback -= (data_offset * DIV_ROUND_UP(countback, PKTSZ));
	}
	spin_lock_irqsave(&priv->tx_lock, flags);
	--priv->tx_outstanding_urbs;
	priv->tx_outstanding_bytes -= countback;
	spin_unlock_irqrestore(&priv->tx_lock, flags);

	usb_serial_port_softint(port);
} /* ftdi_write_bulk_callback */


static int ftdi_write_room(struct tty_struct *tty)
{
	struct usb_serial_port *port = tty->driver_data;
	struct ftdi_private *priv = usb_get_serial_port_data(port);
	int room;
	unsigned long flags;

	dbg("%s - port %d", __func__, port->number);

	spin_lock_irqsave(&priv->tx_lock, flags);
	if (priv->tx_outstanding_urbs < URB_UPPER_LIMIT) {
		/*
		 * We really can take anything the user throws at us
		 * but let's pick a nice big number to tell the tty
		 * layer that we have lots of free space
		 */
		room = 2048;
	} else {
		room = 0;
	}
	spin_unlock_irqrestore(&priv->tx_lock, flags);
	return room;
}

static int ftdi_chars_in_buffer(struct tty_struct *tty)
{
	struct usb_serial_port *port = tty->driver_data;
	struct ftdi_private *priv = usb_get_serial_port_data(port);
	int buffered;
	unsigned long flags;

	dbg("%s - port %d", __func__, port->number);

	spin_lock_irqsave(&priv->tx_lock, flags);
	buffered = (int)priv->tx_outstanding_bytes;
	spin_unlock_irqrestore(&priv->tx_lock, flags);
	if (buffered < 0) {
		err("%s outstanding tx bytes is negative!", __func__);
		buffered = 0;
	}
	return buffered;
}

static void ftdi_read_bulk_callback(struct urb *urb)
{
	struct usb_serial_port *port = urb->context;
	struct tty_struct *tty;
	struct ftdi_private *priv;
	unsigned long countread;
	unsigned long flags;
	int status = urb->status;

	if (urb->number_of_packets > 0) {
		err("%s transfer_buffer_length %d actual_length %d number of packets %d",
				__func__,
				urb->transfer_buffer_length,
				urb->actual_length, urb->number_of_packets);
		err("%s transfer_flags %x ", __func__, urb->transfer_flags);
	}

	dbg("%s - port %d", __func__, port->number);

	if (port->port.count <= 0)
		return;

	tty = port->port.tty;
	if (!tty) {
		dbg("%s - bad tty pointer - exiting", __func__);
		return;
	}

	priv = usb_get_serial_port_data(port);
	if (!priv) {
		dbg("%s - bad port private data pointer - exiting", __func__);
		return;
	}

	if (urb != port->read_urb)
		err("%s - Not my urb!", __func__);

	if (status) {
		/* This will happen at close every time so it is a dbg not an
		   err */
		dbg("(this is ok on close) nonzero read bulk status received: %d", status);
		return;
	}

	/* count data bytes, but not status bytes */
	countread = urb->actual_length;
	countread -= 2 * DIV_ROUND_UP(countread, PKTSZ);
	spin_lock_irqsave(&priv->rx_lock, flags);
	priv->rx_bytes += countread;
	spin_unlock_irqrestore(&priv->rx_lock, flags);

	ftdi_process_read(&priv->rx_work.work);

} /* ftdi_read_bulk_callback */


static void ftdi_process_read(struct work_struct *work)
{ /* ftdi_process_read */
	struct ftdi_private *priv =
		container_of(work, struct ftdi_private, rx_work.work);
	struct usb_serial_port *port = priv->port;
	struct urb *urb;
	struct tty_struct *tty;
	char error_flag;
	unsigned char *data;

	int i;
	int result;
	int need_flip;
	int packet_offset;
	unsigned long flags;

	dbg("%s - port %d", __func__, port->number);

	if (port->port.count <= 0)
		return;

	tty = port->port.tty;
	if (!tty) {
		dbg("%s - bad tty pointer - exiting", __func__);
		return;
	}

	priv = usb_get_serial_port_data(port);
	if (!priv) {
		dbg("%s - bad port private data pointer - exiting", __func__);
		return;
	}

	urb = port->read_urb;
	if (!urb) {
		dbg("%s - bad read_urb pointer - exiting", __func__);
		return;
	}

	data = urb->transfer_buffer;

	if (priv->rx_processed) {
		dbg("%s - already processed: %d bytes, %d remain", __func__,
				priv->rx_processed,
				urb->actual_length - priv->rx_processed);
	} else {
		/* The first two bytes of every read packet are status */
		if (urb->actual_length > 2)
			usb_serial_debug_data(debug, &port->dev, __func__,
						urb->actual_length, data);
		else
			dbg("Status only: %03oo %03oo", data[0], data[1]);
	}


	/* TO DO -- check for hung up line and handle appropriately: */
	/*   send hangup  */
	/* See acm.c - you do a tty_hangup  - eg tty_hangup(tty) */
	/* if CD is dropped and the line is not CLOCAL then we should hangup */

	need_flip = 0;
	for (packet_offset = priv->rx_processed;
		packet_offset < urb->actual_length; packet_offset += PKTSZ) {
		int length;

		/* Compare new line status to the old one, signal if different/
		   N.B. packet may be processed more than once, but differences
		   are only processed once.  */
		if (priv != NULL) {
			char new_status = data[packet_offset + 0] &
							FTDI_STATUS_B0_MASK;
			if (new_status != priv->prev_status) {
				priv->diff_status |=
					new_status ^ priv->prev_status;
				wake_up_interruptible(&priv->delta_msr_wait);
				priv->prev_status = new_status;
			}
		}

		length = min(PKTSZ, urb->actual_length-packet_offset)-2;
		if (length < 0) {
			err("%s - bad packet length: %d", __func__, length+2);
			length = 0;
		}

		if (priv->rx_flags & THROTTLED) {
			dbg("%s - throttled", __func__);
			break;
		}
		if (tty_buffer_request_room(tty, length) < length) {
			/* break out & wait for throttling/unthrottling to
			   happen */
			dbg("%s - receive room low", __func__);
			break;
		}

		/* Handle errors and break */
		error_flag = TTY_NORMAL;
		/* Although the device uses a bitmask and hence can have
		   multiple errors on a packet - the order here sets the
		   priority the error is returned to the tty layer  */

		if (data[packet_offset+1] & FTDI_RS_OE) {
			error_flag = TTY_OVERRUN;
			dbg("OVERRRUN error");
		}
		if (data[packet_offset+1] & FTDI_RS_BI) {
			error_flag = TTY_BREAK;
			dbg("BREAK received");
		}
		if (data[packet_offset+1] & FTDI_RS_PE) {
			error_flag = TTY_PARITY;
			dbg("PARITY error");
		}
		if (data[packet_offset+1] & FTDI_RS_FE) {
			error_flag = TTY_FRAME;
			dbg("FRAMING error");
		}
		if (length > 0) {
			for (i = 2; i < length+2; i++) {
				/* Note that the error flag is duplicated for
				   every character received since we don't know
				   which character it applied to */
				tty_insert_flip_char(tty,
					data[packet_offset + i], error_flag);
			}
			need_flip = 1;
		}

#ifdef NOT_CORRECT_BUT_KEEPING_IT_FOR_NOW
		/* if a parity error is detected you get status packets forever
		   until a character is sent without a parity error.
		   This doesn't work well since the application receives a
		   never ending stream of bad data - even though new data
		   hasn't been sent. Therefore I (bill) have taken this out.
		   However - this might make sense for framing errors and so on
		   so I am leaving the code in for now.
		*/
		else {
			if (error_flag != TTY_NORMAL) {
				dbg("error_flag is not normal");
				/* In this case it is just status - if that is
				   an error send a bad character */
				if (tty->flip.count >= TTY_FLIPBUF_SIZE)
					tty_flip_buffer_push(tty);
				tty_insert_flip_char(tty, 0xff, error_flag);
				need_flip = 1;
			}
		}
#endif
	} /* "for(packet_offset=0..." */

	/* Low latency */
	if (need_flip)
		tty_flip_buffer_push(tty);

	if (packet_offset < urb->actual_length) {
		/* not completely processed - record progress */
		priv->rx_processed = packet_offset;
		dbg("%s - incomplete, %d bytes processed, %d remain",
				__func__, packet_offset,
				urb->actual_length - packet_offset);
		/* check if we were throttled while processing */
		spin_lock_irqsave(&priv->rx_lock, flags);
		if (priv->rx_flags & THROTTLED) {