/*
 * Stuff used by all variants of the driver
 *
 * Copyright (c) 2001 by Stefan Eilers,
 *                       Hansjoerg Lipp <hjlipp@web.de>,
 *                       Tilman Schmidt <tilman@imap.cc>.
 *
 * =====================================================================
 *      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.
 * =====================================================================
 */

#include "gigaset.h"
#include <linux/isdnif.h>
#include <linux/export.h>

#define SBUFSIZE        4096    /* sk_buff payload size */
#define TRANSBUFSIZE    768     /* bytes per skb for transparent receive */
#define HW_HDR_LEN      2       /* Header size used to store ack info */
#define MAX_BUF_SIZE    (SBUFSIZE - HW_HDR_LEN) /* max data packet from LL */

/* == Handling of I4L IO =====================================================*/

/* writebuf_from_LL
 * called by LL to transmit data on an open channel
 * inserts the buffer data into the send queue and starts the transmission
 * Note that this operation must not sleep!
 * When the buffer is processed completely, gigaset_skb_sent() should be called.
 * parameters:
 *      driverID        driver ID as assigned by LL
 *      channel         channel number
 *      ack             if != 0 LL wants to be notified on completion via
 *                      statcallb(ISDN_STAT_BSENT)
 *      skb             skb containing data to send
 * return value:
 *      number of accepted bytes
 *      0 if temporarily unable to accept data (out of buffer space)
 *      <0 on error (eg. -EINVAL)
 */
static int writebuf_from_LL(int driverID, int channel, int ack,
                            struct sk_buff *skb)
{
        struct cardstate *cs = gigaset_get_cs_by_id(driverID);
        struct bc_state *bcs;
        unsigned char *ack_header;
        unsigned len;

        if (!cs) {
                pr_err("%s: invalid driver ID (%d)\n", __func__, driverID);
                return -ENODEV;
        }
        if (channel < 0 || channel >= cs->channels) {
                dev_err(cs->dev, "%s: invalid channel ID (%d)\n",
                        __func__, channel);
                return -ENODEV;
        }
        bcs = &cs->bcs[channel];

        /* can only handle linear sk_buffs */
        if (skb_linearize(skb) < 0) {
                dev_err(cs->dev, "%s: skb_linearize failed\n", __func__);
                return -ENOMEM;
        }
        len = skb->len;

        gig_dbg(DEBUG_LLDATA,
                "Receiving data from LL (id: %d, ch: %d, ack: %d, sz: %d)",
                driverID, channel, ack, len);

        if (!len) {
                if (ack)
                        dev_notice(cs->dev, "%s: not ACKing empty packet\n",
                                   __func__);
                return 0;
        }
        if (len > MAX_BUF_SIZE) {
                dev_err(cs->dev, "%s: packet too large (%d bytes)\n",
                        __func__, len);
                return -EINVAL;
        }

        /* set up acknowledgement header */
        if (skb_headroom(skb) < HW_HDR_LEN) {
                /* should never happen */
                dev_err(cs->dev, "%s: insufficient skb headroom\n", __func__);
                return -ENOMEM;
        }
        skb_set_mac_header(skb, -HW_HDR_LEN);
        skb->mac_len = HW_HDR_LEN;
        ack_header = skb_mac_header(skb);
        if (ack) {
                ack_header[0] = len & 0xff;
                ack_header[1] = len >> 8;
        } else {
                ack_header[0] = ack_header[1] = 0;
        }
        gig_dbg(DEBUG_MCMD, "skb: len=%u, ack=%d: %02x %02x",
                len, ack, ack_header[0], ack_header[1]);

        /* pass to device-specific module */
        return cs->ops->send_skb(bcs, skb);
}

/**
 * gigaset_skb_sent() - acknowledge sending an skb
 * @bcs:        B channel descriptor structure.
 * @skb:        sent data.
 *
 * Called by hardware module {bas,ser,usb}_gigaset when the data in a
 * skb has been successfully sent, for signalling completion to the LL.
 */
void gigaset_skb_sent(struct bc_state *bcs, struct sk_buff *skb)
{
        isdn_if *iif = bcs->cs->iif;
        unsigned char *ack_header = skb_mac_header(skb);
        unsigned len;
        isdn_ctrl response;

        ++bcs->trans_up;

        if (skb->len)
                dev_warn(bcs->cs->dev, "%s: skb->len==%d\n",
                         __func__, skb->len);

        len = ack_header[0] + ((unsigned) ack_header[1] << 8);
        if (len) {
                gig_dbg(DEBUG_MCMD, "ACKing to LL (id: %d, ch: %d, sz: %u)",
                        bcs->cs->myid, bcs->channel, len);

                response.driver = bcs->cs->myid;
                response.command = ISDN_STAT_BSENT;
                response.arg = bcs->channel;
                response.parm.length = len;
                iif->statcallb(&response);
        }
}
EXPORT_SYMBOL_GPL(gigaset_skb_sent);

/**
 * gigaset_skb_rcvd() - pass received skb to LL
 * @bcs:        B channel descriptor structure.
 * @skb:        received data.
 *
 * Called by hardware module {bas,ser,usb}_gigaset when user data has
 * been successfully received, for passing to the LL.
 * Warning: skb must not be accessed anymore!
 */
void gigaset_skb_rcvd(struct bc_state *bcs, struct sk_buff *skb)
{
        isdn_if *iif = bcs->cs->iif;

        iif->rcvcallb_skb(bcs->cs->myid, bcs->channel, skb);
        bcs->trans_down++;
}
EXPORT_SYMBOL_GPL(gigaset_skb_rcvd);

/**
 * gigaset_isdn_rcv_err() - signal receive error
 * @bcs:        B channel descriptor structure.
 *
 * Called by hardware module {bas,ser,usb}_gigaset when a receive error
 * has occurred, for signalling to the LL.
 */
void gigaset_isdn_rcv_err(struct bc_state *bcs)
{
        isdn_if *iif = bcs->cs->iif;
        isdn_ctrl response;

        /* if currently ignoring packets, just count down */
        if (bcs->ignore) {
                bcs->ignore--;
                return;
        }

        /* update statistics */
        bcs->corrupted++;

        /* error -> LL */
        gig_dbg(DEBUG_CMD, "sending L1ERR");
        response.driver = bcs->cs->myid;
        response.command = ISDN_STAT_L1ERR;
        response.arg = bcs->channel;
        response.parm.errcode = ISDN_STAT_L1ERR_RECV;
        iif->statcallb(&response);
}
EXPORT_SYMBOL_GPL(gigaset_isdn_rcv_err);

/* This function will be called by LL to send commands
 * NOTE: LL ignores the returned value, for commands other than ISDN_CMD_IOCTL,
 * so don't put too much effort into it.
 */
static int command_from_LL(isdn_ctrl *cntrl)
{
        struct cardstate *cs;
        struct bc_state *bcs;
        int retval = 0;
        char **commands;
        int ch;
        int i;
        size_t l;

        gig_dbg(DEBUG_CMD, "driver: %d, command: %d, arg: 0x%lx",
                cntrl->driver, cntrl->command, cntrl->arg);

        cs = gigaset_get_cs_by_id(cntrl->driver);
        if (cs == NULL) {
                pr_err("%s: invalid driver ID (%d)\n", __func__, cntrl->driver);
                return -ENODEV;
        }
        ch = cntrl->arg & 0xff;

        switch (cntrl->command) {
        case ISDN_CMD_IOCTL:
                dev_warn(cs->dev, "ISDN_CMD_IOCTL not supported\n");
                return -EINVAL;

        case ISDN_CMD_DIAL:
                gig_dbg(DEBUG_CMD,
                        "ISDN_CMD_DIAL (phone: %s, msn: %s, si1: %d, si2: %d)",
                        cntrl->parm.setup.phone, cntrl->parm.setup.eazmsn,
                        cntrl->parm.setup.si1, cntrl->parm.setup.si2);

                if (ch >= cs->channels) {
                        dev_err(cs->dev,
                                "ISDN_CMD_DIAL: invalid channel (%d)\n", ch);
                        return -EINVAL;
                }
                bcs = cs->bcs + ch;
                if (gigaset_get_channel(bcs) < 0) {
                        dev_err(cs->dev, "ISDN_CMD_DIAL: channel not free\n");
                        return -EBUSY;
                }
                switch (bcs->proto2) {
                case L2_HDLC:
                        bcs->rx_bufsize = SBUFSIZE;
                        break;
                default:                        /* assume transparent */
                        bcs->rx_bufsize = TRANSBUFSIZE;
                }
                dev_kfree_skb(bcs->rx_skb);
                gigaset_new_rx_skb(bcs);

                commands = kzalloc(AT_NUM * (sizeof *commands), GFP_ATOMIC);
                if (!commands) {
                        gigaset_free_channel(bcs);
                        dev_err(cs->dev, "ISDN_CMD_DIAL: out of memory\n");
                        return -ENOMEM;
                }

                l = 3 + strlen(cntrl->parm.setup.phone);
                commands[AT_DIAL] = kmalloc(l, GFP_ATOMIC);
                if (!commands[AT_DIAL])
                        goto oom;
                if (cntrl->parm.setup.phone[0] == '*' &&
                    cntrl->parm.setup.phone[1] == '*') {
                        /* internal call: translate ** prefix to CTP value */
                        commands[AT_TYPE] = kstrdup("^SCTP=0\r", GFP_ATOMIC);
                        if (!commands[AT_TYPE])
                                goto oom;
                        snprintf(commands[AT_DIAL], l,
                                 "D%s\r", cntrl->parm.setup.phone + 2);
                } else {
                        commands[AT_TYPE] = kstrdup("^SCTP=1\r", GFP_ATOMIC);
                        if (!commands[AT_TYPE])
                                goto oom;
                        snprintf(commands[AT_DIAL], l,
                                 "D%s\r", cntrl->parm.setup.phone);
                }

                l = strlen(cntrl->parm.setup.eazmsn);
                if (l) {
                        l += 8;
                        commands[AT_MSN] = kmalloc(l, GFP_ATOMIC);
                        if (!commands[AT_MSN])
                                goto oom;
                        snprintf(commands[AT_MSN], l, "^SMSN=%s\r",
                                 cntrl->parm.setup.eazmsn);
                }

                switch (cntrl->parm.setup.si1) {
                case 1:         /* audio */
                        /* BC = 9090A3: 3.1 kHz audio, A-law */
                        commands[AT_BC] = kstrdup("^SBC=9090A3\r", GFP_ATOMIC);
                        if (!commands[AT_BC])
                                goto oom;
                        break;
                case 7:         /* data */
                default:        /* hope the app knows what it is doing */
                        /* BC = 8890: unrestricted digital information */
                        commands[AT_BC] = kstrdup("^SBC=8890\r", GFP_ATOMIC);
                        if (!commands[AT_BC])
                                goto oom;
                }
                /* ToDo: other si1 values, inspect si2, set HLC/LLC */

                commands[AT_PROTO] = kmalloc(9, GFP_ATOMIC);
                if (!commands[AT_PROTO])
                        goto oom;
                snprintf(commands[AT_PROTO], 9, "^SBPR=%u\r", bcs->proto2);

                commands[AT_ISO] = kmalloc(9, GFP_ATOMIC);
                if (!commands[AT_ISO])
                        goto oom;
                snprintf(commands[AT_ISO], 9, "^SISO=%u\r",
                         (unsigned) bcs->channel + 1);

                if (!gigaset_add_event(cs, &bcs->at_state, EV_DIAL, commands,
                                       bcs->at_state.seq_index, NULL)) {
                        for (i = 0; i < AT_NUM; ++i)
                                kfree(commands[i]);
                        kfree(commands);
                        gigaset_free_channel(bcs);
                        return -ENOMEM;
                }
                gigaset_schedule_event(cs);
                break;
        case ISDN_CMD_ACCEPTD:
                gig_dbg(DEBUG_CMD, "ISDN_CMD_ACCEPTD");
                if (ch >= cs->channels) {
                        dev_err(cs->dev,
                                "ISDN_CMD_ACCEPTD: invalid channel (%d)\n", ch);
                        return -EINVAL;
                }
                bcs = cs->bcs + ch;
                switch (bcs->proto2) {
                case L2_HDLC:
                        bcs->rx_bufsize = SBUFSIZE;
                        break;
                default:                        /* assume transparent */
                        bcs->rx_bufsize = TRANSBUFSIZE;
                }
                dev_kfree_skb(bcs->rx_skb);
                gigaset_new_rx_skb(bcs);
                if (!gigaset_add_event(cs, &bcs->at_state,
                                       EV_ACCEPT, NULL, 0, NULL))
                        return -ENOMEM;
                gigaset_schedule_event(cs);

                break;
        case ISDN_CMD_HANGUP:
                gig_dbg(DEBUG_CMD, "ISDN_CMD_HANGUP");
                if (ch >= cs->channels) {
                        dev_err(cs->dev,
                                "ISDN_CMD_HANGUP: invalid channel (%d)\n", ch);
                        return -EINVAL;
                }
                bcs = cs->bcs + ch;
                if (!gigaset_add_event(cs, &bcs->at_state,
                                       EV_HUP, NULL, 0, NULL))
                        return -ENOMEM;
                gigaset_schedule_event(cs);

                break;
        case ISDN_CMD_CLREAZ: /* Do not signal incoming signals */
                dev_info(cs->dev, "ignoring ISDN_CMD_CLREAZ\n");
                break;
        case ISDN_CMD_SETEAZ: /* Signal incoming calls for given MSN */
                dev_info(cs->dev, "ignoring ISDN_CMD_SETEAZ (%s)\n",
                         cntrl->parm.num);
                break;
        case ISDN_CMD_SETL2: /* Set L2 to given protocol */
                if (ch >= cs->channels) {
                        dev_err(cs->dev,
                                "ISDN_CMD_SETL2: invalid channel (%d)\n", ch);
                        return -EINVAL;
                }
                bcs = cs->bcs + ch;
                if (bcs->chstate & CHS_D_UP) {
                        dev_err(cs->dev,
                                "ISDN_CMD_SETL2: channel active (%d)\n", ch);
                        return -EINVAL;
                }
                switch (cntrl->arg >> 8) {
                case ISDN_PROTO_L2_HDLC:
                        gig_dbg(DEBUG_CMD, "ISDN_CMD_SETL2: setting L2_HDLC");
                        bcs->proto2 = L2_HDLC;
                        break;
                case ISDN_PROTO_L2_TRANS:
                        gig_dbg(DEBUG_CMD, "ISDN_CMD_SETL2: setting L2_VOICE");
                        bcs->proto2 = L2_VOICE;
                        break;
                default:
                        dev_err(cs->dev,
                                "ISDN_CMD_SETL2: unsupported protocol (%lu)\n",
                                cntrl->arg >> 8);
                        return -EINVAL;
                }
                break;
        case ISDN_CMD_SETL3: /* Set L3 to given protocol */
                gig_dbg(DEBUG_CMD, "ISDN_CMD_SETL3");
                if (ch >= cs->channels) {
                        dev_err(cs->dev,
                                "ISDN_CMD_SETL3: invalid channel (%d)\n", ch);
                        return -EINVAL;
                }

                if (cntrl->arg >> 8 != ISDN_PROTO_L3_TRANS) {
                        dev_err(cs->dev,
                                "ISDN_CMD_SETL3: unsupported protocol (%lu)\n",
                                cntrl->arg >> 8);
                        return -EINVAL;
                }

                break;

        default:
                gig_dbg(DEBUG_CMD, "unknown command %d from LL",
                        cntrl->command);
                return -EINVAL;
        }

        return retval;

oom:
        dev_err(bcs->cs->dev, "out of memory\n");
        for (i = 0; i < AT_NUM; ++i)
                kfree(commands[i]);
        kfree(commands);
        gigaset_free_channel(bcs);
        return -ENOMEM;
}

static void gigaset_i4l_cmd(struct cardstate *cs, int cmd)
{
        isdn_if *iif = cs->iif;
        isdn_ctrl command;

        command.driver = cs->myid;
        command.command = cmd;
        command.arg = 0;
        iif->statcallb(&command);
}

static void gigaset_i4l_channel_cmd(struct bc_state *bcs, int cmd)
{
        isdn_if *iif = bcs->cs->iif;
        isdn_ctrl command;

        command.driver = bcs->cs->myid;
        command.command = cmd;
        command.arg = bcs->channel;
        iif->statcallb(&command);
}

/**
 * gigaset_isdn_icall() - signal incoming call
 * @at_state:   connection state structure.
 *
 * Called by main module to notify the LL that an incoming call has been
 * received. @at_state contains the parameters of the call.
 *
 * Return value: call disposition (ICALL_*)
 */
int gigaset_isdn_icall(struct at_state_t *at_state)
{
        struct cardstate *cs = at_state->cs;
        struct bc_state *bcs = at_state->bcs;
        isdn_if *iif = cs->iif;
        isdn_ctrl response;
        int retval;

        /* fill ICALL structure */
        response.parm.setup.si1 = 0;    /* default: unknown */
        response.parm.setup.si2 = 0;
        response.parm.setup.screen = 0;
        response.parm.setup.plan = 0;
        if (!at_state->str_var[STR_ZBC]) {
                /* no BC (internal call): assume speech, A-law */
                response.parm.setup.si1 = 1;
        } else if (!strcmp(at_state->str_var[STR_ZBC], "8890")) {
                /* unrestricted digital information */
                response.parm.setup.si1 = 7;
        } else if (!strcmp(at_state->str_var[STR_ZBC], "8090A3")) {
                /* speech, A-law */
                response.parm.setup.si1 = 1;
        } else if (!strcmp(at_state->str_var[STR_ZBC], "9090A3")) {
                /* 3,1 kHz audio, A-law */
                response.parm.setup.si1 = 1;
                response.parm.setup.si2 = 2;
        } else {
                dev_warn(cs->dev, "RING ignored - unsupported BC %s\n",
                         at_state->str_var[STR_ZBC]);
                return ICALL_IGNORE;
        }
        if (at_state->str_var[STR_NMBR]) {
                strlcpy(response.parm.setup.phone, at_state->str_var[STR_NMBR],
                        sizeof response.parm.setup.phone);
        } else
                response.parm.setup.phone[0] = 0;
        if (at_state->str_var[STR_ZCPN]) {
                strlcpy(response.parm.setup.eazmsn, at_state->str_var[STR_ZCPN],
                        sizeof response.parm.setup.eazmsn);
        } else
                response.parm.setup.eazmsn[0] = 0;

        if (!bcs) {
                dev_notice(cs->dev, "no channel for incoming call\n");
                response.command = ISDN_STAT_ICALLW;
                response.arg = 0;
        } else {
                gig_dbg(DEBUG_CMD, "Sending ICALL");
                response.command = ISDN_STAT_ICALL;
                response.arg = bcs->channel;
        }
        response.driver = cs->myid;
        retval = iif->statcallb(&response);
        gig_dbg(DEBUG_CMD, "Response: %d", retval);
        switch (retval) {
        case 0: /* no takers */
                return ICALL_IGNORE;
        case 1: /* alerting */
                bcs->chstate |= CHS_NOTIFY_LL;
                return ICALL_ACCEPT;
        case 2: /* reject */
                return ICALL_REJECT;
        case 3: /* incomplete */
                dev_warn(cs->dev,
                         "LL requested unsupported feature: Incomplete Number\n");
                return ICALL_IGNORE;
        case 4: /* proceeding */
                /* Gigaset will send ALERTING anyway.
                 * There doesn't seem to be a way to avoid this.
                 */
                return ICALL_ACCEPT;
        case 5: /* deflect */
                dev_warn(cs->dev,
                         "LL requested unsupported feature: Call Deflection\n");
                return ICALL_IGNORE;
        default:
                dev_err(cs->dev, "LL error %d on ICALL\n", retval);
                return ICALL_IGNORE;
        }
}

/**
 * gigaset_isdn_connD() - signal D channel connect
 * @bcs:        B channel descriptor structure.
 *
 * Called by main module to notify the LL that the D channel connection has
 * been established.
 */
void gigaset_isdn_connD(struct bc_state *bcs)
{
        gig_dbg(DEBUG_CMD, "sending DCONN");
        gigaset_i4l_channel_cmd(bcs, ISDN_STAT_DCONN);
}

/**
 * gigaset_isdn_hupD() - signal D channel hangup
 * @bcs:        B channel descriptor structure.
 *
 * Called by main module to notify the LL that the D channel connection has
 * been shut down.
 */
void gigaset_isdn_hupD(struct bc_state *bcs)
{
        gig_dbg(DEBUG_CMD, "sending DHUP");
        gigaset_i4l_channel_cmd(bcs, ISDN_STAT_DHUP);
}

/**
 * gigaset_isdn_connB() - signal B channel connect
 * @bcs:        B channel descriptor structure.
 *
 * Called by main module to notify the LL that the B channel connection has
 * been established.
 */
void gigaset_isdn_connB(struct bc_state *bcs)
{
        gig_dbg(DEBUG_CMD, "sending BCONN");
        gigaset_i4l_channel_cmd(bcs, ISDN_STAT_BCONN);
}

/**
 * gigaset_isdn_hupB() - signal B channel hangup
 * @bcs:        B channel descriptor structure.
 *
 * Called by main module to notify the LL that the B channel connection has
 * been shut down.
 */
void gigaset_isdn_hupB(struct bc_state *bcs)
{
        gig_dbg(DEBUG_CMD, "sending BHUP");
        gigaset_i4l_channel_cmd(bcs, ISDN_STAT_BHUP);
}

/**
 * gigaset_isdn_start() - signal device availability
 * @cs:         device descriptor structure.
 *
 * Called by main module to notify the LL that the device is available for
 * use.
 */
void gigaset_isdn_start(struct cardstate *cs)
{
        gig_dbg(DEBUG_CMD, "sending RUN");
        gigaset_i4l_cmd(cs, ISDN_STAT_RUN);
}

/**
 * gigaset_isdn_stop() - signal device unavailability
 * @cs:         device descriptor structure.
 *
 * Called by main module to notify the LL that the device is no longer
 * available for use.
 */
void gigaset_isdn_stop(struct cardstate *cs)
{
        gig_dbg(DEBUG_CMD, "sending STOP");
        gigaset_i4l_cmd(cs, ISDN_STAT_STOP);
}

/**
 * gigaset_isdn_regdev() - register to LL
 * @cs:         device descriptor structure.
 * @isdnid:     device name.
 *
 * Return value: 0 on success, error code < 0 on failure
 */
int gigaset_isdn_regdev(struct cardstate *cs, const char *isdnid)
{
        isdn_if *iif;

        iif = kmalloc(sizeof *iif, GFP_KERNEL);
        if (!iif) {
                pr_err("out of memory\n");
                return -ENOMEM;
        }

        if (snprintf(iif->id, sizeof iif->id, "%s_%u", isdnid, cs->minor_index)
            >= sizeof iif->id) {
                pr_err("ID too long: %s\n", isdnid);
                kfree(iif);
                return -EINVAL;
        }

        iif->owner = THIS_MODULE;
        iif->channels = cs->channels;
        iif->maxbufsize = MAX_BUF_SIZE;
        iif->features = ISDN_FEATURE_L2_TRANS |
                ISDN_FEATURE_L2_HDLC |
                ISDN_FEATURE_L2_X75I |
                ISDN_FEATURE_L3_TRANS |
                ISDN_FEATURE_P_EURO;
        iif->hl_hdrlen = HW_HDR_LEN;            /* Area for storing ack */
        iif->command = command_from_LL;
        iif->writebuf_skb = writebuf_from_LL;
        iif->writecmd = NULL;                   /* Don't support isdnctrl */
        iif->readstat = NULL;                   /* Don't support isdnctrl */
        iif->rcvcallb_skb = NULL;               /* Will be set by LL */
        iif->statcallb = NULL;                  /* Will be set by LL */

        if (!register_isdn(iif)) {
                pr_err("register_isdn failed\n");
                kfree(iif);
                return -EINVAL;
        }

        cs->iif = iif;
        cs->myid = iif->channels;               /* Set my device id */
        cs->hw_hdr_len = HW_HDR_LEN;
        return 0;
}

/**
 * gigaset_isdn_unregdev() - unregister device from LL
 * @cs:         device descriptor structure.
 */
void gigaset_isdn_unregdev(struct cardstate *cs)
{
        gig_dbg(DEBUG_CMD, "sending UNLOAD");
        gigaset_i4l_cmd(cs, ISDN_STAT_UNLOAD);
        kfree(cs->iif);
        cs->iif = NULL;
}

/**
 * gigaset_isdn_regdrv() - register driver to LL
 */
void gigaset_isdn_regdrv(void)
{
        pr_info("ISDN4Linux interface\n");
        /* nothing to do */
}

/**
 * gigaset_isdn_unregdrv() - unregister driver from LL
 */
void gigaset_isdn_unregdrv(void)
{
        /* nothing to do */
}