Staging: quatech_usb2: implement open functionality

Part two of the driver implementation has finally got done. It
implements the rest of open and the callback for reads from the box. I
seem to have finally found a structure that can be made to work, with a
single set of URBs for bulk read and write for the whole device, which
are used by all the ports. I've rationalised a few things, but there
will still be a lot of clean-up needed.

This one definitely can panic the kernel when a port is opened for
reading, but I'm off on holiday so I thought I'd post where I have got
to so far. I haven't tried to debug why it panics with a null pointer
dereference yet.

Signed-off-by: Richard Ash <richard@audacityteam.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 515 insertions, 69 deletions

diff --git a/drivers/staging/quatech_usb2/quatech_usb2.c b/drivers/staging/quatech_usb2/quatech_usb2.c
index 3544e7005404..0eaea2e7ce8a 100644
--- a/drivers/staging/quatech_usb2/quatech_usb2.c
+++ b/drivers/staging/quatech_usb2/quatech_usb2.c
@@ -38,6 +38,7 @@ static int debug;
 #define QU2BOXPWRON 0x8000		/* magic number to turn FPGA power on */
 #define QU2BOX232 0x40			/* RS232 mode on MEI devices */
 #define QU2BOXSPD9600 0x60		/* set speed to 9600 baud */
+#define FIFO_DEPTH 1024			/* size of hardware fifos */
 /* directions for USB transfers */
 #define USBD_TRANSFER_DIRECTION_IN    0xc0
 #define USBD_TRANSFER_DIRECTION_OUT   0x40
@@ -84,6 +85,12 @@ static int debug;
 #define SERIAL_LSR_FE       0x08
 #define SERIAL_LSR_BI       0x10
 
+/* handy macros for doing escape sequence parsing on data reads */
+#define THISCHAR	((unsigned char *)(urb->transfer_buffer))[i]
+#define NEXTCHAR	((unsigned char *)(urb->transfer_buffer))[i + 1]
+#define THIRDCHAR	((unsigned char *)(urb->transfer_buffer))[i + 2]
+#define FOURTHCHAR	((unsigned char *)(urb->transfer_buffer))[i + 3]
+#define FIFTHCHAR	((unsigned char *)(urb->transfer_buffer))[i + 4]
 
 static struct usb_device_id quausb2_id_table[] = {
 	{USB_DEVICE(USB_VENDOR_ID_QUATECH, QUATECH_SSU2_100)},
@@ -99,8 +106,6 @@ static struct usb_device_id quausb2_id_table[] = {
 MODULE_DEVICE_TABLE(usb, quausb2_id_table);
 
 /* custom structures we need go here */
-
-
 static struct usb_driver quausb2_usb_driver = {
 	.name = "quatech-usb2-serial",
 	.probe = usb_serial_probe,
@@ -109,10 +114,35 @@ static struct usb_driver quausb2_usb_driver = {
 	.no_dynamic_id = 1,
 };
 
-/* structure in which to keep all the messy stuff that this driver needs
- * alongside the usb_serial_port structure */
+/** structure in which to keep all the messy stuff that this driver needs
+ * alongside the usb_serial_port structure
+ * @param read_urb_busy Flag indicating that port->read_urb is in use
+ * @param close_pending flag indicating that this port is in the process of
+ * being closed.
+ * @param shadowLSR Last received state of the line status register, holds the
+ * value of the line status flags from the port
+ * @param shadowMSR Last received state of the modem status register, holds
+ * the value of the modem status received from the port
+ * @param xmit_pending_bytes Number of bytes waiting to be sent out of
+ * the serial port
+ * @param xmit_fifo_room_bytes free space available in the transmit fifo
+ * for this port on the box
+ * @param rcv_flush Flag indicating that a receive flush has been requested by
+ * the hardware.
+ * @param xmit_flush Flag indicating that a transmit flush has been requested by
+ * the hardware.
+ */
 struct quatech2_port {
 	int	magic;
+	bool	read_urb_busy;
+	bool	close_pending;
+	__u8	shadowLSR;
+	__u8	shadowMSR;
+	int	xmit_pending_bytes;
+	int	xmit_fifo_room_bytes;
+	char	rcv_flush;
+	char	xmit_flush;
+
 	char	active;		/* someone has this device open */
 	unsigned char		*xfer_to_tty_buffer;
 	wait_queue_head_t	wait;
@@ -120,20 +150,27 @@ struct quatech2_port {
 	struct semaphore	sem;	/* locks this structure */
 	__u8	shadowLCR;	/* last LCR value received */
 	__u8	shadowMCR;	/* last MCR value received */
-	__u8	shadowMSR;	/* last MSR value received */
-	__u8	shadowLSR;	/* last LSR value received */
-	char	open_ports;	/* ports open on whole device */
 	char	RxHolding;
-	char	Rcv_Flush;
-	char	Xmit_Flush;
-	char	closePending;
 	char	fifo_empty_flag;
-	int	xmit_pending_bytes;
-	int	xmit_fifo_room_bytes;
 	struct semaphore	pend_xmit_sem;	/* locks this structure */
 	spinlock_t lock;
 };
 
+/**
+ * Structure to hold device-wide internal status information
+ * @param ReadBulkStopped The last bulk read attempt ended in tears
+ * @param open_ports The number of serial ports currently in use on the box
+ * @param current_port Pointer to the serial port structure of the port which
+ * the read stream is currently directed to. Escape sequences in the read
+ * stream will change this around as data arrives from different ports on the
+ * box
+ */
+struct quatech2_dev {
+	bool	ReadBulkStopped;
+	char	open_ports;
+	struct usb_serial_port *current_port;
+};
+
 /* structure which holds line and modem status flags */
 struct qt2_status_data {
 	__u8 line_status;
@@ -152,12 +189,30 @@ static inline struct quatech2_port *qt2_get_port_private(struct usb_serial_port
 			*port);
 static inline void qt2_set_port_private(struct usb_serial_port *port,
 			struct quatech2_port *data);
+static inline struct quatech2_dev *qt2_get_dev_private(struct usb_serial
+			*serial);
+static inline void qt2_set_dev_private(struct usb_serial *serial,
+			struct quatech2_dev *data);
 static int qt2_openboxchannel(struct usb_serial *serial, __u16
 			Uart_Number, struct qt2_status_data *pDeviceData);
 static int qt2_closeboxchannel(struct usb_serial *serial, __u16
 			Uart_Number);
 static int qt2_conf_uart(struct usb_serial *serial,  unsigned short Uart_Number,
 			 unsigned short divisor, unsigned char LCR);
+static void qt2_read_bulk_callback(struct urb *urb);
+static void qt2_process_line_status(struct usb_serial_port *port,
+			      unsigned char LineStatus);
+static void qt2_process_modem_status(struct usb_serial_port *port,
+			       unsigned char ModemStatus);
+static void qt2_process_xmit_empty(struct usb_serial_port *port,
+	unsigned char fourth_char, unsigned char fifth_char);
+static void qt2_process_port_change(struct usb_serial_port *port,
+			      unsigned char New_Current_Port);
+static void qt2_process_rcv_flush(struct usb_serial_port *port);
+static void qt2_process_xmit_flush(struct usb_serial_port *port);
+static void qt2_process_rx_char(struct usb_serial_port *port,
+				unsigned char data);
+
 /* implementation functions, roughly in order of use, are here */
 static int qt2_calc_num_ports(struct usb_serial *serial)
 {
@@ -195,12 +250,13 @@ static int qt2_calc_num_ports(struct usb_serial *serial)
 static int qt2_attach(struct usb_serial *serial)
 {
 	struct usb_serial_port *port;
-	struct quatech2_port *qt2_port;
+	struct quatech2_port *qt2_port;	/* port-specific private data pointer */
+	struct quatech2_dev  *qt2_dev;	/* dev-specific private data pointer */
 	int i;
-	/* stuff for printing endpoint addresses, not needed for
-	 * production */
+	/* stuff for storing endpoint addresses now */
 	struct usb_endpoint_descriptor *endpoint;
 	struct usb_host_interface *iface_desc;
+	struct usb_serial_port *port0;	/* first port structure on device */
 
 	/* check how many endpoints there are on the device, for
 	 * sanity's sake */
@@ -212,12 +268,42 @@ static int qt2_attach(struct usb_serial *serial)
 		return -ENODEV;
 	}
 	iface_desc = serial->interface->cur_altsetting;
+
+	/* Set up per-device private data, storing extra data alongside
+	 * struct usb_serial */
+	qt2_dev = kzalloc(sizeof(*qt2_dev), GFP_KERNEL);
+	if (!qt2_dev) {
+		dbg("%s: kmalloc for quatech2_dev failed!",
+		    __func__);
+		return -ENOMEM;
+	}
+	qt2_dev->open_ports = 0;	/* no ports open */
+	qt2_set_dev_private(serial, qt2_dev);	/* store private data */
+
+	/* Now setup per port private data, which replaces all the things
+	 * that quatech added to standard kernel structures in their driver */
+	for (i = 0; i < serial->num_ports; i++) {
+		port = serial->port[i];
+		qt2_port = kzalloc(sizeof(*qt2_port), GFP_KERNEL);
+		if (!qt2_port) {
+			dbg("%s: kmalloc for quatech2_port (%d) failed!.",
+			    __func__, i);
+			return -ENOMEM;
+		}
+		spin_lock_init(&qt2_port->lock);
+		usb_set_serial_port_data(port, qt2_port);
+	}
+
+	/* gain access to port[0]'s structure because we want to store
+	 * device-level stuff in it */
+	if (serial_paranoia_check(serial, __func__))
+		return -ENODEV;
+	port0 = serial->port[0]; /* get the first port's device structure */
+
 	/* print endpoint addresses so we can check them later
 	 * by hand */
-	for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i)
-	{
+	for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
 		endpoint = &iface_desc->endpoint[i].desc;
-
 		if ((endpoint->bEndpointAddress & 0x80) &&
 			((endpoint->bmAttributes & 3) == 0x02)) {
 			/* we found a bulk in endpoint */
@@ -226,33 +312,13 @@ static int qt2_attach(struct usb_serial *serial)
 		}
 
 		if (((endpoint->bEndpointAddress & 0x80) == 0x00) &&
-				    ((endpoint->bmAttributes & 3) == 0x02))
-		{
+			((endpoint->bmAttributes & 3) == 0x02)) {
 			/* we found a bulk out endpoint */
 			dbg("found bulk out at 0x%x",
 				endpoint->bEndpointAddress);
 		}
 	}	/* end printing endpoint addresses */
 
-	/* Now setup per port private data, which replaces all the things
-	* that quatech added to standard kernel structures in their driver */
-	for (i = 0; i < serial->num_ports; i++) {
-		port = serial->port[i];
-		qt2_port = kzalloc(sizeof(*qt2_port), GFP_KERNEL);
-		if (!qt2_port) {
-			dbg("%s: kmalloc for quatech2_port (%d) failed!.",
-			    __func__, i);
-			return -ENOMEM;
-		}
-		spin_lock_init(&qt2_port->lock);
-		if (i == 0)
-			qt2_port->open_ports = 0; /* no ports */
-		else
-			qt2_port->open_ports = -1; /* unused */
-
-		usb_set_serial_port_data(port, qt2_port);
-
-	}
 	/* switch on power to the hardware */
 	if (qt2_boxpoweron(serial) < 0) {
 		dbg("qt2_boxpoweron() failed");
@@ -274,8 +340,11 @@ startup_error:
 		port = serial->port[i];
 		qt2_port = qt2_get_port_private(port);
 		kfree(qt2_port);
-		usb_set_serial_port_data(port, NULL);
+		qt2_set_port_private(port, NULL);
 	}
+	qt2_dev = qt2_get_dev_private(serial);
+	kfree(qt2_dev);
+	qt2_set_dev_private(serial, NULL);
 
 	dbg("Exit fail %s\n", __func__);
 	return -EIO;
@@ -317,30 +386,40 @@ int qt2_open(struct tty_struct *tty,
 	struct usb_serial_port *port0;	/* first port structure on device */
 	struct quatech2_port *port_extra;	/* extra data for this port */
 	struct quatech2_port *port0_extra;	/* extra data for first port */
+	struct quatech2_dev *dev_extra;		/* extra data for the device */
 	struct qt2_status_data ChannelData;
 	unsigned short default_divisor = QU2BOXSPD9600;
 	unsigned char  default_LCR = SERIAL_8_DATA;
 	int status;
+	int result;
 
 	if (port_paranoia_check(port, __func__))
 		return -ENODEV;
 
-	dbg("%s - port %d\n", __func__, port->number);
+	dbg("%s(): port %d", __func__, port->number);
 
 	serial = port->serial;	/* get the parent device structure */
-	if (serial_paranoia_check(serial, __func__))
+	if (serial_paranoia_check(serial, __func__)) {
+		dbg("usb_serial struct failed sanity check");
 		return -ENODEV;
+	}
+	dev_extra = qt2_get_dev_private(serial);
+	/* get the device private data */
 	port0 = serial->port[0]; /* get the first port's device structure */
-
+	if (port_paranoia_check(port, __func__)) {
+		dbg("port0 usb_serial_port struct failed sanity check");
+		return -ENODEV;
+	}
 	port_extra = qt2_get_port_private(port);
 	port0_extra = qt2_get_port_private(port0);
 
-	if (port_extra == NULL || port0_extra == NULL)
+	if (port_extra == NULL || port0_extra == NULL) {
+		dbg("failed to get private data for port and port0");
 		return -ENODEV;
+	}
 
 	usb_clear_halt(serial->dev, port->write_urb->pipe);
 	usb_clear_halt(serial->dev, port->read_urb->pipe);
-	port0_extra->open_ports++;
 
 	/* FIXME: are these needed?  Does it even do anything useful? */
 	/* get the modem and line status values from the UART */
@@ -374,39 +453,58 @@ int qt2_open(struct tty_struct *tty,
 	dbg("qt2_conf_uart() completed on channel %d",
 		port->number);
 
-	dbg("port number is %d", port->number);
-	dbg("serial number is %d", port->serial->minor);
-
-	/* We need to set up endpoints here. We only
-	 * have one pair of endpoints per device, so in fact
-	 * we only need to set up endpoints on the first time
-	 * round, not subsequent ones.
-	 * When we do a write to a port, we will use the same endpoint
+	/*
+	 * At this point we will need some end points to make further progress.
+	 * Handlily, the correct endpoint addresses have been filled out into
+	 * the usb_serial_port structure for us by the driver core, so we
+	 * already have access to them.
+	 * As there is only one bulk in and one bulk out end-point, these are in
+	 * port[0]'s structure, and the rest are uninitialised. Handily,
+	 * when we do a write to a port, we will use the same endpoint
 	 * regardless of the port, with a 5-byte header added on to
-	 * tell the box which port it should eventually come out of,
-	 * so the same endpoint information needs to be visible to
-	 * write calls regardless of which port is being written.
-	 * To this end we actually keep the relevant endpoints
-	 * in port 0's structure, because that's always there
-	 * and avoids providing our own duplicate members in some
-	 * user data structure for the same purpose.
-	 * URBs will be allocated and freed dynamically as the are
-	 * used, so are not touched here.
+	 * tell the box which port it should eventually come out of, so we only
+	 * need the one set of endpoints.
+	 * Finally we need a bulk in URB to use for background reads from the
+	 * device, which will deal with uplink data from the box to host.
 	 */
-	if (port0_extra->open_ports == 1) {
-		/* this is first port to be opened */
+	dbg("port number is %d", port->number);
+	dbg("serial number is %d", port->serial->minor);
+	dbg("port0 bulk in endpoint is %#.2x", port0->bulk_in_endpointAddress);
+	dbg("port0 bulk out endpoint is %#.2x",
+		port0->bulk_out_endpointAddress);
+
+	if (dev_extra->open_ports == 0) {
+		/* this is first port to be opened, so need some URBs */
+		/* initialise read_urb for bulk in transfers */
+		usb_fill_bulk_urb(port0->read_urb, serial->dev,
+			usb_rcvbulkpipe(serial->dev,
+			port0->bulk_in_endpointAddress),
+			port0->bulk_in_buffer,
+			port0->bulk_in_size,
+			qt2_read_bulk_callback, serial);
+		dbg("port0 bulk in URB intialised");
+
+		/* submit URB, i.e. start reading from device (async) */
+		dev_extra->ReadBulkStopped = false;
+		port_extra->read_urb_busy = true;
+		result = usb_submit_urb(port->read_urb, GFP_KERNEL);
+		if (result) {
+			dev_err(&port->dev,
+				 "%s - Error %d submitting bulk in urb\n",
+				__func__, result);
+			port_extra->read_urb_busy = false;
+		}
 	}
 
-	dbg("Bulkin endpoint is %d", port->bulk_in_endpointAddress);
-	dbg("BulkOut endpoint is %d", port->bulk_out_endpointAddress);
-	dbg("Interrupt endpoint is %d", port->interrupt_in_endpointAddress);
-
 	/* initialize our wait queues */
 	init_waitqueue_head(&port_extra->wait);
 
 	/* remember to store port_extra and port0 back again at end !*/
 	qt2_set_port_private(port, port_extra);
 	qt2_set_port_private(serial->port[0], port0_extra);
+	qt2_set_dev_private(serial, dev_extra);
+
+	dev_extra->open_ports++;	/* one more port opened */
 
 	return 0;
 }
@@ -486,11 +584,22 @@ static inline struct quatech2_port *qt2_get_port_private(struct usb_serial_port
 }
 
 static inline void qt2_set_port_private(struct usb_serial_port *port,
-				       struct quatech2_port *data)
+		struct quatech2_port *data)
 {
 	usb_set_serial_port_data(port, (void *)data);
 }
 
+static inline struct quatech2_dev *qt2_get_dev_private(struct usb_serial
+		*serial)
+{
+	return (struct quatech2_dev *)usb_get_serial_data(serial);
+}
+static inline void qt2_set_dev_private(struct usb_serial *serial,
+		struct quatech2_dev *data)
+{
+	usb_set_serial_data(serial, (void *)data);
+}
+
 static int qt2_openboxchannel(struct usb_serial *serial, __u16
 		Uart_Number, struct qt2_status_data *status)
 {
@@ -534,6 +643,343 @@ static int qt2_conf_uart(struct usb_serial *serial,  unsigned short Uart_Number,
 	return result;
 }
 
+/** @brief Callback for asynchronous submission of URBs on bulk in
+ * endpoints
+ *
+ * Registered in qt2_open_port(), used to deal with incomming data
+ * from the box.
+ */
+static void qt2_read_bulk_callback(struct urb *urb)
+{
+	/* Get the device pointer (struct usb_serial) back out of the URB */
+	struct usb_serial *serial = urb->context;
+	/* get the extra struct for the device */
+	struct quatech2_dev *dev_extra = qt2_get_dev_private(serial);
+	/* Get first port structure from the device */
+	struct usb_serial_port *port0 = serial->port[0];
+	/* Get the currently active port structure from serial struct */
+	struct usb_serial_port *active = dev_extra->current_port;
+	/* get the extra struct for port 0 */
+	struct quatech2_port *port0_extra = qt2_get_port_private(port0);
+	/* and for the currently active port */
+	struct quatech2_port *active_extra = qt2_get_port_private(active);
+	/* When we finally get to doing some tty stuff, we will need this */
+	struct tty_struct *tty_st;
+	unsigned int RxCount;	/* the length of the data to process */
+	unsigned int i;	/* loop counter over the data to process */
+	int result;	/* return value cache variable */
+	bool escapeflag;	/* flag set to true if this loop iteration is
+				 * parsing an escape sequence, rather than
+				 * ordinary data */
+
+
+	dbg("%s(): callback running", __func__);
+
+	if (urb->status) {
+		/* read didn't go well */
+		dev_extra->ReadBulkStopped = true;
+		dbg("%s(): nonzero write bulk status received: %d",
+			__func__, urb->status);
+		return;
+	}
+
+	/* inline port_sofrint() here */
+	if (port_paranoia_check(port0, __func__) != 0) {
+		dbg("%s - port_paranoia_check on port0 failed, exiting\n",
+__func__);
+		return;
+	}
+	if (port_paranoia_check(active, __func__) != 0) {
+		dbg("%s - port_paranoia_check on current_port "
+			"failed, exiting", __func__);
+		return;
+	}
+
+/* This single callback function has to do for all the ports on
+ * the device. Data being read up the USB can contain certain
+ * escape sequences which are used to communicate out-of-band
+ * information from the serial port in-band over the USB.
+ * These escapes include sending modem and flow control line
+ * status, and switching the port. The concept of a "Current Port"
+ * is used, which is where data is going until a port change
+ * escape seqence is received. This Current Port is kept between
+ * callbacks so that when this function enters we know which the
+ * currently active port is and can get to work right away without
+ * the box having to send repeat escape sequences (anyway, how
+ * would it know to do so?).
+ */
+
+	if (active_extra->close_pending == true) {
+		/* We are closing , stop reading */
+		dbg("%s - (active->close_pending == true", __func__);
+		if (dev_extra->open_ports <= 0) {
+			/* If this is the only port left open - stop the
+			 * bulk read */
+			dev_extra->ReadBulkStopped = true;
+			dbg("%s - (ReadBulkStopped == true;", __func__);
+			return;
+		}
+	}
+
+	/*
+	 * RxHolding is asserted by throttle, if we assert it, we're not
+	 * receiving any more characters and let the box handle the flow
+	 * control
+	 */
+	if ((port0_extra->RxHolding == true) &&
+		    (serial->dev->descriptor.idProduct == QUATECH_SSU2_100)) {
+		/* single port device, input is already stopped, so we don't
+		 * need any more input data */
+		dev_extra->ReadBulkStopped = true;
+			return;
+	}
+	/* finally, we are in a situation where we might consider the data
+	 * that is contained within the URB, and what to do about it.
+	 * This is likely to involved communicating up to the TTY layer, so
+	 * we will need to get hold of the tty for the port we are currently
+	 * dealing with */
+
+	/* active is a usb_serial_port. It has a member port which is a
+	 * tty_port. From this we get a tty_struct pointer which is what we
+	 * actually wanted, and keep it on tty_st */
+	tty_st = tty_port_tty_get(&active->port);
+	if (!tty_st) {
+		dbg("%s - bad tty pointer - exiting", __func__);
+		return;
+	}
+	dbg("%s(): active port %d, tty_st =0x%p\n", __func__, active->number,
+		tty_st);
+	RxCount = urb->actual_length;	/* grab length of data handy */
+
+	if (RxCount) {
+		/* skip all this if no data to process */
+		for (i = 0; i < RxCount ; ++i) {
+			/* Look ahead code here -works on several bytes at onc*/
+			if ((i <= (RxCount - 3)) && (THISCHAR == 0x1b)
+				&& (NEXTCHAR == 0x1b)) {
+				/* we are in an escape sequence, type
+				 * determined by the 3rd char */
+				escapeflag = false;
+				switch (THIRDCHAR) {
+				case 0x00:
+					/* Line status change 4th byte must
+					 * follow */
+					if (i > (RxCount - 4)) {
+						dbg("Illegal escape sequences "
+						"in received data");
+						break;
+					}
+					qt2_process_line_status(active,
+						FOURTHCHAR);
+					i += 3;
+					escapeflag = true;
+					break;
+				case 0x01:
+					/* Modem status status change 4th byte
+					 * must follow */
+					if (i > (RxCount - 4)) {
+						dbg("Illegal escape sequences "
+						"in received data");
+						break;
+					}
+					qt2_process_modem_status(active,
+						FOURTHCHAR);
+					i += 3;
+					escapeflag = true;
+					break;
+				case 0x02:
+					/* xmit hold empty 4th byte
+					 * must follow */
+					if (i > (RxCount - 4)) {
+						dbg("Illegal escape sequences "
+						"in received data");
+						break;
+					}
+					qt2_process_xmit_empty(active,
+						FOURTHCHAR,
+							FIFTHCHAR);
+					i += 4;
+					escapeflag = true;
+					break;
+				case 0x03:
+					/* Port number change 4th byte
+					 * must follow */
+					if (i > (RxCount - 4)) {
+						dbg("Illegal escape sequences "
+						"in received data");
+						break;
+					}
+					/* Port change. If port open push
+					 * current data up to tty layer */
+					if (dev_extra->open_ports > 0)
+						tty_flip_buffer_push(tty_st);
+
+					dbg("Port Change: new port = %d",
+						FOURTHCHAR);
+					qt2_process_port_change(active,
+						FOURTHCHAR);
+					i += 3;
+					escapeflag = true;
+					/* having changed port, the pointers for
+					 * the currently active port are all out
+					 * of date and need updating */
+					active = dev_extra->current_port;
+					active_extra =
+						qt2_get_port_private(active);
+					tty_st = tty_port_tty_get(
+						&active->port);
+					break;
+				case 0x04:
+					/* Recv flush 3rd byte must
+					 * follow */
+					if (i > (RxCount - 3)) {
+						dbg("Illegal escape sequences "
+							"in received data");
+						break;
+					}
+					qt2_process_rcv_flush(active);
+					i += 2;
+					escapeflag = true;
+					break;
+				case 0x05:
+					/* xmit flush 3rd byte must follow */
+					if (i > (RxCount - 3)) {
+						dbg("Illegal escape sequences "
+						"in received data");
+						break;
+					}
+					qt2_process_xmit_flush(active);
+					i += 2;
+					escapeflag = true;
+					break;
+				case 0xff:
+					dbg("No status sequence");
+					qt2_process_rx_char(active, THISCHAR);
+					qt2_process_rx_char(active, NEXTCHAR);
+					i += 2;
+					break;
+				default:
+					qt2_process_rx_char(active, THISCHAR);
+					i += 1;
+					break;
+				} /*end switch*/
+				if (escapeflag == true)
+					continue;
+				/* if we did an escape char, we don't need
+				 * to mess around pushing data through the
+				 * tty layer, and can go round again */
+			} /*endif*/
+			if (tty_st && urb->actual_length) {
+				tty_buffer_request_room(tty_st, 1);
+				tty_insert_flip_string(tty_st,
+					&((unsigned char *)(urb->transfer_buffer)
+						)[i],
+					1);
+			}
+		} /*endfor*/
+		tty_flip_buffer_push(tty_st);
+	} /*endif*/
+
+	/* at this point we have complete dealing with the data for this
+	 * callback. All we have to do now is to start the async read process
+	 * back off again. */
+
+	usb_fill_bulk_urb(port0->read_urb, serial->dev,
+		usb_rcvbulkpipe(serial->dev, port0->bulk_in_endpointAddress),
+		port0->bulk_in_buffer, port0->bulk_in_size,
+		qt2_read_bulk_callback, serial);
+	result = usb_submit_urb(port0->read_urb, GFP_ATOMIC);
+	if (result) {
+		dbg("%s(): failed resubmitting read urb, error %d",
+			__func__, result);
+	} else {
+		if (tty_st && RxCount) {
+			/* if some inbound data was processed, then
+			 * we need to push that through the tty layer
+			 */
+			tty_flip_buffer_push(tty_st);
+			tty_schedule_flip(tty_st);
+		}
+	}
+
+	/* cribbed from serqt_usb2 driver, but not sure which work needs
+	 * scheduling - port0 or currently active port? */
+	/* schedule_work(&port->work); */
+
+	return;
+}
+static void qt2_process_line_status(struct usb_serial_port *port,
+	unsigned char LineStatus)
+{
+	/* obtain the private structure for the port */
+	struct quatech2_port *port_extra = qt2_get_port_private(port);
+	port_extra->shadowLSR = LineStatus & (SERIAL_LSR_OE | SERIAL_LSR_PE |
+		SERIAL_LSR_FE | SERIAL_LSR_BI);
+}
+static void qt2_process_modem_status(struct usb_serial_port *port,
+	unsigned char ModemStatus)
+{
+	/* obtain the private structure for the port */
+	struct quatech2_port *port_extra = qt2_get_port_private(port);
+	port_extra->shadowMSR = ModemStatus;
+	/* ?? */
+	wake_up_interruptible(&port_extra->wait);
+}
+
+static void qt2_process_xmit_empty(struct usb_serial_port *port,
+	unsigned char fourth_char, unsigned char fifth_char)
+{
+	int byte_count;
+	/* obtain the private structure for the port */
+	struct quatech2_port *port_extra = qt2_get_port_private(port);
+
+	byte_count = (int)(fifth_char * 16);
+	byte_count +=  (int)fourth_char;
+	port_extra->xmit_pending_bytes -= (int)byte_count;
+	port_extra->xmit_fifo_room_bytes = FIFO_DEPTH;
+}
+
+static void qt2_process_port_change(struct usb_serial_port *port,
+	unsigned char New_Current_Port)
+{
+	/* obtain the parent usb serial device structure */
+	struct usb_serial *serial = port->serial;
+	/* obtain the private structure for the device */
+	struct quatech2_dev *dev_extra = qt2_get_dev_private(serial);
+	dev_extra->current_port = serial->port[New_Current_Port];
+	/* what should I do with this? commented out in upstream
+	 * driver */
+	/*schedule_work(&port->work);*/
+}
+
+static void qt2_process_rcv_flush(struct usb_serial_port *port)
+{
+	/* obtain the private structure for the port */
+	struct quatech2_port *port_extra = qt2_get_port_private(port);
+	port_extra->rcv_flush = true;
+}
+static void qt2_process_xmit_flush(struct usb_serial_port *port)
+{
+	/* obtain the private structure for the port */
+	struct quatech2_port *port_extra = qt2_get_port_private(port);
+	port_extra->xmit_flush = true;
+}
+
+static void qt2_process_rx_char(struct usb_serial_port *port,
+	unsigned char data)
+{
+	/* get the tty_struct for this port */
+	struct tty_struct *tty = tty_port_tty_get(&(port->port));
+	/* get the URB with the data in to push */
+	struct urb *urb = port->serial->port[0]->read_urb;
+
+	if (tty && urb->actual_length) {
+		tty_buffer_request_room(tty, 1);
+		tty_insert_flip_string(tty, &data, 1);
+		/* should this be commented out here? */
+		/*tty_flip_buffer_push(tty);*/
+	}
+}
 /*
  * last things in file: stuff to register this driver into the generic
  * USB serial framework.