[PATCH] isdn4linux: Siemens Gigaset drivers - direct USB connection

And: Tilman Schmidt <tilman@imap.cc>

This patch adds the main source file of the connection-specific module
"bas_gigaset", the hardware driver for Gigaset base stations connected
directly to the computer via USB.  It contains the code for handling
probe/disconnect, AT command/response transmission, and call setup and
termination.

Signed-off-by: Hansjoerg Lipp <hjlipp@web.de>
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Cc: Karsten Keil <kkeil@suse.de>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2365 insertions, 0 deletions

diff --git a/drivers/isdn/gigaset/bas-gigaset.c b/drivers/isdn/gigaset/bas-gigaset.c
new file mode 100644
index 000000000000..31f0f07832bc
--- /dev/null
+++ b/drivers/isdn/gigaset/bas-gigaset.c
@@ -0,0 +1,2365 @@
+/*
+ * USB driver for Gigaset 307x base via direct USB connection.
+ *
+ * Copyright (c) 2001 by Hansjoerg Lipp <hjlipp@web.de>,
+ *                       Tilman Schmidt <tilman@imap.cc>,
+ *                       Stefan Eilers <Eilers.Stefan@epost.de>.
+ *
+ * Based on usb-gigaset.c.
+ *
+ * =====================================================================
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License as
+ *	published by the Free Software Foundation; either version 2 of
+ *	the License, or (at your option) any later version.
+ * =====================================================================
+ * ToDo: ...
+ * =====================================================================
+ * Version: $Id: bas-gigaset.c,v 1.52.4.19 2006/02/04 18:28:16 hjlipp Exp $
+ * =====================================================================
+ */
+
+#include "gigaset.h"
+
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/timer.h>
+#include <linux/usb.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+
+/* Version Information */
+#define DRIVER_AUTHOR "Tilman Schmidt <tilman@imap.cc>, Hansjoerg Lipp <hjlipp@web.de>, Stefan Eilers <Eilers.Stefan@epost.de>"
+#define DRIVER_DESC "USB Driver for Gigaset 307x"
+
+
+/* Module parameters */
+
+static int startmode = SM_ISDN;
+static int cidmode = 1;
+
+module_param(startmode, int, S_IRUGO);
+module_param(cidmode, int, S_IRUGO);
+MODULE_PARM_DESC(startmode, "start in isdn4linux mode");
+MODULE_PARM_DESC(cidmode, "Call-ID mode");
+
+#define GIGASET_MINORS     1
+#define GIGASET_MINOR      16
+#define GIGASET_MODULENAME "bas_gigaset"
+#define GIGASET_DEVFSNAME  "gig/bas/"
+#define GIGASET_DEVNAME    "ttyGB"
+
+#define IF_WRITEBUF 256 //FIXME
+
+/* Values for the Gigaset 307x */
+#define USB_GIGA_VENDOR_ID      0x0681
+#define USB_GIGA_PRODUCT_ID     0x0001
+#define USB_4175_PRODUCT_ID     0x0002
+#define USB_SX303_PRODUCT_ID    0x0021
+#define USB_SX353_PRODUCT_ID    0x0022
+
+/* table of devices that work with this driver */
+static struct usb_device_id gigaset_table [] = {
+	{ USB_DEVICE(USB_GIGA_VENDOR_ID, USB_GIGA_PRODUCT_ID) },
+	{ USB_DEVICE(USB_GIGA_VENDOR_ID, USB_4175_PRODUCT_ID) },
+	{ USB_DEVICE(USB_GIGA_VENDOR_ID, USB_SX303_PRODUCT_ID) },
+	{ USB_DEVICE(USB_GIGA_VENDOR_ID, USB_SX353_PRODUCT_ID) },
+	{ } /* Terminating entry */
+};
+
+MODULE_DEVICE_TABLE(usb, gigaset_table);
+
+/* Get a minor range for your devices from the usb maintainer */
+#define USB_SKEL_MINOR_BASE	200
+
+/*======================= local function prototypes =============================*/
+
+/* This function is called if a new device is connected to the USB port. It
+ * checks whether this new device belongs to this driver.
+ */
+static int gigaset_probe(struct usb_interface *interface,
+			 const struct usb_device_id *id);
+
+/* Function will be called if the device is unplugged */
+static void gigaset_disconnect(struct usb_interface *interface);
+
+
+/*==============================================================================*/
+
+struct bas_cardstate {
+	struct usb_device       *udev;		/* USB device pointer */
+	struct usb_interface    *interface;	/* interface for this device */
+	unsigned char		minor;		/* starting minor number */
+
+	struct urb              *urb_ctrl;	/* control pipe default URB */
+	struct usb_ctrlrequest	dr_ctrl;
+	struct timer_list	timer_ctrl;	/* control request timeout */
+
+	struct timer_list	timer_atrdy;	/* AT command ready timeout */
+	struct urb              *urb_cmd_out;	/* for sending AT commands */
+	struct usb_ctrlrequest	dr_cmd_out;
+	int			retry_cmd_out;
+
+	struct urb              *urb_cmd_in;	/* for receiving AT replies */
+	struct usb_ctrlrequest	dr_cmd_in;
+	struct timer_list	timer_cmd_in;	/* receive request timeout */
+	unsigned char           *rcvbuf;	/* AT reply receive buffer */
+
+	struct urb              *urb_int_in;	/* URB for interrupt pipe */
+	unsigned char		int_in_buf[3];
+
+	spinlock_t		lock;		/* locks all following */
+	atomic_t		basstate;	/* bitmap (BS_*) */
+	int			pending;	/* uncompleted base request */
+	int			rcvbuf_size;	/* size of AT receive buffer */
+						/* 0: no receive in progress */
+	int			retry_cmd_in;	/* receive req retry count */
+};
+
+/* status of direct USB connection to 307x base (bits in basstate) */
+#define BS_ATOPEN	0x001
+#define BS_B1OPEN	0x002
+#define BS_B2OPEN	0x004
+#define BS_ATREADY	0x008
+#define BS_INIT		0x010
+#define BS_ATTIMER	0x020
+
+
+static struct gigaset_driver *driver = NULL;
+static struct cardstate *cardstate = NULL;
+
+/* usb specific object needed to register this driver with the usb subsystem */
+static struct usb_driver gigaset_usb_driver = {
+	.name =         GIGASET_MODULENAME,
+	.probe =        gigaset_probe,
+	.disconnect =   gigaset_disconnect,
+	.id_table =     gigaset_table,
+};
+
+/* get message text for USB status code
+ */
+static char *get_usb_statmsg(int status)
+{
+	static char unkmsg[28];
+
+	switch (status) {
+	case 0:
+		return "success";
+	case -ENOENT:
+		return "canceled";
+	case -ECONNRESET:
+		return "canceled (async)";
+	case -EINPROGRESS:
+		return "pending";
+	case -EPROTO:
+		return "bit stuffing or unknown USB error";
+	case -EILSEQ:
+		return "Illegal byte sequence (CRC mismatch)";
+	case -EPIPE:
+		return "babble detect or endpoint stalled";
+	case -ENOSR:
+		return "buffer error";
+	case -ETIMEDOUT:
+		return "timed out";
+	case -ENODEV:
+		return "device not present";
+	case -EREMOTEIO:
+		return "short packet detected";
+	case -EXDEV:
+		return "partial isochronous transfer";
+	case -EINVAL:
+		return "invalid argument";
+	case -ENXIO:
+		return "URB already queued";
+	case -EAGAIN:
+		return "isochronous start frame too early or too much scheduled";
+	case -EFBIG:
+		return "too many isochronous frames requested";
+	case -EMSGSIZE:
+		return "endpoint message size zero";
+	case -ESHUTDOWN:
+		return "endpoint shutdown";
+	case -EBUSY:
+		return "another request pending";
+	default:
+		snprintf(unkmsg, sizeof(unkmsg), "unknown error %d", status);
+		return unkmsg;
+	}
+}
+
+/* usb_pipetype_str
+ * retrieve string representation of USB pipe type
+ */
+static inline char *usb_pipetype_str(int pipe)
+{
+	if (usb_pipeisoc(pipe))
+		return "Isoc";
+	if (usb_pipeint(pipe))
+		return "Int";
+	if (usb_pipecontrol(pipe))
+		return "Ctrl";
+	if (usb_pipebulk(pipe))
+		return "Bulk";
+	return "?";
+}
+
+/* dump_urb
+ * write content of URB to syslog for debugging
+ */
+static inline void dump_urb(enum debuglevel level, const char *tag,
+                            struct urb *urb)
+{
+#ifdef CONFIG_GIGASET_DEBUG
+	int i;
+	IFNULLRET(tag);
+	dbg(level, "%s urb(0x%08lx)->{", tag, (unsigned long) urb);
+	if (urb) {
+		dbg(level,
+		    "  dev=0x%08lx, pipe=%s:EP%d/DV%d:%s, "
+		    "status=%d, hcpriv=0x%08lx, transfer_flags=0x%x,",
+		    (unsigned long) urb->dev,
+		    usb_pipetype_str(urb->pipe),
+		    usb_pipeendpoint(urb->pipe), usb_pipedevice(urb->pipe),
+		    usb_pipein(urb->pipe) ? "in" : "out",
+		    urb->status, (unsigned long) urb->hcpriv,
+		    urb->transfer_flags);
+		dbg(level,
+		    "  transfer_buffer=0x%08lx[%d], actual_length=%d, "
+		    "bandwidth=%d, setup_packet=0x%08lx,",
+		    (unsigned long) urb->transfer_buffer,
+		    urb->transfer_buffer_length, urb->actual_length,
+		    urb->bandwidth, (unsigned long) urb->setup_packet);
+		dbg(level,
+		    "  start_frame=%d, number_of_packets=%d, interval=%d, "
+		    "error_count=%d,",
+		    urb->start_frame, urb->number_of_packets, urb->interval,
+		    urb->error_count);
+		dbg(level,
+		    "  context=0x%08lx, complete=0x%08lx, iso_frame_desc[]={",
+		    (unsigned long) urb->context,
+		    (unsigned long) urb->complete);
+		for (i = 0; i < urb->number_of_packets; i++) {
+			struct usb_iso_packet_descriptor *pifd = &urb->iso_frame_desc[i];
+			dbg(level,
+			    "    {offset=%u, length=%u, actual_length=%u, "
+			    "status=%u}",
+			    pifd->offset, pifd->length, pifd->actual_length,
+			    pifd->status);
+		}
+	}
+	dbg(level, "}}");
+#endif
+}
+
+/* read/set modem control bits etc. (m10x only) */
+static int gigaset_set_modem_ctrl(struct cardstate *cs, unsigned old_state,
+                                  unsigned new_state)
+{
+	return -EINVAL;
+}
+
+static int gigaset_baud_rate(struct cardstate *cs, unsigned cflag)
+{
+	return -EINVAL;
+}
+
+static int gigaset_set_line_ctrl(struct cardstate *cs, unsigned cflag)
+{
+	return -EINVAL;
+}
+
+/* error_hangup
+ * hang up any existing connection because of an unrecoverable error
+ * This function may be called from any context and takes care of scheduling
+ * the necessary actions for execution outside of interrupt context.
+ * argument:
+ *	B channel control structure
+ */
+static inline void error_hangup(struct bc_state *bcs)
+{
+	struct cardstate *cs = bcs->cs;
+
+	dbg(DEBUG_ANY,
+	    "%s: scheduling HUP for channel %d", __func__, bcs->channel);
+
+	if (!gigaset_add_event(cs, &bcs->at_state, EV_HUP, NULL, 0, NULL)) {
+		//FIXME what should we do?
+		return;
+	}
+
+	gigaset_schedule_event(cs);
+}
+
+/* error_reset
+ * reset Gigaset device because of an unrecoverable error
+ * This function may be called from any context and takes care of scheduling
+ * the necessary actions for execution outside of interrupt context.
+ * argument:
+ *	controller state structure
+ */
+static inline void error_reset(struct cardstate *cs)
+{
+	//FIXME try to recover without bothering the user
+	err("unrecoverable error - please disconnect the Gigaset base to reset");
+}
+
+/* check_pending
+ * check for completion of pending control request
+ * parameter:
+ *	urb	USB request block of completed request
+ *		urb->context = hardware specific controller state structure
+ */
+static void check_pending(struct bas_cardstate *ucs)
+{
+	unsigned long flags;
+
+	IFNULLRET(ucs);
+	IFNULLRET(cardstate);
+
+	spin_lock_irqsave(&ucs->lock, flags);
+	switch (ucs->pending) {
+	case 0:
+		break;
+	case HD_OPEN_ATCHANNEL:
+		if (atomic_read(&ucs->basstate) & BS_ATOPEN)
+			ucs->pending = 0;
+		break;
+	case HD_OPEN_B1CHANNEL:
+		if (atomic_read(&ucs->basstate) & BS_B1OPEN)
+			ucs->pending = 0;
+		break;
+	case HD_OPEN_B2CHANNEL:
+		if (atomic_read(&ucs->basstate) & BS_B2OPEN)
+			ucs->pending = 0;
+		break;
+	case HD_CLOSE_ATCHANNEL:
+		if (!(atomic_read(&ucs->basstate) & BS_ATOPEN))
+			ucs->pending = 0;
+		//wake_up_interruptible(cs->initwait);
+		//FIXME need own wait queue?
+		break;
+	case HD_CLOSE_B1CHANNEL:
+		if (!(atomic_read(&ucs->basstate) & BS_B1OPEN))
+			ucs->pending = 0;
+		break;
+	case HD_CLOSE_B2CHANNEL:
+		if (!(atomic_read(&ucs->basstate) & BS_B2OPEN))
+			ucs->pending = 0;
+		break;
+	case HD_DEVICE_INIT_ACK:		/* no reply expected */
+		ucs->pending = 0;
+		break;
+	/* HD_READ_ATMESSAGE, HD_WRITE_ATMESSAGE, HD_RESET_INTERRUPTPIPE
+	 * are handled separately and should never end up here
+	 */
+	default:
+		warn("unknown pending request 0x%02x cleared", ucs->pending);
+		ucs->pending = 0;
+	}
+
+	if (!ucs->pending)
+		del_timer(&ucs->timer_ctrl);
+
+	spin_unlock_irqrestore(&ucs->lock, flags);
+}
+
+/* cmd_in_timeout
+ * timeout routine for command input request
+ * argument:
+ *	controller state structure
+ */
+static void cmd_in_timeout(unsigned long data)
+{
+	struct cardstate *cs = (struct cardstate *) data;
+	struct bas_cardstate *ucs;
+	unsigned long flags;
+
+	IFNULLRET(cs);
+	ucs = cs->hw.bas;
+	IFNULLRET(ucs);
+
+	spin_lock_irqsave(&cs->lock, flags);
+	if (!atomic_read(&cs->connected)) {
+		dbg(DEBUG_USBREQ, "%s: disconnected", __func__);
+		spin_unlock_irqrestore(&cs->lock, flags);
+		return;
+	}
+	if (!ucs->rcvbuf_size) {
+		dbg(DEBUG_USBREQ, "%s: no receive in progress", __func__);
+		spin_unlock_irqrestore(&cs->lock, flags);
+		return;
+	}
+	spin_unlock_irqrestore(&cs->lock, flags);
+
+	err("timeout reading AT response");
+	error_reset(cs);	//FIXME retry?
+}
+
+
+static void read_ctrl_callback(struct urb *urb, struct pt_regs *regs);
+
+/* atread_submit
+ * submit an HD_READ_ATMESSAGE command URB
+ * parameters:
+ *	cs	controller state structure
+ *	timeout	timeout in 1/10 sec., 0: none
+ * return value:
+ *	0 on success
+ *	-EINVAL if a NULL pointer is encountered somewhere
+ *	-EBUSY if another request is pending
+ *	any URB submission error code
+ */
+static int atread_submit(struct cardstate *cs, int timeout)
+{
+	struct bas_cardstate *ucs;
+	int ret;
+
+	IFNULLRETVAL(cs, -EINVAL);
+	ucs = cs->hw.bas;
+	IFNULLRETVAL(ucs, -EINVAL);
+	IFNULLRETVAL(ucs->urb_cmd_in, -EINVAL);
+
+	dbg(DEBUG_USBREQ, "-------> HD_READ_ATMESSAGE (%d)", ucs->rcvbuf_size);
+
+	if (ucs->urb_cmd_in->status == -EINPROGRESS) {
+		err("could not submit HD_READ_ATMESSAGE: URB busy");
+		return -EBUSY;
+	}
+
+	ucs->dr_cmd_in.bRequestType = IN_VENDOR_REQ;
+	ucs->dr_cmd_in.bRequest = HD_READ_ATMESSAGE;
+	ucs->dr_cmd_in.wValue = 0;
+	ucs->dr_cmd_in.wIndex = 0;
+	ucs->dr_cmd_in.wLength = cpu_to_le16(ucs->rcvbuf_size);
+	usb_fill_control_urb(ucs->urb_cmd_in, ucs->udev,
+	                     usb_rcvctrlpipe(ucs->udev, 0),
+	                     (unsigned char*) & ucs->dr_cmd_in,
+	                     ucs->rcvbuf, ucs->rcvbuf_size,
+	                     read_ctrl_callback, cs->inbuf);
+
+	if ((ret = usb_submit_urb(ucs->urb_cmd_in, SLAB_ATOMIC)) != 0) {
+		err("could not submit HD_READ_ATMESSAGE: %s",
+		    get_usb_statmsg(ret));
+		return ret;
+	}
+
+	if (timeout > 0) {
+		dbg(DEBUG_USBREQ, "setting timeout of %d/10 secs", timeout);
+		ucs->timer_cmd_in.expires = jiffies + timeout * HZ / 10;
+		ucs->timer_cmd_in.data = (unsigned long) cs;
+		ucs->timer_cmd_in.function = cmd_in_timeout;
+		add_timer(&ucs->timer_cmd_in);
+	}
+	return 0;
+}
+
+static void stopurbs(struct bas_bc_state *);
+static int start_cbsend(struct cardstate *);
+
+/* set/clear bits in base connection state
+ */
+inline static void update_basstate(struct bas_cardstate *ucs,
+				   int set, int clear)
+{
+	unsigned long flags;
+	int state;
+
+	spin_lock_irqsave(&ucs->lock, flags);
+	state = atomic_read(&ucs->basstate);
+	state &= ~clear;
+	state |= set;
+	atomic_set(&ucs->basstate, state);
+	spin_unlock_irqrestore(&ucs->lock, flags);
+}
+
+
+/* read_int_callback
+ * USB completion handler for interrupt pipe input
+ * called by the USB subsystem in interrupt context
+ * parameter:
+ *	urb	USB request block
+ *		urb->context = controller state structure
+ */
+static void read_int_callback(struct urb *urb, struct pt_regs *regs)
+{
+	struct cardstate *cs;
+	struct bas_cardstate *ucs;
+	struct bc_state *bcs;
+	unsigned long flags;
+	int status;
+	unsigned l;
+	int channel;
+
+	IFNULLRET(urb);
+	cs = (struct cardstate *) urb->context;
+	IFNULLRET(cs);
+	ucs = cs->hw.bas;
+	IFNULLRET(ucs);
+
+	if (unlikely(!atomic_read(&cs->connected))) {
+		warn("%s: disconnected", __func__);
+		return;
+	}
+
+	switch (urb->status) {
+	case 0:			/* success */
+		break;
+	case -ENOENT:			/* canceled */
+	case -ECONNRESET:		/* canceled (async) */
+	case -EINPROGRESS:		/* pending */
+		/* ignore silently */
+		dbg(DEBUG_USBREQ,
+		    "%s: %s", __func__, get_usb_statmsg(urb->status));
+		return;
+	default:		/* severe trouble */
+		warn("interrupt read: %s", get_usb_statmsg(urb->status));
+		//FIXME corrective action? resubmission always ok?
+		goto resubmit;
+	}
+
+	l = (unsigned) ucs->int_in_buf[1] +
+	    (((unsigned) ucs->int_in_buf[2]) << 8);
+
+	dbg(DEBUG_USBREQ,
+	    "<-------%d: 0x%02x (%u [0x%02x 0x%02x])", urb->actual_length,
+	    (int)ucs->int_in_buf[0], l,
+	    (int)ucs->int_in_buf[1], (int)ucs->int_in_buf[2]);
+
+	channel = 0;
+
+	switch (ucs->int_in_buf[0]) {
+	case HD_DEVICE_INIT_OK:
+		update_basstate(ucs, BS_INIT, 0);
+		break;
+
+	case HD_READY_SEND_ATDATA:
+		del_timer(&ucs->timer_atrdy);
+		update_basstate(ucs, BS_ATREADY, BS_ATTIMER);
+		start_cbsend(cs);
+		break;
+
+	case HD_OPEN_B2CHANNEL_ACK:
+		++channel;
+	case HD_OPEN_B1CHANNEL_ACK:
+		bcs = cs->bcs + channel;
+		update_basstate(ucs, BS_B1OPEN << channel, 0);
+		gigaset_bchannel_up(bcs);
+		break;
+
+	case HD_OPEN_ATCHANNEL_ACK:
+		update_basstate(ucs, BS_ATOPEN, 0);
+		start_cbsend(cs);
+		break;
+
+	case HD_CLOSE_B2CHANNEL_ACK:
+		++channel;
+	case HD_CLOSE_B1CHANNEL_ACK:
+		bcs = cs->bcs + channel;
+		update_basstate(ucs, 0, BS_B1OPEN << channel);
+		stopurbs(bcs->hw.bas);
+		gigaset_bchannel_down(bcs);
+		break;
+
+	case HD_CLOSE_ATCHANNEL_ACK:
+		update_basstate(ucs, 0, BS_ATOPEN);
+		break;
+
+	case HD_B2_FLOW_CONTROL:
+		++channel;
+	case HD_B1_FLOW_CONTROL:
+		bcs = cs->bcs + channel;
+		atomic_add((l - BAS_NORMFRAME) * BAS_CORRFRAMES,
+		           &bcs->hw.bas->corrbytes);
+		dbg(DEBUG_ISO,
+		    "Flow control (channel %d, sub %d): 0x%02x => %d",
+		    channel, bcs->hw.bas->numsub, l,
+		    atomic_read(&bcs->hw.bas->corrbytes));
+		break;
+
+	case HD_RECEIVEATDATA_ACK:	/* AT response ready to be received */
+		if (!l) {
+			warn("HD_RECEIVEATDATA_ACK with length 0 ignored");
+			break;
+		}
+		spin_lock_irqsave(&cs->lock, flags);
+		if (ucs->rcvbuf_size) {
+			spin_unlock_irqrestore(&cs->lock, flags);
+			err("receive AT data overrun, %d bytes lost", l);
+			error_reset(cs);	//FIXME reschedule
+			break;
+		}
+		if ((ucs->rcvbuf = kmalloc(l, GFP_ATOMIC)) == NULL) {
+			spin_unlock_irqrestore(&cs->lock, flags);
+			err("%s: out of memory, %d bytes lost", __func__, l);
+			error_reset(cs);	//FIXME reschedule
+			break;
+		}
+		ucs->rcvbuf_size = l;
+		ucs->retry_cmd_in = 0;
+		if ((status = atread_submit(cs, BAS_TIMEOUT)) < 0) {
+			kfree(ucs->rcvbuf);
+			ucs->rcvbuf = NULL;
+			ucs->rcvbuf_size = 0;
+			error_reset(cs);	//FIXME reschedule
+		}
+		spin_unlock_irqrestore(&cs->lock, flags);
+		break;
+
+	case HD_RESET_INTERRUPT_PIPE_ACK:
+		dbg(DEBUG_USBREQ, "HD_RESET_INTERRUPT_PIPE_ACK");
+		break;
+
+	case HD_SUSPEND_END:
+		dbg(DEBUG_USBREQ, "HD_SUSPEND_END");
+		break;
+
+	default:
+		warn("unknown Gigaset signal 0x%02x (%u) ignored",
+		     (int) ucs->int_in_buf[0], l);
+	}
+
+	check_pending(ucs);
+
+resubmit:
+	status = usb_submit_urb(urb, SLAB_ATOMIC);
+	if (unlikely(status)) {
+		err("could not resubmit interrupt URB: %s",
+		    get_usb_statmsg(status));
+		error_reset(cs);
+	}
+}
+
+/* read_ctrl_callback
+ * USB completion handler for control pipe input
+ * called by the USB subsystem in interrupt context
+ * parameter:
+ *	urb	USB request block
+ *		urb->context = inbuf structure for controller state
+ */
+static void read_ctrl_callback(struct urb *urb, struct pt_regs *regs)
+{
+	struct cardstate *cs;
+	struct bas_cardstate *ucs;
+	unsigned numbytes;
+	unsigned long flags;
+	struct inbuf_t *inbuf;
+	int have_data = 0;
+
+	IFNULLRET(urb);
+	inbuf = (struct inbuf_t *) urb->context;
+	IFNULLRET(inbuf);
+	cs = inbuf->cs;
+	IFNULLRET(cs);
+	ucs = cs->hw.bas;
+	IFNULLRET(ucs);
+
+	spin_lock_irqsave(&cs->lock, flags);
+	if (!atomic_read(&cs->connected)) {
+		warn("%s: disconnected", __func__);
+		spin_unlock_irqrestore(&cs->lock, flags);
+		return;
+	}
+
+	if (!ucs->rcvbuf_size) {
+		warn("%s: no receive in progress", __func__);
+		spin_unlock_irqrestore(&cs->lock, flags);
+		return;
+	}
+
+	del_timer(&ucs->timer_cmd_in);
+
+	switch (urb->status) {
+	case 0:				/* normal completion */
+		numbytes = urb->actual_length;
+		if (unlikely(numbytes == 0)) {
+			warn("control read: empty block received");
+			goto retry;
+		}
+		if (unlikely(numbytes != ucs->rcvbuf_size)) {
+			warn("control read: received %d chars, expected %d",
+			     numbytes, ucs->rcvbuf_size);
+			if (numbytes > ucs->rcvbuf_size)
+				numbytes = ucs->rcvbuf_size;
+		}
+
+		/* copy received bytes to inbuf */
+		have_data = gigaset_fill_inbuf(inbuf, ucs->rcvbuf, numbytes);
+
+		if (unlikely(numbytes < ucs->rcvbuf_size)) {
+			/* incomplete - resubmit for remaining bytes */
+			ucs->rcvbuf_size -= numbytes;
+			ucs->retry_cmd_in = 0;
+			goto retry;
+		}
+		break;
+
+	case -ENOENT:			/* canceled */
+	case -ECONNRESET:		/* canceled (async) */
+	case -EINPROGRESS:		/* pending */
+		/* no action necessary */
+		dbg(DEBUG_USBREQ,
+		    "%s: %s", __func__, get_usb_statmsg(urb->status));
+		break;
+
+	default:			/* severe trouble */
+		warn("control read: %s", get_usb_statmsg(urb->status));
+	retry:
+		if (ucs->retry_cmd_in++ < BAS_RETRY) {
+			notice("control read: retry %d", ucs->retry_cmd_in);
+			if (atread_submit(cs, BAS_TIMEOUT) >= 0) {
+				/* resubmitted - bypass regular exit block */
+				spin_unlock_irqrestore(&cs->lock, flags);
+				return;
+			}
+		} else {
+			err("control read: giving up after %d tries",
+			    ucs->retry_cmd_in);
+		}
+		error_reset(cs);
+	}
+
+	kfree(ucs->rcvbuf);
+	ucs->rcvbuf = NULL;
+	ucs->rcvbuf_size = 0;
+	spin_unlock_irqrestore(&cs->lock, flags);
+	if (have_data) {
+		dbg(DEBUG_INTR, "%s-->BH", __func__);
+		gigaset_schedule_event(cs);
+	}
+}
+
+/* read_iso_callback
+ * USB completion handler for B channel isochronous input
+ * called by the USB subsystem in interrupt context
+ * parameter:
+ *	urb	USB request block of completed request
+ *		urb->context = bc_state structure
+ */
+static void read_iso_callback(struct urb *urb, struct pt_regs *regs)
+{
+	struct bc_state *bcs;
+	struct bas_bc_state *ubc;
+	unsigned long flags;
+	int i, rc;
+
+	IFNULLRET(urb);
+	IFNULLRET(urb->context);
+	IFNULLRET(cardstate);
+
+	/* status codes not worth bothering the tasklet with */
+	if (unlikely(urb->status == -ENOENT || urb->status == -ECONNRESET ||
+	             urb->status == -EINPROGRESS)) {
+		dbg(DEBUG_ISO,
+		    "%s: %s", __func__, get_usb_statmsg(urb->status));
+		return;
+	}
+
+	bcs = (struct bc_state *) urb->context;
+	ubc = bcs->hw.bas;
+	IFNULLRET(ubc);
+
+	spin_lock_irqsave(&ubc->isoinlock, flags);
+	if (likely(ubc->isoindone == NULL)) {
+		/* pass URB to tasklet */
+		ubc->isoindone = urb;
+		tasklet_schedule(&ubc->rcvd_tasklet);
+	} else {
+		/* tasklet still busy, drop data and resubmit URB */
+		ubc->loststatus = urb->status;
+		for (i = 0; i < BAS_NUMFRAMES; i++) {
+			ubc->isoinlost += urb->iso_frame_desc[i].actual_length;
+			if (unlikely(urb->iso_frame_desc[i].status != 0 &&
+				     urb->iso_frame_desc[i].status != -EINPROGRESS)) {
+				ubc->loststatus = urb->iso_frame_desc[i].status;
+			}
+			urb->iso_frame_desc[i].status = 0;
+			urb->iso_frame_desc[i].actual_length = 0;
+		}
+		if (likely(atomic_read(&ubc->running))) {
+			urb->dev = bcs->cs->hw.bas->udev;	/* clobbered by USB subsystem */
+			urb->transfer_flags = URB_ISO_ASAP;
+			urb->number_of_packets = BAS_NUMFRAMES;
+			dbg(DEBUG_ISO, "%s: isoc read overrun/resubmit", __func__);
+			rc = usb_submit_urb(urb, SLAB_ATOMIC);
+			if (unlikely(rc != 0)) {
+				err("could not resubmit isochronous read URB: %s",
+				    get_usb_statmsg(rc));
+				dump_urb(DEBUG_ISO, "isoc read", urb);
+				error_hangup(bcs);
+			}
+		}
+	}
+	spin_unlock_irqrestore(&ubc->isoinlock, flags);
+}
+
+/* write_iso_callback
+ * USB completion handler for B channel isochronous output
+ * called by the USB subsystem in interrupt context
+ * parameter:
+ *	urb	USB request block of completed request
+ *		urb->context = isow_urbctx_t structure
+ */
+static void write_iso_callback(struct urb *urb, struct pt_regs *regs)
+{
+	struct isow_urbctx_t *ucx;
+	struct bas_bc_state *ubc;
+	unsigned long flags;
+
+	IFNULLRET(urb);
+	IFNULLRET(urb->context);
+	IFNULLRET(cardstate);
+
+	/* status codes not worth bothering the tasklet with */
+	if (unlikely(urb->status == -ENOENT || urb->status == -ECONNRESET ||
+	             urb->status == -EINPROGRESS)) {
+		dbg(DEBUG_ISO,
+		    "%s: %s", __func__, get_usb_statmsg(urb->status));
+		return;
+	}
+
+	/* pass URB context to tasklet */
+	ucx = (struct isow_urbctx_t *) urb->context;
+	IFNULLRET(ucx->bcs);
+	ubc = ucx->bcs->hw.bas;
+	IFNULLRET(ubc);
+
+	spin_lock_irqsave(&ubc->isooutlock, flags);
+	ubc->isooutovfl = ubc->isooutdone;
+	ubc->isooutdone = ucx;
+	spin_unlock_irqrestore(&ubc->isooutlock, flags);
+	tasklet_schedule(&ubc->sent_tasklet);
+}
+
+/* starturbs
+ * prepare and submit USB request blocks for isochronous input and output
+ * argument:
+ *	B channel control structure
+ * return value:
+ *	0 on success
+ *	< 0 on error (no URBs submitted)
+ */
+static int starturbs(struct bc_state *bcs)
+{
+	struct urb *urb;
+	struct bas_bc_state *ubc;
+	int j, k;
+	int rc;
+
+	IFNULLRETVAL(bcs, -EFAULT);
+	ubc = bcs->hw.bas;
+	IFNULLRETVAL(ubc, -EFAULT);
+
+	/* initialize L2 reception */
+	if (bcs->proto2 == ISDN_PROTO_L2_HDLC)
+		bcs->inputstate |= INS_flag_hunt;
+
+	/* submit all isochronous input URBs */
+	atomic_set(&ubc->running, 1);
+	for (k = 0; k < BAS_INURBS; k++) {
+		urb = ubc->isoinurbs[k];
+		if (!urb) {
+			err("isoinurbs[%d]==NULL", k);
+			rc = -EFAULT;
+			goto error;
+		}
+
+		urb->dev = bcs->cs->hw.bas->udev;
+		urb->pipe = usb_rcvisocpipe(urb->dev, 3 + 2 * bcs->channel);
+		urb->transfer_flags = URB_ISO_ASAP;
+		urb->transfer_buffer = ubc->isoinbuf + k * BAS_INBUFSIZE;
+		urb->transfer_buffer_length = BAS_INBUFSIZE;
+		urb->number_of_packets = BAS_NUMFRAMES;
+		urb->interval = BAS_FRAMETIME;
+		urb->complete = read_iso_callback;
+		urb->context = bcs;
+		for (j = 0; j < BAS_NUMFRAMES; j++) {
+			urb->iso_frame_desc[j].offset = j * BAS_MAXFRAME;
+			urb->iso_frame_desc[j].length = BAS_MAXFRAME;
+			urb->iso_frame_desc[j].status = 0;
+			urb->iso_frame_desc[j].actual_length = 0;
+		}
+
+		dump_urb(DEBUG_ISO, "Initial isoc read", urb);
+		if ((rc = usb_submit_urb(urb, SLAB_ATOMIC)) != 0) {
+			err("could not submit isochronous read URB %d: %s",
+			    k, get_usb_statmsg(rc));
+			goto error;
+		}
+	}
+
+	/* initialize L2 transmission */
+	gigaset_isowbuf_init(ubc->isooutbuf, PPP_FLAG);
+
+	/* set up isochronous output URBs for flag idling */
+	for (k = 0; k < BAS_OUTURBS; ++k) {
+		urb = ubc->isoouturbs[k].urb;
+		if (!urb) {
+			err("isoouturbs[%d].urb==NULL", k);
+			rc = -EFAULT;
+			goto error;
+		}
+		urb->dev = bcs->cs->hw.bas->udev;
+		urb->pipe = usb_sndisocpipe(urb->dev, 4 + 2 * bcs->channel);
+		urb->transfer_flags = URB_ISO_ASAP;
+		urb->transfer_buffer = ubc->isooutbuf->data;
+		urb->transfer_buffer_length = sizeof(ubc->isooutbuf->data);
+		urb->number_of_packets = BAS_NUMFRAMES;
+		urb->interval = BAS_FRAMETIME;
+		urb->complete = write_iso_callback;
+		urb->context = &ubc->isoouturbs[k];
+		for (j = 0; j < BAS_NUMFRAMES; ++j) {
+			urb->iso_frame_desc[j].offset = BAS_OUTBUFSIZE;
+			urb->iso_frame_desc[j].length = BAS_NORMFRAME;
+			urb->iso_frame_desc[j].status = 0;
+			urb->iso_frame_desc[j].actual_length = 0;
+		}
+		ubc->isoouturbs[k].limit = -1;
+	}
+
+	/* submit two URBs, keep third one */
+	for (k = 0; k < 2; ++k) {
+		dump_urb(DEBUG_ISO, "Initial isoc write", urb);
+		rc = usb_submit_urb(ubc->isoouturbs[k].urb, SLAB_ATOMIC);
+		if (rc != 0) {
+			err("could not submit isochronous write URB %d: %s",
+			    k, get_usb_statmsg(rc));
+			goto error;
+		}
+	}
+	dump_urb(DEBUG_ISO, "Initial isoc write (free)", urb);
+	ubc->isooutfree = &ubc->isoouturbs[2];
+	ubc->isooutdone = ubc->isooutovfl = NULL;
+	return 0;
+ error:
+	stopurbs(ubc);
+	return rc;
+}
+
+/* stopurbs
+ * cancel the USB request blocks for isochronous input and output
+ * errors are silently ignored
+ * argument:
+ *	B channel control structure
+ */
+static void stopurbs(struct bas_bc_state *ubc)
+{
+	int k, rc;
+
+	IFNULLRET(ubc);
+
+	atomic_set(&ubc->running, 0);
+
+	for (k = 0; k < BAS_INURBS; ++k) {
+		rc = usb_unlink_urb(ubc->isoinurbs[k]);
+		dbg(DEBUG_ISO, "%s: isoc input URB %d unlinked, result = %d",
+		    __func__, k, rc);
+	}
+
+	for (k = 0; k < BAS_OUTURBS; ++k) {
+		rc = usb_unlink_urb(ubc->isoouturbs[k].urb);
+		dbg(DEBUG_ISO, "%s: isoc output URB %d unlinked, result = %d",
+		    __func__, k, rc);
+	}
+}
+
+/* Isochronous Write - Bottom Half */
+/* =============================== */
+
+/* submit_iso_write_urb
+ * fill and submit the next isochronous write URB
+ * parameters:
+ *	bcs	B channel state structure
+ * return value:
+ *	number of frames submitted in URB
+ *	0 if URB not submitted because no data available (isooutbuf busy)
+ *	error code < 0 on error
+ */
+static int submit_iso_write_urb(struct isow_urbctx_t *ucx)
+{
+	struct urb *urb;
+	struct bas_bc_state *ubc;
+	struct usb_iso_packet_descriptor *ifd;
+	int corrbytes, nframe, rc;
+
+	IFNULLRETVAL(ucx, -EFAULT);
+	urb = ucx->urb;
+	IFNULLRETVAL(urb, -EFAULT);
+	IFNULLRETVAL(ucx->bcs, -EFAULT);
+	ubc = ucx->bcs->hw.bas;
+	IFNULLRETVAL(ubc, -EFAULT);
+
+	urb->dev = ucx->bcs->cs->hw.bas->udev;	/* clobbered by USB subsystem */
+	urb->transfer_flags = URB_ISO_ASAP;
+	urb->transfer_buffer = ubc->isooutbuf->data;
+	urb->transfer_buffer_length = sizeof(ubc->isooutbuf->data);
+
+	for (nframe = 0; nframe < BAS_NUMFRAMES; nframe++) {
+		ifd = &urb->iso_frame_desc[nframe];
+
+		/* compute frame length according to flow control */
+		ifd->length = BAS_NORMFRAME;
+		if ((corrbytes = atomic_read(&ubc->corrbytes)) != 0) {
+			dbg(DEBUG_ISO, "%s: corrbytes=%d", __func__, corrbytes);
+			if (corrbytes > BAS_HIGHFRAME - BAS_NORMFRAME)
+				corrbytes = BAS_HIGHFRAME - BAS_NORMFRAME;
+			else if (corrbytes < BAS_LOWFRAME - BAS_NORMFRAME)
+				corrbytes = BAS_LOWFRAME - BAS_NORMFRAME;
+			ifd->length += corrbytes;
+			atomic_add(-corrbytes, &ubc->corrbytes);
+		}
+		//dbg(DEBUG_ISO, "%s: frame %d length=%d", __func__, nframe, ifd->length);
+
+		/* retrieve block of data to send */
+		ifd->offset = gigaset_isowbuf_getbytes(ubc->isooutbuf, ifd->length);
+		if (ifd->offset < 0) {
+			if (ifd->offset == -EBUSY) {
+				dbg(DEBUG_ISO, "%s: buffer busy at frame %d",
+				    __func__, nframe);
+				/* tasklet will be restarted from gigaset_send_skb() */
+			} else {
+				err("%s: buffer error %d at frame %d",
+				    __func__, ifd->offset, nframe);
+				return ifd->offset;
+			}
+			break;
+		}
+		ucx->limit = atomic_read(&ubc->isooutbuf->nextread);
+		ifd->status = 0;
+		ifd->actual_length = 0;
+	}
+	if ((urb->number_of_packets = nframe) > 0) {
+		if ((rc = usb_submit_urb(urb, SLAB_ATOMIC)) != 0) {
+			err("could not submit isochronous write URB: %s",
+			    get_usb_statmsg(rc));
+			dump_urb(DEBUG_ISO, "isoc write", urb);
+			return rc;
+		}
+		++ubc->numsub;
+	}
+	return nframe;
+}
+
+/* write_iso_tasklet
+ * tasklet scheduled when an isochronous output URB from the Gigaset device
+ * has completed
+ * parameter:
+ *	data	B channel state structure
+ */
+static void write_iso_tasklet(unsigned long data)
+{
+	struct bc_state *bcs;
+	struct bas_bc_state *ubc;
+	struct cardstate *cs;
+	struct isow_urbctx_t *done, *next, *ovfl;
+	struct urb *urb;
+	struct usb_iso_packet_descriptor *ifd;
+	int offset;
+	unsigned long flags;
+	int i;
+	struct sk_buff *skb;
+	int len;
+
+	bcs = (struct bc_state *) data;
+	IFNULLRET(bcs);
+	ubc = bcs->hw.bas;
+	IFNULLRET(ubc);
+	cs = bcs->cs;
+	IFNULLRET(cs);
+
+	/* loop while completed URBs arrive in time */
+	for (;;) {
+		if (unlikely(!atomic_read(&cs->connected))) {
+			warn("%s: disconnected", __func__);
+			return;
+		}
+
+		if (unlikely(!(atomic_read(&ubc->running)))) {
+			dbg(DEBUG_ISO, "%s: not running", __func__);
+			return;
+		}
+
+		/* retrieve completed URBs */
+		spin_lock_irqsave(&ubc->isooutlock, flags);
+		done = ubc->isooutdone;
+		ubc->isooutdone = NULL;
+		ovfl = ubc->isooutovfl;
+		ubc->isooutovfl = NULL;
+		spin_unlock_irqrestore(&ubc->isooutlock, flags);
+		if (ovfl) {
+			err("isochronous write buffer underrun - buy a faster machine :-)");
+			error_hangup(bcs);
+			break;
+		}
+		if (!done)
+			break;
+
+		/* submit free URB if available */
+		spin_lock_irqsave(&ubc->isooutlock, flags);
+		next = ubc->isooutfree;
+		ubc->isooutfree = NULL;
+		spin_unlock_irqrestore(&ubc->isooutlock, flags);
+		if (next) {
+			if (submit_iso_write_urb(next) <= 0) {
+				/* could not submit URB, put it back */
+				spin_lock_irqsave(&ubc->isooutlock, flags);
+				if (ubc->isooutfree == NULL) {
+					ubc->isooutfree = next;
+					next = NULL;
+				}
+				spin_unlock_irqrestore(&ubc->isooutlock, flags);
+				if (next) {
+					/* couldn't put it back */
+					err("losing isochronous write URB");
+					error_hangup(bcs);
+				}
+			}
+		}
+
+		/* process completed URB */
+		urb = done->urb;
+		switch (urb->status) {
+		case 0:				/* normal completion */
+			break;
+		case -EXDEV:			/* inspect individual frames */
+			/* assumptions (for lack of documentation):
+			 * - actual_length bytes of the frame in error are successfully sent
+			 * - all following frames are not sent at all
+			 */
+			dbg(DEBUG_ISO, "%s: URB partially completed", __func__);
+			offset = done->limit;	/* just in case */
+			for (i = 0; i < BAS_NUMFRAMES; i++) {
+				ifd = &urb->iso_frame_desc[i];
+				if (ifd->status ||
+				    ifd->actual_length != ifd->length) {
+					warn("isochronous write: frame %d: %s, "
+					     "only %d of %d bytes sent",
+					     i, get_usb_statmsg(ifd->status),
+					     ifd->actual_length, ifd->length);
+					offset = (ifd->offset +
+					          ifd->actual_length)
+					         % BAS_OUTBUFSIZE;
+					break;
+				}
+			}
+#ifdef CONFIG_GIGASET_DEBUG
+			/* check assumption on remaining frames */
+			for (; i < BAS_NUMFRAMES; i++) {
+				ifd = &urb->iso_frame_desc[i];
+				if (ifd->status != -EINPROGRESS
+				    || ifd->actual_length != 0) {
+					warn("isochronous write: frame %d: %s, "
+					     "%d of %d bytes sent",
+					     i, get_usb_statmsg(ifd->status),
+					     ifd->actual_length, ifd->length);
+					offset = (ifd->offset +
+					          ifd->actual_length)
+					         % BAS_OUTBUFSIZE;
+					break;
+				}
+			}
+#endif
+			break;
+		case -EPIPE:			//FIXME is this the code for "underrun"?
+			err("isochronous write stalled");
+			error_hangup(bcs);
+			break;
+		default:			/* severe trouble */
+			warn("isochronous write: %s",
+			     get_usb_statmsg(urb->status));
+		}
+
+		/* mark the write buffer area covered by this URB as free */
+		if (done->limit >= 0)
+			atomic_set(&ubc->isooutbuf->read, done->limit);
+
+		/* mark URB as free */
+		spin_lock_irqsave(&ubc->isooutlock, flags);
+		next = ubc->isooutfree;
+		ubc->isooutfree = done;
+		spin_unlock_irqrestore(&ubc->isooutlock, flags);
+		if (next) {
+			/* only one URB still active - resubmit one */
+			if (submit_iso_write_urb(next) <= 0) {
+				/* couldn't submit */
+				error_hangup(bcs);
+			}
+		}
+	}
+
+	/* process queued SKBs */
+	while ((skb = skb_dequeue(&bcs->squeue))) {
+		/* copy to output buffer, doing L2 encapsulation */
+		len = skb->len;
+		if (gigaset_isoc_buildframe(bcs, skb->data, len) == -EAGAIN) {
+			/* insufficient buffer space, push back onto queue */
+			skb_queue_head(&bcs->squeue, skb);
+			dbg(DEBUG_ISO, "%s: skb requeued, qlen=%d",
+			    __func__, skb_queue_len(&bcs->squeue));
+			break;
+		}
+		skb_pull(skb, len);
+		gigaset_skb_sent(bcs, skb);
+		dev_kfree_skb_any(skb);
+	}
+}
+
+/* Isochronous Read - Bottom Half */
+/* ============================== */
+
+/* read_iso_tasklet
+ * tasklet scheduled when an isochronous input URB from the Gigaset device
+ * has completed
+ * parameter:
+ *	data	B channel state structure
+ */
+static void read_iso_tasklet(unsigned long data)
+{
+	struct bc_state *bcs;
+	struct bas_bc_state *ubc;
+	struct cardstate *cs;
+	struct urb *urb;
+	char *rcvbuf;
+	unsigned long flags;
+	int totleft, numbytes, offset, frame, rc;
+
+	bcs = (struct bc_state *) data;
+	IFNULLRET(bcs);
+	ubc = bcs->hw.bas;
+	IFNULLRET(ubc);
+	cs = bcs->cs;
+	IFNULLRET(cs);
+
+	/* loop while more completed URBs arrive in the meantime */
+	for (;;) {
+		if (!atomic_read(&cs->connected)) {
+			warn("%s: disconnected", __func__);
+			return;
+		}
+
+		/* retrieve URB */
+		spin_lock_irqsave(&ubc->isoinlock, flags);
+		if (!(urb = ubc->isoindone)) {
+			spin_unlock_irqrestore(&ubc->isoinlock, flags);
+			return;
+		}
+		ubc->isoindone = NULL;
+		if (unlikely(ubc->loststatus != -EINPROGRESS)) {
+			warn("isochronous read overrun, dropped URB with status: %s, %d bytes lost",
+			     get_usb_statmsg(ubc->loststatus), ubc->isoinlost);
+			ubc->loststatus = -EINPROGRESS;
+		}
+		spin_unlock_irqrestore(&ubc->isoinlock, flags);
+
+		if (unlikely(!(atomic_read(&ubc->running)))) {
+			dbg(DEBUG_ISO, "%s: channel not running, dropped URB with status: %s",
+			    __func__, get_usb_statmsg(urb->status));
+			return;
+		}
+
+		switch (urb->status) {
+		case 0:				/* normal completion */
+			break;
+		case -EXDEV:			/* inspect individual frames (we do that anyway) */
+			dbg(DEBUG_ISO, "%s: URB partially completed", __func__);
+			break;
+		case -ENOENT:
+		case -ECONNRESET:
+			dbg(DEBUG_ISO, "%s: URB canceled", __func__);
+			continue;		/* -> skip */
+		case -EINPROGRESS:		/* huh? */
+			dbg(DEBUG_ISO, "%s: URB still pending", __func__);
+			continue;		/* -> skip */
+		case -EPIPE:
+			err("isochronous read stalled");
+			error_hangup(bcs);
+			continue;		/* -> skip */
+		default:			/* severe trouble */
+			warn("isochronous read: %s",
+			     get_usb_statmsg(urb->status));
+			goto error;
+		}
+
+		rcvbuf = urb->transfer_buffer;
+		totleft = urb->actual_length;
+		for (frame = 0; totleft > 0 && frame < BAS_NUMFRAMES; frame++) {
+			if (unlikely(urb->iso_frame_desc[frame].status)) {
+				warn("isochronous read: frame %d: %s",
+				     frame, get_usb_statmsg(urb->iso_frame_desc[frame].status));
+				break;
+			}
+			numbytes = urb->iso_frame_desc[frame].actual_length;
+			if (unlikely(numbytes > BAS_MAXFRAME)) {
+				warn("isochronous read: frame %d: numbytes (%d) > BAS_MAXFRAME",
+				     frame, numbytes);
+				break;
+			}
+			if (unlikely(numbytes > totleft)) {
+				warn("isochronous read: frame %d: numbytes (%d) > totleft (%d)",
+				     frame, numbytes, totleft);
+				break;
+			}
+			offset = urb->iso_frame_desc[frame].offset;
+			if (unlikely(offset + numbytes > BAS_INBUFSIZE)) {
+				warn("isochronous read: frame %d: offset (%d) + numbytes (%d) > BAS_INBUFSIZE",
+				     frame, offset, numbytes);
+				break;
+			}
+			gigaset_isoc_receive(rcvbuf + offset, numbytes, bcs);
+			totleft -= numbytes;
+		}
+		if (unlikely(totleft > 0))
+			warn("isochronous read: %d data bytes missing",
+			     totleft);
+
+	error:
+		/* URB processed, resubmit */
+		for (frame = 0; frame < BAS_NUMFRAMES; frame++) {
+			urb->iso_frame_desc[frame].status = 0;
+			urb->iso_frame_desc[frame].actual_length = 0;
+		}
+		urb->dev = bcs->cs->hw.bas->udev;	/* clobbered by USB subsystem */
+		urb->transfer_flags = URB_ISO_ASAP;
+		urb->number_of_packets = BAS_NUMFRAMES;
+		if ((rc = usb_submit_urb(urb, SLAB_ATOMIC)) != 0) {
+			err("could not resubmit isochronous read URB: %s",
+			    get_usb_statmsg(rc));
+			dump_urb(DEBUG_ISO, "resubmit iso read", urb);
+			error_hangup(bcs);
+		}
+	}
+}
+
+/* Channel Operations */
+/* ================== */
+
+/* req_timeout
+ * timeout routine for control output request
+ * argument:
+ *	B channel control structure
+ */
+static void req_timeout(unsigned long data)
+{
+	struct bc_state *bcs = (struct bc_state *) data;
+	struct bas_cardstate *ucs;
+	int pending;
+	unsigned long flags;
+
+	IFNULLRET(bcs);
+	IFNULLRET(bcs->cs);
+	ucs = bcs->cs->hw.bas;
+	IFNULLRET(ucs);
+
+	check_pending(ucs);
+
+	spin_lock_irqsave(&ucs->lock, flags);
+	pending = ucs->pending;
+	ucs->pending = 0;
+	spin_unlock_irqrestore(&ucs->lock, flags);
+
+	switch (pending) {
+	case 0:					/* no pending request */
+		dbg(DEBUG_USBREQ, "%s: no request pending", __func__);
+		break;
+
+	case HD_OPEN_ATCHANNEL:
+		err("timeout opening AT channel");
+		error_reset(bcs->cs);
+		break;
+
+	case HD_OPEN_B2CHANNEL:
+	case HD_OPEN_B1CHANNEL:
+		err("timeout opening channel %d", bcs->channel + 1);
+		error_hangup(bcs);
+		break;
+
+	case HD_CLOSE_ATCHANNEL:
+		err("timeout closing AT channel");
+		//wake_up_interruptible(cs->initwait);
+		//FIXME need own wait queue?
+		break;
+
+	case HD_CLOSE_B2CHANNEL:
+	case HD_CLOSE_B1CHANNEL:
+		err("timeout closing channel %d", bcs->channel + 1);
+		break;
+
+	default:
+		warn("request 0x%02x timed out, clearing", pending);
+	}
+}
+
+/* write_ctrl_callback
+ * USB completion handler for control pipe output
+ * called by the USB subsystem in interrupt context
+ * parameter:
+ *	urb	USB request block of completed request
+ *		urb->context = hardware specific controller state structure
+ */
+static void write_ctrl_callback(struct urb *urb, struct pt_regs *regs)
+{
+	struct bas_cardstate *ucs;
+	unsigned long flags;
+
+	IFNULLRET(urb);
+	IFNULLRET(urb->context);
+	IFNULLRET(cardstate);
+
+	ucs = (struct bas_cardstate *) urb->context;
+	spin_lock_irqsave(&ucs->lock, flags);
+	if (urb->status && ucs->pending) {
+		err("control request 0x%02x failed: %s",
+		    ucs->pending, get_usb_statmsg(urb->status));
+		del_timer(&ucs->timer_ctrl);
+		ucs->pending = 0;
+	}
+	/* individual handling of specific request types */
+	switch (ucs->pending) {
+	case HD_DEVICE_INIT_ACK:		/* no reply expected */
+		ucs->pending = 0;
+		break;
+	}
+	spin_unlock_irqrestore(&ucs->lock, flags);
+}
+
+/* req_submit
+ * submit a control output request without message buffer to the Gigaset base
+ * and optionally start a timeout
+ * parameters:
+ *	bcs	B channel control structure
+ *	req	control request code (HD_*)
+ *	val	control request parameter value (set to 0 if unused)
+ *	timeout	timeout in seconds (0: no timeout)
+ * return value:
+ *	0 on success
+ *	-EINVAL if a NULL pointer is encountered somewhere
+ *	-EBUSY if another request is pending
+ *	any URB submission error code
+ */
+static int req_submit(struct bc_state *bcs, int req, int val, int timeout)
+{
+	struct bas_cardstate *ucs;
+	int ret;
+	unsigned long flags;
+
+	IFNULLRETVAL(bcs, -EINVAL);
+	IFNULLRETVAL(bcs->cs, -EINVAL);
+	ucs = bcs->cs->hw.bas;
+	IFNULLRETVAL(ucs, -EINVAL);
+	IFNULLRETVAL(ucs->urb_ctrl, -EINVAL);
+
+	dbg(DEBUG_USBREQ, "-------> 0x%02x (%d)", req, val);
+
+	spin_lock_irqsave(&ucs->lock, flags);
+	if (ucs->pending) {
+		spin_unlock_irqrestore(&ucs->lock, flags);
+		err("submission of request 0x%02x failed: request 0x%02x still pending",
+		    req, ucs->pending);
+		return -EBUSY;
+	}
+	if (ucs->urb_ctrl->status == -EINPROGRESS) {
+		spin_unlock_irqrestore(&ucs->lock, flags);
+		err("could not submit request 0x%02x: URB busy", req);
+		return -EBUSY;
+	}
+
+	ucs->dr_ctrl.bRequestType = OUT_VENDOR_REQ;
+	ucs->dr_ctrl.bRequest = req;
+	ucs->dr_ctrl.wValue = cpu_to_le16(val);
+	ucs->dr_ctrl.wIndex = 0;
+	ucs->dr_ctrl.wLength = 0;
+	usb_fill_control_urb(ucs->urb_ctrl, ucs->udev,
+                             usb_sndctrlpipe(ucs->udev, 0),
+                             (unsigned char*) &ucs->dr_ctrl, NULL, 0,
+                             write_ctrl_callback, ucs);
+	if ((ret = usb_submit_urb(ucs->urb_ctrl, SLAB_ATOMIC)) != 0) {
+		err("could not submit request 0x%02x: %s",
+		    req, get_usb_statmsg(ret));
+		spin_unlock_irqrestore(&ucs->lock, flags);
+		return ret;
+	}
+	ucs->pending = req;
+
+	if (timeout > 0) {
+		dbg(DEBUG_USBREQ, "setting timeout of %d/10 secs", timeout);
+		ucs->timer_ctrl.expires = jiffies + timeout * HZ / 10;
+		ucs->timer_ctrl.data = (unsigned long) bcs;
+		ucs->timer_ctrl.function = req_timeout;
+		add_timer(&ucs->timer_ctrl);
+	}
+
+	spin_unlock_irqrestore(&ucs->lock, flags);
+	return 0;
+}
+
+/* gigaset_init_bchannel
+ * called by common.c to connect a B channel
+ * initialize isochronous I/O and tell the Gigaset base to open the channel
+ * argument:
+ *	B channel control structure
+ * return value:
+ *	0 on success, error code < 0 on error
+ */
+static int gigaset_init_bchannel(struct bc_state *bcs)
+{
+	int req, ret;
+
+	IFNULLRETVAL(bcs, -EINVAL);
+
+	if ((ret = starturbs(bcs)) < 0) {
+		err("could not start isochronous I/O for channel %d",
+		    bcs->channel + 1);
+		error_hangup(bcs);
+		return ret;
+	}
+
+	req = bcs->channel ? HD_OPEN_B2CHANNEL : HD_OPEN_B1CHANNEL;
+	if ((ret = req_submit(bcs, req, 0, BAS_TIMEOUT)) < 0) {
+		err("could not open channel %d: %s",
+		    bcs->channel + 1, get_usb_statmsg(ret));
+		stopurbs(bcs->hw.bas);
+		error_hangup(bcs);
+	}
+	return ret;
+}
+
+/* gigaset_close_bchannel
+ * called by common.c to disconnect a B channel
+ * tell the Gigaset base to close the channel
+ * stopping isochronous I/O and LL notification will be done when the
+ * acknowledgement for the close arrives
+ * argument:
+ *	B channel control structure
+ * return value:
+ *	0 on success, error code < 0 on error
+ */
+static int gigaset_close_bchannel(struct bc_state *bcs)
+{
+	int req, ret;
+
+	IFNULLRETVAL(bcs, -EINVAL);
+
+	if (!(atomic_read(&bcs->cs->hw.bas->basstate) &
+	      (bcs->channel ? BS_B2OPEN : BS_B1OPEN))) {
+		/* channel not running: just signal common.c */
+		gigaset_bchannel_down(bcs);
+		return 0;
+	}
+
+	req = bcs->channel ? HD_CLOSE_B2CHANNEL : HD_CLOSE_B1CHANNEL;
+	if ((ret = req_submit(bcs, req, 0, BAS_TIMEOUT)) < 0)
+		err("could not submit HD_CLOSE_BxCHANNEL request: %s",
+		    get_usb_statmsg(ret));
+	return ret;
+}
+
+/* Device Operations */
+/* ================= */
+
+/* complete_cb
+ * unqueue first command buffer from queue, waking any sleepers
+ * must be called with cs->cmdlock held
+ * parameter:
+ *	cs	controller state structure
+ */
+static void complete_cb(struct cardstate *cs)
+{
+	struct cmdbuf_t *cb;
+
+	IFNULLRET(cs);
+	cb = cs->cmdbuf;
+	IFNULLRET(cb);
+
+	/* unqueue completed buffer */
+	cs->cmdbytes -= cs->curlen;
+	dbg(DEBUG_TRANSCMD | DEBUG_LOCKCMD,
+	    "write_command: sent %u bytes, %u left",
+	    cs->curlen, cs->cmdbytes);
+	if ((cs->cmdbuf = cb->next) != NULL) {
+		cs->cmdbuf->prev = NULL;
+		cs->curlen = cs->cmdbuf->len;
+	} else {
+		cs->lastcmdbuf = NULL;
+		cs->curlen = 0;
+	}
+
+	if (cb->wake_tasklet)
+		tasklet_schedule(cb->wake_tasklet);
+
+	kfree(cb);
+}
+
+static int atwrite_submit(struct cardstate *cs, unsigned char *buf, int len);
+
+/* write_command_callback
+ * USB completion handler for AT command transmission
+ * called by the USB subsystem in interrupt context
+ * parameter:
+ *	urb	USB request block of completed request
+ *		urb->context = controller state structure
+ */
+static void write_command_callback(struct urb *urb, struct pt_regs *regs)
+{
+	struct cardstate *cs;
+	unsigned long flags;
+	struct bas_cardstate *ucs;
+
+	IFNULLRET(urb);
+	cs = (struct cardstate *) urb->context;
+	IFNULLRET(cs);
+	ucs = cs->hw.bas;
+	IFNULLRET(ucs);
+
+	/* check status */
+	switch (urb->status) {
+	case 0:					/* normal completion */
+		break;
+	case -ENOENT:			/* canceled */
+	case -ECONNRESET:		/* canceled (async) */
+	case -EINPROGRESS:		/* pending */
+		/* ignore silently */
+		dbg(DEBUG_USBREQ,
+		    "%s: %s", __func__, get_usb_statmsg(urb->status));
+		return;
+	default:				/* any failure */
+		if (++ucs->retry_cmd_out > BAS_RETRY) {
+			warn("command write: %s, giving up after %d retries",
+			     get_usb_statmsg(urb->status), ucs->retry_cmd_out);
+			break;
+		}
+		if (cs->cmdbuf == NULL) {
+			warn("command write: %s, cannot retry - cmdbuf gone",
+			     get_usb_statmsg(urb->status));
+			break;
+		}
+		notice("command write: %s, retry %d",
+		       get_usb_statmsg(urb->status), ucs->retry_cmd_out);
+		if (atwrite_submit(cs, cs->cmdbuf->buf, cs->cmdbuf->len) >= 0)
+			/* resubmitted - bypass regular exit block */
+			return;
+		/* command send failed, assume base still waiting */
+		update_basstate(ucs, BS_ATREADY, 0);
+	}
+
+	spin_lock_irqsave(&cs->cmdlock, flags);
+	if (cs->cmdbuf != NULL)
+		complete_cb(cs);
+	spin_unlock_irqrestore(&cs->cmdlock, flags);
+}
+
+/* atrdy_timeout
+ * timeout routine for AT command transmission
+ * argument:
+ *	controller state structure
+ */
+static void atrdy_timeout(unsigned long data)
+{
+	struct cardstate *cs = (struct cardstate *) data;
+	struct bas_cardstate *ucs;
+
+	IFNULLRET(cs);
+	ucs = cs->hw.bas;
+	IFNULLRET(ucs);
+
+	warn("timeout waiting for HD_READY_SEND_ATDATA");
+
+	/* fake the missing signal - what else can I do? */
+	update_basstate(ucs, BS_ATREADY, BS_ATTIMER);
+	start_cbsend(cs);
+}
+
+/* atwrite_submit
+ * submit an HD_WRITE_ATMESSAGE command URB
+ * parameters:
+ *	cs	controller state structure
+ *	buf	buffer containing command to send
+ *	len	length of command to send
+ * return value:
+ *	0 on success
+ *	-EFAULT if a NULL pointer is encountered somewhere
+ *	-EBUSY if another request is pending
+ *	any URB submission error code
+ */
+static int atwrite_submit(struct cardstate *cs, unsigned char *buf, int len)
+{
+	struct bas_cardstate *ucs;
+	int ret;
+
+	IFNULLRETVAL(cs, -EFAULT);
+	ucs = cs->hw.bas;
+	IFNULLRETVAL(ucs, -EFAULT);
+	IFNULLRETVAL(ucs->urb_cmd_out, -EFAULT);
+
+	dbg(DEBUG_USBREQ, "-------> HD_WRITE_ATMESSAGE (%d)", len);
+
+	if (ucs->urb_cmd_out->status == -EINPROGRESS) {
+		err("could not submit HD_WRITE_ATMESSAGE: URB busy");
+		return -EBUSY;
+	}
+
+	ucs->dr_cmd_out.bRequestType = OUT_VENDOR_REQ;
+	ucs->dr_cmd_out.bRequest = HD_WRITE_ATMESSAGE;
+	ucs->dr_cmd_out.wValue = 0;
+	ucs->dr_cmd_out.wIndex = 0;
+	ucs->dr_cmd_out.wLength = cpu_to_le16(len);
+	usb_fill_control_urb(ucs->urb_cmd_out, ucs->udev,
+			     usb_sndctrlpipe(ucs->udev, 0),
+			     (unsigned char*) &ucs->dr_cmd_out, buf, len,
+			     write_command_callback, cs);
+
+	if ((ret = usb_submit_urb(ucs->urb_cmd_out, SLAB_ATOMIC)) != 0) {
+		err("could not submit HD_WRITE_ATMESSAGE: %s",
+		    get_usb_statmsg(ret));
+		return ret;
+	}
+
+	/* submitted successfully */
+	update_basstate(ucs, 0, BS_ATREADY);
+
+	/* start timeout if necessary */
+	if (!(atomic_read(&ucs->basstate) & BS_ATTIMER)) {
+		dbg(DEBUG_OUTPUT,
+		    "setting ATREADY timeout of %d/10 secs", ATRDY_TIMEOUT);
+		ucs->timer_atrdy.expires = jiffies + ATRDY_TIMEOUT * HZ / 10;
+		ucs->timer_atrdy.data = (unsigned long) cs;
+		ucs->timer_atrdy.function = atrdy_timeout;
+		add_timer(&ucs->timer_atrdy);
+		update_basstate(ucs, BS_ATTIMER, 0);
+	}
+	return 0;
+}
+
+/* start_cbsend
+ * start transmission of AT command queue if necessary
+ * parameter:
+ *	cs		controller state structure
+ * return value:
+ *	0 on success
+ *	error code < 0 on error
+ */
+static int start_cbsend(struct cardstate *cs)
+{
+	struct cmdbuf_t *cb;
+	struct bas_cardstate *ucs;
+	unsigned long flags;
+	int rc;
+	int retval = 0;
+
+	IFNULLRETVAL(cs, -EFAULT);
+	ucs = cs->hw.bas;
+	IFNULLRETVAL(ucs, -EFAULT);
+
+	/* check if AT channel is open */
+	if (!(atomic_read(&ucs->basstate) & BS_ATOPEN)) {
+		dbg(DEBUG_TRANSCMD | DEBUG_LOCKCMD, "AT channel not open");
+		rc = req_submit(cs->bcs, HD_OPEN_ATCHANNEL, 0, BAS_TIMEOUT);
+		if (rc < 0) {
+			err("could not open AT channel");
+			/* flush command queue */
+			spin_lock_irqsave(&cs->cmdlock, flags);
+			while (cs->cmdbuf != NULL)
+				complete_cb(cs);
+			spin_unlock_irqrestore(&cs->cmdlock, flags);
+		}
+		return rc;
+	}
+
+	/* try to send first command in queue */
+	spin_lock_irqsave(&cs->cmdlock, flags);
+
+	while ((cb = cs->cmdbuf) != NULL &&
+	       atomic_read(&ucs->basstate) & BS_ATREADY) {
+		ucs->retry_cmd_out = 0;
+		rc = atwrite_submit(cs, cb->buf, cb->len);
+		if (unlikely(rc)) {
+			retval = rc;
+			complete_cb(cs);
+		}
+	}
+
+	spin_unlock_irqrestore(&cs->cmdlock, flags);
+	return retval;
+}
+
+/* gigaset_write_cmd
+ * This function is called by the device independent part of the driver
+ * to transmit an AT command string to the Gigaset device.
+ * It encapsulates the device specific method for transmission over the
+ * direct USB connection to the base.
+ * The command string is added to the queue of commands to send, and
+ * USB transmission is started if necessary.
+ * parameters:
+ *	cs		controller state structure
+ *	buf		command string to send
+ *	len		number of bytes to send (max. IF_WRITEBUF)
+ *	wake_tasklet	tasklet to run when transmission is completed (NULL if none)
+ * return value:
+ *	number of bytes queued on success
+ *	error code < 0 on error
+ */
+static int gigaset_write_cmd(struct cardstate *cs,
+                             const unsigned char *buf, int len,
+                             struct tasklet_struct *wake_tasklet)
+{
+	struct cmdbuf_t *cb;
+	unsigned long flags;
+	int status;
+
+	gigaset_dbg_buffer(atomic_read(&cs->mstate) != MS_LOCKED ?
+	                     DEBUG_TRANSCMD : DEBUG_LOCKCMD,
+	                   "CMD Transmit", len, buf, 0);
+
+	if (!atomic_read(&cs->connected)) {
+		err("%s: not connected", __func__);
+		return -ENODEV;
+	}
+
+	if (len <= 0)
+		return 0;			/* nothing to do */
+
+	if (len > IF_WRITEBUF)
+		len = IF_WRITEBUF;
+	if (!(cb = kmalloc(sizeof(struct cmdbuf_t) + len, GFP_ATOMIC))) {
+		err("%s: out of memory", __func__);
+		return -ENOMEM;
+	}
+
+	memcpy(cb->buf, buf, len);
+	cb->len = len;
+	cb->offset = 0;
+	cb->next = NULL;
+	cb->wake_tasklet = wake_tasklet;
+
+	spin_lock_irqsave(&cs->cmdlock, flags);
+	cb->prev = cs->lastcmdbuf;
+	if (cs->lastcmdbuf)
+		cs->lastcmdbuf->next = cb;
+	else {
+		cs->cmdbuf = cb;
+		cs->curlen = len;
+	}
+	cs->cmdbytes += len;
+	cs->lastcmdbuf = cb;
+	spin_unlock_irqrestore(&cs->cmdlock, flags);
+
+	status = start_cbsend(cs);
+
+	return status < 0 ? status : len;
+}
+
+/* gigaset_write_room
+ * tty_driver.write_room interface routine
+ * return number of characters the driver will accept to be written via gigaset_write_cmd
+ * parameter:
+ *	controller state structure
+ * return value:
+ *	number of characters
+ */
+static int gigaset_write_room(struct cardstate *cs)
+{
+	return IF_WRITEBUF;
+}
+
+/* gigaset_chars_in_buffer
+ * tty_driver.chars_in_buffer interface routine
+ * return number of characters waiting to be sent
+ * parameter:
+ *	controller state structure
+ * return value:
+ *	number of characters
+ */
+static int gigaset_chars_in_buffer(struct cardstate *cs)
+{
+	unsigned long flags;
+	unsigned bytes;
+
+	spin_lock_irqsave(&cs->cmdlock, flags);
+	bytes = cs->cmdbytes;
+	spin_unlock_irqrestore(&cs->cmdlock, flags);
+
+	return bytes;
+}
+
+/* gigaset_brkchars
+ * implementation of ioctl(GIGASET_BRKCHARS)
+ * parameter:
+ *	controller state structure
+ * return value:
+ *	-EINVAL (unimplemented function)
+ */
+static int gigaset_brkchars(struct cardstate *cs, const unsigned char buf[6])
+{
+	return -EINVAL;
+}
+
+
+/* Device Initialization/Shutdown */
+/* ============================== */
+
+/* Free hardware dependent part of the B channel structure
+ * parameter:
+ *	bcs	B channel structure
+ * return value:
+ *	!=0 on success
+ */
+static int gigaset_freebcshw(struct bc_state *bcs)
+{
+	if (!bcs->hw.bas)
+		return 0;
+
+	if (bcs->hw.bas->isooutbuf)
+		kfree(bcs->hw.bas->isooutbuf);
+	kfree(bcs->hw.bas);
+	bcs->hw.bas = NULL;
+	return 1;
+}
+
+/* Initialize hardware dependent part of the B channel structure
+ * parameter:
+ *	bcs	B channel structure
+ * return value:
+ *	!=0 on success
+ */
+static int gigaset_initbcshw(struct bc_state *bcs)
+{
+	int i;
+	struct bas_bc_state *ubc;
+
+	bcs->hw.bas = ubc = kmalloc(sizeof(struct bas_bc_state), GFP_KERNEL);
+	if (!ubc) {
+		err("could not allocate bas_bc_state");
+		return 0;
+	}
+
+	atomic_set(&ubc->running, 0);
+	atomic_set(&ubc->corrbytes, 0);
+	spin_lock_init(&ubc->isooutlock);
+	for (i = 0; i < BAS_OUTURBS; ++i) {
+		ubc->isoouturbs[i].urb = NULL;
+		ubc->isoouturbs[i].bcs = bcs;
+	}
+	ubc->isooutdone = ubc->isooutfree = ubc->isooutovfl = NULL;
+	ubc->numsub = 0;
+	if (!(ubc->isooutbuf = kmalloc(sizeof(struct isowbuf_t), GFP_KERNEL))) {
+		err("could not allocate isochronous output buffer");
+		kfree(ubc);
+		bcs->hw.bas = NULL;
+		return 0;
+	}
+	tasklet_init(&ubc->sent_tasklet,
+	             &write_iso_tasklet, (unsigned long) bcs);
+
+	spin_lock_init(&ubc->isoinlock);
+	for (i = 0; i < BAS_INURBS; ++i)
+		ubc->isoinurbs[i] = NULL;
+	ubc->isoindone = NULL;
+	ubc->loststatus = -EINPROGRESS;
+	ubc->isoinlost = 0;
+	ubc->seqlen = 0;
+	ubc->inbyte = 0;
+	ubc->inbits = 0;
+	ubc->goodbytes = 0;
+	ubc->alignerrs = 0;
+	ubc->fcserrs = 0;
+	ubc->frameerrs = 0;
+	ubc->giants = 0;
+	ubc->runts = 0;
+	ubc->aborts = 0;
+	ubc->shared0s = 0;
+	ubc->stolen0s = 0;
+	tasklet_init(&ubc->rcvd_tasklet,
+	             &read_iso_tasklet, (unsigned long) bcs);
+	return 1;
+}
+
+static void gigaset_reinitbcshw(struct bc_state *bcs)
+{
+	struct bas_bc_state *ubc = bcs->hw.bas;
+
+	atomic_set(&bcs->hw.bas->running, 0);
+	atomic_set(&bcs->hw.bas->corrbytes, 0);
+	bcs->hw.bas->numsub = 0;
+	spin_lock_init(&ubc->isooutlock);
+	spin_lock_init(&ubc->isoinlock);
+	ubc->loststatus = -EINPROGRESS;
+}
+
+static void gigaset_freecshw(struct cardstate *cs)
+{
+	struct bas_cardstate *ucs = cs->hw.bas;
+
+	del_timer(&ucs->timer_ctrl);
+	del_timer(&ucs->timer_atrdy);
+	del_timer(&ucs->timer_cmd_in);
+
+	kfree(cs->hw.bas);
+}
+
+static int gigaset_initcshw(struct cardstate *cs)
+{
+	struct bas_cardstate *ucs;
+
+	cs->hw.bas = ucs = kmalloc(sizeof *ucs, GFP_KERNEL);
+	if (!ucs)
+		return 0;
+
+	ucs->urb_cmd_in = NULL;
+	ucs->urb_cmd_out = NULL;
+	ucs->rcvbuf = NULL;
+	ucs->rcvbuf_size = 0;
+
+	spin_lock_init(&ucs->lock);
+	ucs->pending = 0;
+
+	atomic_set(&ucs->basstate, 0);
+	init_timer(&ucs->timer_ctrl);
+	init_timer(&ucs->timer_atrdy);
+	init_timer(&ucs->timer_cmd_in);
+
+	return 1;
+}
+
+/* freeurbs
+ * unlink and deallocate all URBs unconditionally
+ * caller must make sure that no commands are still in progress
+ * parameter:
+ *	cs	controller state structure
+ */
+static void freeurbs(struct cardstate *cs)
+{
+	struct bas_cardstate *ucs;
+	struct bas_bc_state *ubc;
+	int i, j;
+
+	IFNULLRET(cs);
+	ucs = cs->hw.bas;
+	IFNULLRET(ucs);
+
+	for (j = 0; j < 2; ++j) {
+		ubc = cs->bcs[j].hw.bas;
+		IFNULLCONT(ubc);
+		for (i = 0; i < BAS_OUTURBS; ++i)
+			if (ubc->isoouturbs[i].urb) {
+				usb_kill_urb(ubc->isoouturbs[i].urb);
+				dbg(DEBUG_INIT,
+				    "%s: isoc output URB %d/%d unlinked",
+				    __func__, j, i);
+				usb_free_urb(ubc->isoouturbs[i].urb);
+				ubc->isoouturbs[i].urb = NULL;
+			}
+		for (i = 0; i < BAS_INURBS; ++i)
+			if (ubc->isoinurbs[i]) {
+				usb_kill_urb(ubc->isoinurbs[i]);
+				dbg(DEBUG_INIT,
+				    "%s: isoc input URB %d/%d unlinked",
+				    __func__, j, i);
+				usb_free_urb(ubc->isoinurbs[i]);
+				ubc->isoinurbs[i] = NULL;
+			}
+	}
+	if (ucs->urb_int_in) {
+		usb_kill_urb(ucs->urb_int_in);
+		dbg(DEBUG_INIT, "%s: interrupt input URB unlinked", __func__);
+		usb_free_urb(ucs->urb_int_in);
+		ucs->urb_int_in = NULL;
+	}
+	if (ucs->urb_cmd_out) {
+		usb_kill_urb(ucs->urb_cmd_out);
+		dbg(DEBUG_INIT, "%s: command output URB unlinked", __func__);
+		usb_free_urb(ucs->urb_cmd_out);
+		ucs->urb_cmd_out = NULL;
+	}
+	if (ucs->urb_cmd_in) {
+		usb_kill_urb(ucs->urb_cmd_in);
+		dbg(DEBUG_INIT, "%s: command input URB unlinked", __func__);
+		usb_free_urb(ucs->urb_cmd_in);
+		ucs->urb_cmd_in = NULL;
+	}
+	if (ucs->urb_ctrl) {
+		usb_kill_urb(ucs->urb_ctrl);
+		dbg(DEBUG_INIT, "%s: control output URB unlinked", __func__);
+		usb_free_urb(ucs->urb_ctrl);
+		ucs->urb_ctrl = NULL;
+	}
+}
+
+/* gigaset_probe
+ * This function is called when a new USB device is connected.
+ * It checks whether the new device is handled by this driver.
+ */
+static int gigaset_probe(struct usb_interface *interface,
+			 const struct usb_device_id *id)
+{
+	struct usb_host_interface *hostif;
+	struct usb_device *udev = interface_to_usbdev(interface);
+	struct cardstate *cs = NULL;
+	struct bas_cardstate *ucs = NULL;
+	struct bas_bc_state *ubc;
+	struct usb_endpoint_descriptor *endpoint;
+	int i, j;
+	int ret;
+
+	IFNULLRETVAL(udev, -ENODEV);
+
+	dbg(DEBUG_ANY,
+	    "%s: Check if device matches .. (Vendor: 0x%x, Product: 0x%x)",
+	    __func__, le16_to_cpu(udev->descriptor.idVendor),
+	    le16_to_cpu(udev->descriptor.idProduct));
+
+	/* See if the device offered us matches what we can accept */
+	if ((le16_to_cpu(udev->descriptor.idVendor)  != USB_GIGA_VENDOR_ID) ||
+	    (le16_to_cpu(udev->descriptor.idProduct) != USB_GIGA_PRODUCT_ID &&
+	     le16_to_cpu(udev->descriptor.idProduct) != USB_4175_PRODUCT_ID &&
+	     le16_to_cpu(udev->descriptor.idProduct) != USB_SX303_PRODUCT_ID &&
+	     le16_to_cpu(udev->descriptor.idProduct) != USB_SX353_PRODUCT_ID)) {
+		dbg(DEBUG_ANY, "%s: unmatched ID - exiting", __func__);
+		return -ENODEV;
+	}
+
+	/* set required alternate setting */
+	hostif = interface->cur_altsetting;
+	if (hostif->desc.bAlternateSetting != 3) {
+		dbg(DEBUG_ANY,
+		    "%s: wrong alternate setting %d - trying to switch",
+		    __func__, hostif->desc.bAlternateSetting);
+		if (usb_set_interface(udev, hostif->desc.bInterfaceNumber, 3) < 0) {
+			warn("usb_set_interface failed, device %d interface %d altsetting %d",
+			     udev->devnum, hostif->desc.bInterfaceNumber,
+			     hostif->desc.bAlternateSetting);
+			return -ENODEV;
+		}
+		hostif = interface->cur_altsetting;
+	}
+
+	/* Reject application specific interfaces
+	 */
+	if (hostif->desc.bInterfaceClass != 255) {
+		warn("%s: bInterfaceClass == %d",
+		     __func__, hostif->desc.bInterfaceClass);
+		return -ENODEV;
+	}
+
+	info("%s: Device matched (Vendor: 0x%x, Product: 0x%x)",
+	     __func__, le16_to_cpu(udev->descriptor.idVendor),
+	     le16_to_cpu(udev->descriptor.idProduct));
+
+	cs = gigaset_getunassignedcs(driver);
+	if (!cs) {
+		err("%s: no free cardstate", __func__);
+		return -ENODEV;
+	}
+	ucs = cs->hw.bas;
+	ucs->udev = udev;
+	ucs->interface = interface;
+
+	/* allocate URBs:
+	 * - one for the interrupt pipe
+	 * - three for the different uses of the default control pipe
+	 * - three for each isochronous pipe
+	 */
+	ucs->urb_int_in = usb_alloc_urb(0, SLAB_KERNEL);
+	if (!ucs->urb_int_in) {
+		err("No free urbs available");
+		goto error;
+	}
+	ucs->urb_cmd_in = usb_alloc_urb(0, SLAB_KERNEL);
+	if (!ucs->urb_cmd_in) {
+		err("No free urbs available");
+		goto error;
+	}
+	ucs->urb_cmd_out = usb_alloc_urb(0, SLAB_KERNEL);
+	if (!ucs->urb_cmd_out) {
+		err("No free urbs available");
+		goto error;
+	}
+	ucs->urb_ctrl = usb_alloc_urb(0, SLAB_KERNEL);
+	if (!ucs->urb_ctrl) {
+		err("No free urbs available");
+		goto error;
+	}
+
+	for (j = 0; j < 2; ++j) {
+		ubc = cs->bcs[j].hw.bas;
+		for (i = 0; i < BAS_OUTURBS; ++i) {
+			ubc->isoouturbs[i].urb =
+				usb_alloc_urb(BAS_NUMFRAMES, SLAB_KERNEL);
+			if (!ubc->isoouturbs[i].urb) {
+				err("No free urbs available");
+				goto error;
+			}
+		}
+		for (i = 0; i < BAS_INURBS; ++i) {
+			ubc->isoinurbs[i] =
+				usb_alloc_urb(BAS_NUMFRAMES, SLAB_KERNEL);
+			if (!ubc->isoinurbs[i]) {
+				err("No free urbs available");
+				goto error;
+			}
+		}
+	}
+
+	ucs->rcvbuf = NULL;
+	ucs->rcvbuf_size = 0;
+
+	/* Fill the interrupt urb and send it to the core */
+	endpoint = &hostif->endpoint[0].desc;
+	usb_fill_int_urb(ucs->urb_int_in, udev,
+	                 usb_rcvintpipe(udev,
+	                                (endpoint->bEndpointAddress) & 0x0f),
+	                 ucs->int_in_buf, 3, read_int_callback, cs,
+	                 endpoint->bInterval);
+	ret = usb_submit_urb(ucs->urb_int_in, SLAB_KERNEL);
+	if (ret) {
+		err("could not submit interrupt URB: %s", get_usb_statmsg(ret));
+		goto error;
+	}
+
+	/* tell the device that the driver is ready */
+	if ((ret = req_submit(cs->bcs, HD_DEVICE_INIT_ACK, 0, 0)) != 0)
+		goto error;
+
+	/* tell common part that the device is ready */
+	if (startmode == SM_LOCKED)
+		atomic_set(&cs->mstate, MS_LOCKED);
+	if (!gigaset_start(cs))
+		goto error;
+
+	/* save address of controller structure */
+	usb_set_intfdata(interface, cs);
+
+	/* set up device sysfs */
+	gigaset_init_dev_sysfs(interface);
+	return 0;
+
+error:
+	freeurbs(cs);
+	gigaset_unassign(cs);
+	return -ENODEV;
+}
+
+/* gigaset_disconnect
+ * This function is called when the Gigaset base is unplugged.
+ */
+static void gigaset_disconnect(struct usb_interface *interface)
+{
+	struct cardstate *cs;
+	struct bas_cardstate *ucs;
+
+	/* clear device sysfs */
+	gigaset_free_dev_sysfs(interface);
+
+	cs = usb_get_intfdata(interface);
+	usb_set_intfdata(interface, NULL);
+
+	IFNULLRET(cs);
+	ucs = cs->hw.bas;
+	IFNULLRET(ucs);
+
+	info("disconnecting GigaSet base");
+	gigaset_stop(cs);
+	freeurbs(cs);
+	kfree(ucs->rcvbuf);
+	ucs->rcvbuf = NULL;
+	ucs->rcvbuf_size = 0;
+	atomic_set(&ucs->basstate, 0);
+	gigaset_unassign(cs);
+}
+
+static struct gigaset_ops gigops = {
+	gigaset_write_cmd,
+	gigaset_write_room,
+	gigaset_chars_in_buffer,
+	gigaset_brkchars,
+	gigaset_init_bchannel,
+	gigaset_close_bchannel,
+	gigaset_initbcshw,
+	gigaset_freebcshw,
+	gigaset_reinitbcshw,
+	gigaset_initcshw,
+	gigaset_freecshw,
+	gigaset_set_modem_ctrl,
+	gigaset_baud_rate,
+	gigaset_set_line_ctrl,
+	gigaset_isoc_send_skb,
+	gigaset_isoc_input,
+};
+
+/* bas_gigaset_init
+ * This function is called after the kernel module is loaded.
+ */
+static int __init bas_gigaset_init(void)
+{
+	int result;
+
+	/* allocate memory for our driver state and intialize it */
+	if ((driver = gigaset_initdriver(GIGASET_MINOR, GIGASET_MINORS,
+	                               GIGASET_MODULENAME, GIGASET_DEVNAME,
+	                               GIGASET_DEVFSNAME, &gigops,
+	                               THIS_MODULE)) == NULL)
+		goto error;
+
+	/* allocate memory for our device state and intialize it */
+	cardstate = gigaset_initcs(driver, 2, 0, 0, cidmode, GIGASET_MODULENAME);
+	if (!cardstate)
+		goto error;
+
+	/* register this driver with the USB subsystem */
+	result = usb_register(&gigaset_usb_driver);
+	if (result < 0) {
+		err("usb_register failed (error %d)", -result);
+		goto error;
+	}
+
+	info(DRIVER_AUTHOR);
+	info(DRIVER_DESC);
+	return 0;
+
+error:	if (cardstate)
+		gigaset_freecs(cardstate);
+	cardstate = NULL;
+	if (driver)
+		gigaset_freedriver(driver);
+	driver = NULL;
+	return -1;
+}
+
+/* bas_gigaset_exit
+ * This function is called before the kernel module is unloaded.
+ */
+static void __exit bas_gigaset_exit(void)
+{
+	gigaset_blockdriver(driver); /* => probe will fail
+	                              * => no gigaset_start any more
+	                              */
+
+	gigaset_shutdown(cardstate);
+	/* from now on, no isdn callback should be possible */
+
+	if (atomic_read(&cardstate->hw.bas->basstate) & BS_ATOPEN) {
+		dbg(DEBUG_ANY, "closing AT channel");
+		if (req_submit(cardstate->bcs,
+		               HD_CLOSE_ATCHANNEL, 0, BAS_TIMEOUT) >= 0) {
+			/* successfully submitted - wait for completion */
+			//wait_event_interruptible(cs->initwait, !cs->hw.bas->pending);
+			//FIXME need own wait queue? wakeup?
+		}
+	}
+
+	/* deregister this driver with the USB subsystem */
+	usb_deregister(&gigaset_usb_driver);
+	/* this will call the disconnect-callback */
+	/* from now on, no disconnect/probe callback should be running */
+
+	gigaset_freecs(cardstate);
+	cardstate = NULL;
+	gigaset_freedriver(driver);
+	driver = NULL;
+}
+
+
+module_init(bas_gigaset_init);
+module_exit(bas_gigaset_exit);
+
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");