text: /* $Id: isdnif.h,v 1.37.6.6 2001/09/23 22:25:05 kai Exp $
   *
   * Linux ISDN subsystem
   * Definition of the interface between the subsystem and its low-level drivers.
   *
   * Copyright 1994,95,96 by Fritz Elfert (fritz@isdn4linux.de)
   * Copyright 1995,96    Thinking Objects Software GmbH Wuerzburg
   * 
   * This software may be used and distributed according to the terms
   * of the GNU General Public License, incorporated herein by reference.
   *
   */
  
  #ifndef __ISDNIF_H__
  #define __ISDNIF_H__
  
  
  /*
   * Values for general protocol-selection
   */
  #define ISDN_PTYPE_UNKNOWN   0   /* Protocol undefined   */
  #define ISDN_PTYPE_1TR6      1   /* german 1TR6-protocol */
  #define ISDN_PTYPE_EURO      2   /* EDSS1-protocol       */
  #define ISDN_PTYPE_LEASED    3   /* for leased lines     */
  #define ISDN_PTYPE_NI1       4   /* US NI-1 protocol     */
  #define ISDN_PTYPE_MAX       7   /* Max. 8 Protocols     */
  
  /*
   * Values for Layer-2-protocol-selection
   */
  #define ISDN_PROTO_L2_X75I   0   /* X75/LAPB with I-Frames            */
  #define ISDN_PROTO_L2_X75UI  1   /* X75/LAPB with UI-Frames           */
  #define ISDN_PROTO_L2_X75BUI 2   /* X75/LAPB with UI-Frames           */
  #define ISDN_PROTO_L2_HDLC   3   /* HDLC                              */
  #define ISDN_PROTO_L2_TRANS  4   /* Transparent (Voice)               */
  #define ISDN_PROTO_L2_X25DTE 5   /* X25/LAPB DTE mode                 */
  #define ISDN_PROTO_L2_X25DCE 6   /* X25/LAPB DCE mode                 */
  #define ISDN_PROTO_L2_V11096 7   /* V.110 bitrate adaption 9600 Baud  */
  #define ISDN_PROTO_L2_V11019 8   /* V.110 bitrate adaption 19200 Baud */
  #define ISDN_PROTO_L2_V11038 9   /* V.110 bitrate adaption 38400 Baud */
  #define ISDN_PROTO_L2_MODEM  10  /* Analog Modem on Board */
  #define ISDN_PROTO_L2_FAX    11  /* Fax Group 2/3         */
  #define ISDN_PROTO_L2_HDLC_56K 12   /* HDLC 56k                          */
  #define ISDN_PROTO_L2_MAX    15  /* Max. 16 Protocols                 */
  
  /*
   * Values for Layer-3-protocol-selection
   */
  #define ISDN_PROTO_L3_TRANS	0	/* Transparent */
  #define ISDN_PROTO_L3_TRANSDSP	1	/* Transparent with DSP */
  #define ISDN_PROTO_L3_FCLASS2	2	/* Fax Group 2/3 CLASS 2 */
  #define ISDN_PROTO_L3_FCLASS1	3	/* Fax Group 2/3 CLASS 1 */
  #define ISDN_PROTO_L3_MAX	7	/* Max. 8 Protocols */
  
  #ifdef __KERNEL__
  
  #include <linux/config.h>
  #include <linux/skbuff.h>
  
  /***************************************************************************/
  /* Extensions made by Werner Cornelius (werner@ikt.de)                     */
  /*                                                                         */ 
  /* The proceed command holds a incoming call in a state to leave processes */
  /* enough time to check whether ist should be accepted.                    */
  /* The PROT_IO Command extends the interface to make protocol dependent    */
  /* features available (call diversion, call waiting...).                   */
  /*                                                                         */ 
  /* The PROT_IO Command is executed with the desired driver id and the arg  */
  /* parameter coded as follows:                                             */
  /* The lower 8 bits of arg contain the desired protocol from ISDN_PTYPE    */
  /* definitions. The upper 24 bits represent the protocol specific cmd/stat.*/
  /* Any additional data is protocol and command specific.                   */
  /* This mechanism also applies to the statcallb callback STAT_PROT.        */    
  /*                                                                         */
  /* This suggested extension permits an easy expansion of protocol specific */
  /* handling. Extensions may be added at any time without changing the HL   */
  /* driver code and not getting conflicts without certifications.           */
  /* The well known CAPI 2.0 interface handles such extensions in a similar  */
  /* way. Perhaps a protocol specific module may be added and separately     */
  /* loaded and linked to the basic isdn module for handling.                */                    
  /***************************************************************************/
  
  /*****************/
  /* DSS1 commands */ 
  /*****************/
  #define DSS1_CMD_INVOKE       ((0x00 << 8) | ISDN_PTYPE_EURO)   /* invoke a supplementary service */
  #define DSS1_CMD_INVOKE_ABORT ((0x01 << 8) | ISDN_PTYPE_EURO)   /* abort a invoke cmd */
  
  /*******************************/
  /* DSS1 Status callback values */
  /*******************************/
  #define DSS1_STAT_INVOKE_RES  ((0x80 << 8) | ISDN_PTYPE_EURO)   /* Result for invocation */
  #define DSS1_STAT_INVOKE_ERR  ((0x81 << 8) | ISDN_PTYPE_EURO)   /* Error Return for invocation */
  #define DSS1_STAT_INVOKE_BRD  ((0x82 << 8) | ISDN_PTYPE_EURO)   /* Deliver invoke broadcast info */
  
  
  /*********************************************************************/
  /* structures for DSS1 commands and callback                         */
  /*                                                                   */
  /* An action is invoked by sending a DSS1_CMD_INVOKE. The ll_id, proc*/
  /* timeout, datalen and data fields must be set before calling.      */
  /*                                                                   */
  /* The return value is a positive hl_id value also delivered in the  */
  /* hl_id field. A value of zero signals no more left hl_id capacitys.*/
  /* A negative return value signals errors in LL. So if the return    */
  /* value is <= 0 no action in LL will be taken -> request ignored    */
  /*                                                                   */
  /* The timeout field must be filled with a positive value specifying */
  /* the amount of time the INVOKED process waits for a reaction from  */
  /* the network.                                                      */
  /* If a response (either error or result) is received during this    */
  /* intervall, a reporting callback is initiated and the process will */
  /* be deleted, the hl identifier will be freed.                      */
  /* If no response is received during the specified intervall, a error*/
  /* callback is initiated with timeout set to -1 and a datalen set    */
  /* to 0.                                                             */
  /* If timeout is set to a value <= 0 during INVOCATION the process is*/
  /* immediately deleted after sending the data. No callback occurs !  */
  /*                                                                   */
  /* A currently waiting process may be aborted with INVOKE_ABORT. No  */
  /* callback will occur when a process has been aborted.              */
  /*                                                                   */
  /* Broadcast invoke frames from the network are reported via the     */
  /* STAT_INVOKE_BRD callback. The ll_id is set to 0, the other fields */
  /* are supplied by the network and not by the HL.                    */   
  /*********************************************************************/
  
  /*****************/
  /* NI1 commands */ 
  /*****************/
  #define NI1_CMD_INVOKE       ((0x00 << 8) | ISDN_PTYPE_NI1)   /* invoke a supplementary service */
  #define NI1_CMD_INVOKE_ABORT ((0x01 << 8) | ISDN_PTYPE_NI1)   /* abort a invoke cmd */
  
  /*******************************/
  /* NI1 Status callback values */
  /*******************************/
  #define NI1_STAT_INVOKE_RES  ((0x80 << 8) | ISDN_PTYPE_NI1)   /* Result for invocation */
  #define NI1_STAT_INVOKE_ERR  ((0x81 << 8) | ISDN_PTYPE_NI1)   /* Error Return for invocation */
  #define NI1_STAT_INVOKE_BRD  ((0x82 << 8) | ISDN_PTYPE_NI1)   /* Deliver invoke broadcast info */
  
  typedef struct
    { ulong ll_id; /* ID supplied by LL when executing    */
  		 /* a command and returned by HL for    */
                   /* INVOKE_RES and INVOKE_ERR           */
      int hl_id;   /* ID supplied by HL when called       */
                   /* for executing a cmd and delivered   */
                   /* for results and errors              */
                   /* must be supplied by LL when aborting*/  
      int proc;    /* invoke procedure used by CMD_INVOKE */
                   /* returned by callback and broadcast  */ 
      int timeout; /* timeout for INVOKE CMD in ms        */
                   /* -1  in stat callback when timed out */
                   /* error value when error callback     */
      int datalen; /* length of cmd or stat data          */
      u_char *data;/* pointer to data delivered or send   */
    } isdn_cmd_stat;
  
  /*
   * Commands from linklevel to lowlevel
   *
   */
  #define ISDN_CMD_IOCTL    0       /* Perform ioctl                         */
  #define ISDN_CMD_DIAL     1       /* Dial out                              */
  #define ISDN_CMD_ACCEPTD  2       /* Accept an incoming call on D-Chan.    */
  #define ISDN_CMD_ACCEPTB  3       /* Request B-Channel connect.            */
  #define ISDN_CMD_HANGUP   4       /* Hangup                                */
  #define ISDN_CMD_CLREAZ   5       /* Clear EAZ(s) of channel               */
  #define ISDN_CMD_SETEAZ   6       /* Set EAZ(s) of channel                 */
  #define ISDN_CMD_SETL2   10       /* Set B-Chan. Layer2-Parameter          */
  #define ISDN_CMD_SETL3   12       /* Set B-Chan. Layer3-Parameter          */
  #define ISDN_CMD_PROCEED 18       /* Proceed with call establishment       */
  #define ISDN_CMD_ALERT   19       /* Alert after Proceeding                */
  #define ISDN_CMD_REDIR   20       /* Redir a incoming call                 */
  #define ISDN_CMD_PROT_IO 21       /* Protocol specific commands            */
  #define CAPI_PUT_MESSAGE 22       /* CAPI message send down or up          */
  #define ISDN_CMD_FAXCMD  23       /* FAX commands to HL-driver             */
  #define ISDN_CMD_AUDIO   24       /* DSP, DTMF, ... settings               */
  
  /*
   * Status-Values delivered from lowlevel to linklevel via
   * statcallb().
   *
   */
  #define ISDN_STAT_STAVAIL 256    /* Raw status-data available             */
  #define ISDN_STAT_ICALL   257    /* Incoming call detected                */
  #define ISDN_STAT_RUN     258    /* Signal protocol-code is running       */
  #define ISDN_STAT_STOP    259    /* Signal halt of protocol-code          */
  #define ISDN_STAT_DCONN   260    /* Signal D-Channel connect              */
  #define ISDN_STAT_BCONN   261    /* Signal B-Channel connect              */
  #define ISDN_STAT_DHUP    262    /* Signal D-Channel disconnect           */
  #define ISDN_STAT_BHUP    263    /* Signal B-Channel disconnect           */
  #define ISDN_STAT_CINF    264    /* Charge-Info                           */
  #define ISDN_STAT_LOAD    265    /* Signal new lowlevel-driver is loaded  */
  #define ISDN_STAT_UNLOAD  266    /* Signal unload of lowlevel-driver      */
  #define ISDN_STAT_BSENT   267    /* Signal packet sent                    */
  #define ISDN_STAT_ADDCH   269    /* Add more Channels                     */
  #define ISDN_STAT_CAUSE   270    /* Cause-Message                         */
  #define ISDN_STAT_ICALLW  271    /* Incoming call without B-chan waiting  */
  #define ISDN_STAT_REDIR   272    /* Redir result                          */
  #define ISDN_STAT_PROT    273    /* protocol IO specific callback         */
  #define ISDN_STAT_DISPLAY 274    /* deliver a received display message    */
  #define ISDN_STAT_FAXIND  276    /* FAX indications from HL-driver        */
  #define ISDN_STAT_AUDIO   277    /* DTMF, DSP indications                 */
  #define ISDN_STAT_DISCH   278    /* Disable/Enable channel usage          */
  
  /*
   * Audio commands
   */
  #define ISDN_AUDIO_SETDD	0	/* Set DTMF detection           */
  #define ISDN_AUDIO_DTMF		1	/* Rx/Tx DTMF                   */
  
  /*
   * Values for feature-field of interface-struct.
   */
  /* Layer 2 */
  #define ISDN_FEATURE_L2_X75I    (0x0001 << ISDN_PROTO_L2_X75I)
  #define ISDN_FEATURE_L2_X75UI   (0x0001 << ISDN_PROTO_L2_X75UI)
  #define ISDN_FEATURE_L2_X75BUI  (0x0001 << ISDN_PROTO_L2_X75BUI)
  #define ISDN_FEATURE_L2_HDLC    (0x0001 << ISDN_PROTO_L2_HDLC)
  #define ISDN_FEATURE_L2_TRANS   (0x0001 << ISDN_PROTO_L2_TRANS)
  #define ISDN_FEATURE_L2_X25DTE  (0x0001 << ISDN_PROTO_L2_X25DTE)
  #define ISDN_FEATURE_L2_X25DCE  (0x0001 << ISDN_PROTO_L2_X25DCE)
  #define ISDN_FEATURE_L2_V11096  (0x0001 << ISDN_PROTO_L2_V11096)
  #define ISDN_FEATURE_L2_V11019  (0x0001 << ISDN_PROTO_L2_V11019)
  #define ISDN_FEATURE_L2_V11038  (0x0001 << ISDN_PROTO_L2_V11038)
  #define ISDN_FEATURE_L2_MODEM   (0x0001 << ISDN_PROTO_L2_MODEM)
  #define ISDN_FEATURE_L2_FAX	(0x0001 << ISDN_PROTO_L2_FAX)
  #define ISDN_FEATURE_L2_HDLC_56K (0x0001 << ISDN_PROTO_L2_HDLC_56K)
  
  #define ISDN_FEATURE_L2_MASK    (0x0FFFF) /* Max. 16 protocols */
  #define ISDN_FEATURE_L2_SHIFT   (0)
  
  /* Layer 3 */
  #define ISDN_FEATURE_L3_TRANS   (0x10000 << ISDN_PROTO_L3_TRANS)
  #define ISDN_FEATURE_L3_TRANSDSP (0x10000 << ISDN_PROTO_L3_TRANSDSP)
  #define ISDN_FEATURE_L3_FCLASS2	(0x10000 << ISDN_PROTO_L3_FCLASS2)
  #define ISDN_FEATURE_L3_FCLASS1	(0x10000 << ISDN_PROTO_L3_FCLASS1)
  
  #define ISDN_FEATURE_L3_MASK    (0x0FF0000) /* Max. 8 Protocols */
  #define ISDN_FEATURE_L3_SHIFT   (16)
  
  /* Signaling */
  #define ISDN_FEATURE_P_UNKNOWN  (0x1000000 << ISDN_PTYPE_UNKNOWN)
  #define ISDN_FEATURE_P_1TR6     (0x1000000 << ISDN_PTYPE_1TR6)
  #define ISDN_FEATURE_P_EURO     (0x1000000 << ISDN_PTYPE_EURO)
  #define ISDN_FEATURE_P_NI1      (0x1000000 << ISDN_PTYPE_NI1)
  
  #define ISDN_FEATURE_P_MASK     (0x0FF000000) /* Max. 8 Protocols */
  #define ISDN_FEATURE_P_SHIFT    (24)
  
  typedef struct setup_parm {
      unsigned char phone[32];	/* Remote Phone-Number */
      unsigned char eazmsn[32];	/* Local EAZ or MSN    */
      unsigned char si1;      /* Service Indicator 1 */
      unsigned char si2;      /* Service Indicator 2 */
      unsigned char plan;     /* Numbering plan      */
      unsigned char screen;   /* Screening info      */
  } setup_parm;
  
  
  /* T.30 Fax G3 */
  
  #define FAXIDLEN 21
  
  typedef struct T30_s {
  	/* session parameters */
  	__u8 resolution		__attribute__ ((packed));
  	__u8 rate		__attribute__ ((packed));
  	__u8 width		__attribute__ ((packed));
  	__u8 length		__attribute__ ((packed));
  	__u8 compression	__attribute__ ((packed));
  	__u8 ecm		__attribute__ ((packed));
  	__u8 binary		__attribute__ ((packed));
  	__u8 scantime		__attribute__ ((packed));
  	__u8 id[FAXIDLEN]	__attribute__ ((packed));
  	/* additional parameters */
  	__u8 phase		__attribute__ ((packed));
  	__u8 direction		__attribute__ ((packed));
  	__u8 code		__attribute__ ((packed));
  	__u8 badlin		__attribute__ ((packed));
  	__u8 badmul		__attribute__ ((packed));
  	__u8 bor		__attribute__ ((packed));
  	__u8 fet		__attribute__ ((packed));
  	__u8 pollid[FAXIDLEN]	__attribute__ ((packed));
  	__u8 cq			__attribute__ ((packed));
  	__u8 cr			__attribute__ ((packed));
  	__u8 ctcrty		__attribute__ ((packed));
  	__u8 minsp		__attribute__ ((packed));
  	__u8 phcto		__attribute__ ((packed));
  	__u8 rel		__attribute__ ((packed));
  	__u8 nbc		__attribute__ ((packed));
  	/* remote station parameters */
  	__u8 r_resolution	__attribute__ ((packed));
  	__u8 r_rate		__attribute__ ((packed));
  	__u8 r_width		__attribute__ ((packed));
  	__u8 r_length		__attribute__ ((packed));
  	__u8 r_compression	__attribute__ ((packed));
  	__u8 r_ecm		__attribute__ ((packed));
  	__u8 r_binary		__attribute__ ((packed));
  	__u8 r_scantime		__attribute__ ((packed));
  	__u8 r_id[FAXIDLEN]	__attribute__ ((packed));
  	__u8 r_code		__attribute__ ((packed));
  } T30_s;
  
  #define ISDN_TTY_FAX_CONN_IN	0
  #define ISDN_TTY_FAX_CONN_OUT	1
  
  #define ISDN_TTY_FAX_FCON	0
  #define ISDN_TTY_FAX_DIS 	1
  #define ISDN_TTY_FAX_FTT 	2
  #define ISDN_TTY_FAX_MCF 	3
  #define ISDN_TTY_FAX_DCS 	4
  #define ISDN_TTY_FAX_TRAIN_OK	5
  #define ISDN_TTY_FAX_EOP 	6
  #define ISDN_TTY_FAX_EOM 	7
  #define ISDN_TTY_FAX_MPS 	8
  #define ISDN_TTY_FAX_DTC 	9
  #define ISDN_TTY_FAX_RID 	10
  #define ISDN_TTY_FAX_HNG 	11
  #define ISDN_TTY_FAX_DT  	12
  #define ISDN_TTY_FAX_FCON_I	13
  #define ISDN_TTY_FAX_DR  	14
  #define ISDN_TTY_FAX_ET  	15
  #define ISDN_TTY_FAX_CFR 	16
  #define ISDN_TTY_FAX_PTS 	17
  #define ISDN_TTY_FAX_SENT	18
  
  #define ISDN_FAX_PHASE_IDLE	0
  #define ISDN_FAX_PHASE_A	1
  #define ISDN_FAX_PHASE_B   	2
  #define ISDN_FAX_PHASE_C   	3
  #define ISDN_FAX_PHASE_D   	4
  #define ISDN_FAX_PHASE_E   	5
  
  #define ISDN_FAX_CLASS1_FAE	0
  #define ISDN_FAX_CLASS1_FTS	1
  #define ISDN_FAX_CLASS1_FRS	2
  #define ISDN_FAX_CLASS1_FTM	3
  #define ISDN_FAX_CLASS1_FRM	4
  #define ISDN_FAX_CLASS1_FTH	5
  #define ISDN_FAX_CLASS1_FRH	6
  #define ISDN_FAX_CLASS1_CTRL	7
  
  #define ISDN_FAX_CLASS1_OK	0
  #define ISDN_FAX_CLASS1_CONNECT	1
  #define ISDN_FAX_CLASS1_NOCARR	2
  #define ISDN_FAX_CLASS1_ERROR	3
  #define ISDN_FAX_CLASS1_FCERROR	4
  #define ISDN_FAX_CLASS1_QUERY	5
  
  typedef struct {
  	__u8	cmd;
  	__u8	subcmd;
  	__u8	para[50];
  } aux_s;
  
  #define AT_COMMAND	0
  #define AT_EQ_VALUE	1
  #define AT_QUERY	2
  #define AT_EQ_QUERY	3
  
  /* CAPI structs */
  
  /* this is compatible to the old union size */
  #define MAX_CAPI_PARA_LEN 50
  
  typedef struct {
  	/* Header */
  	__u16 Length;
  	__u16 ApplId;
  	__u8 Command;
  	__u8 Subcommand;
  	__u16 Messagenumber;
  
  	/* Parameter */
  	union {
  		__u32 Controller;
  		__u32 PLCI;
  		__u32 NCCI;
  	} adr;
  	__u8 para[MAX_CAPI_PARA_LEN];
  } capi_msg;
  
  /*
   * Structure for exchanging above infos
   *
   */
  typedef struct {
  	int   driver;		/* Lowlevel-Driver-ID            */
  	int   command;		/* Command or Status (see above) */
  	ulong arg;		/* Additional Data               */
  	union {
  		ulong errcode;	/* Type of error with STAT_L1ERR	*/
  		int length;	/* Amount of bytes sent with STAT_BSENT	*/
  		u_char num[50];	/* Additional Data			*/
  		setup_parm setup;/* For SETUP msg			*/
  		capi_msg cmsg;	/* For CAPI like messages		*/
  		char display[85];/* display message data		*/ 
  		isdn_cmd_stat isdn_io; /* ISDN IO-parameter/result	*/
  		aux_s aux;	/* for modem commands/indications	*/
  		T30_s	*fax;	/* Pointer to ttys fax struct		*/
  		ulong userdata;	/* User Data */
  	} parm;
  } isdn_ctrl;
  
  #define dss1_io    isdn_io
  #define ni1_io     isdn_io
  
  /*
   * The interface-struct itself (initialized at load-time of lowlevel-driver)
   *
   * See Documentation/isdn/INTERFACE for a description, how the communication
   * between the ISDN subsystem and its drivers is done.
   *
   */
  typedef struct {
    struct module *owner;
  
    /* Number of channels supported by this driver
     */
    int channels;
  
    /* 
     * Maximum Size of transmit/receive-buffer this driver supports.
     */
    int maxbufsize;
  
    /* Feature-Flags for this driver.
     * See defines ISDN_FEATURE_... for Values
     */
    unsigned long features;
  
    /*
     * Needed for calculating
     * dev->hard_header_len = linklayer header + hl_hdrlen;
     * Drivers, not supporting sk_buff's should set this to 0.
     */
    unsigned short hl_hdrlen;
  
    /*
     * Receive-Callback using sk_buff's
     * Parameters:
     *             int                    Driver-ID
     *             int                    local channel-number (0 ...)
     *             struct sk_buff *skb    received Data
     */
    void (*rcvcallb_skb)(int, int, struct sk_buff *);
  
    /* Status-Callback
     * Parameters:
     *             isdn_ctrl*
     *                   driver  = Driver ID.
     *                   command = One of above ISDN_STAT_... constants.
     *                   arg     = depending on status-type.
     *                   num     = depending on status-type.
     */
    int (*statcallb)(isdn_ctrl*);
  
    /* Send command
     * Parameters:
     *             isdn_ctrl*
     *                   driver  = Driver ID.
     *                   command = One of above ISDN_CMD_... constants.
     *                   arg     = depending on command.
     *                   num     = depending on command.
     */
    int (*command)(isdn_ctrl*);
  
    /*
     * Send data using sk_buff's
     * Parameters:
     *             int                    driverId
     *             int                    local channel-number (0...)
     *             int                    Flag: Need ACK for this packet.
     *             struct sk_buff *skb    Data to send
     */
    int (*writebuf_skb) (int, int, int, struct sk_buff *);
  
    /* Send raw D-Channel-Commands
     * Parameters:
     *             u_char pointer data
     *             int    length of data
     *             int    Flag: 0 = Call form Kernel-Space (use memcpy,
     *                              no schedule allowed) 
     *                          1 = Data is in User-Space (use memcpy_fromfs,
     *                              may schedule)
     *             int    driverId
     *             int    local channel-number (0 ...)
     */
    int (*writecmd)(const u_char*, int, int, int, int);
  
    /* Read raw Status replies
     *             u_char pointer data (volatile)
     *             int    length of buffer
     *             int    Flag: 0 = Call form Kernel-Space (use memcpy,
     *                              no schedule allowed) 
     *                          1 = Data is in User-Space (use memcpy_fromfs,
     *                              may schedule)
     *             int    driverId
     *             int    local channel-number (0 ...)
     */
    int (*readstat)(u_char*, int, int, int, int);
  
    char id[20];
  } isdn_if;
  
  /*
   * Function which must be called by lowlevel-driver at loadtime with
   * the following fields of above struct set:
   *
   * channels     Number of channels that will be supported.
   * hl_hdrlen    Space to preserve in sk_buff's when sending. Drivers, not
   *              supporting sk_buff's should set this to 0.
   * command      Address of Command-Handler.
   * features     Bitwise coded Features of this driver. (use ISDN_FEATURE_...)
   * writebuf_skb Address of Skbuff-Send-Handler.
   * writecmd        "    "  D-Channel  " which accepts raw D-Ch-Commands.
   * readstat        "    "  D-Channel  " which delivers raw Status-Data.
   *
   * The linklevel-driver fills the following fields:
   *
   * channels      Driver-ID assigned to this driver. (Must be used on all
   *               subsequent callbacks.
   * rcvcallb_skb  Address of handler for received Skbuff's.
   * statcallb        "    "     "    for status-changes.
   *
   */
  extern int register_isdn(isdn_if*);
  #include <asm/uaccess.h>
  
  #endif /* __KERNEL__ */
  
  #endif /* __ISDNIF_H__ */
  