tty: n_gsm line discipline
authorAlan Cox <alan@linux.intel.com>
Fri, 26 Mar 2010 11:32:54 +0000 (11:32 +0000)
committerGreg Kroah-Hartman <gregkh@suse.de>
Fri, 21 May 2010 16:34:29 +0000 (09:34 -0700)
Add an implementation of GSM 0710 MUX. The implementation currently supports

- Basic and advanced framing (as either end of the link)
- UI or UIH data frames
- Adaption layer 1-4 (1 and 2 via tty, 3 and 4 as skbuff lists)
- Modem and control messages including the correct retry process
- Flow control

and exposes the MUX channels as a set of virtual tty devices including modem
signals. This is an experimental driver.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
drivers/char/Kconfig
drivers/char/Makefile
drivers/char/n_gsm.c [new file with mode: 0644]
include/linux/gsmmux.h [new file with mode: 0644]
include/linux/tty.h

index 3141dd3..51a5700 100644 (file)
@@ -276,11 +276,18 @@ config N_HDLC
          Allows synchronous HDLC communications with tty device drivers that
          support synchronous HDLC such as the Microgate SyncLink adapter.
 
-         This driver can only be built as a module ( = code which can be
+         This driver can be built as a module ( = code which can be
          inserted in and removed from the running kernel whenever you want).
          The module will be called n_hdlc. If you want to do that, say M
          here.
 
+config N_GSM
+       tristate "GSM MUX line discipline support (EXPERIMENTAL)"
+       depends on EXPERIMENTAL
+       help
+         This line discipline provides support for the GSM MUX protocol and
+         presents the mux as a set of 61 individual tty devices.
+
 config RISCOM8
        tristate "SDL RISCom/8 card support"
        depends on SERIAL_NONSTANDARD
index f957edf..d39be4c 100644 (file)
@@ -40,6 +40,7 @@ obj-$(CONFIG_SYNCLINK)                += synclink.o
 obj-$(CONFIG_SYNCLINKMP)       += synclinkmp.o
 obj-$(CONFIG_SYNCLINK_GT)      += synclink_gt.o
 obj-$(CONFIG_N_HDLC)           += n_hdlc.o
+obj-$(CONFIG_N_GSM)            += n_gsm.o
 obj-$(CONFIG_AMIGA_BUILTIN_SERIAL) += amiserial.o
 obj-$(CONFIG_SX)               += sx.o generic_serial.o
 obj-$(CONFIG_RIO)              += rio/ generic_serial.o
diff --git a/drivers/char/n_gsm.c b/drivers/char/n_gsm.c
new file mode 100644 (file)
index 0000000..c4161d5
--- /dev/null
@@ -0,0 +1,2763 @@
+/*
+ * n_gsm.c GSM 0710 tty multiplexor
+ * Copyright (c) 2009/10 Intel Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ *     * THIS IS A DEVELOPMENT SNAPSHOT IT IS NOT A FINAL RELEASE *
+ *
+ * TO DO:
+ *     Mostly done:    ioctls for setting modes/timing
+ *     Partly done:    hooks so you can pull off frames to non tty devs
+ *     Restart DLCI 0 when it closes ?
+ *     Test basic encoding
+ *     Improve the tx engine
+ *     Resolve tx side locking by adding a queue_head and routing
+ *             all control traffic via it
+ *     General tidy/document
+ *     Review the locking/move to refcounts more (mux now moved to an
+ *             alloc/free model ready)
+ *     Use newest tty open/close port helpers and install hooks
+ *     What to do about power functions ?
+ *     Termios setting and negotiation
+ *     Do we need a 'which mux are you' ioctl to correlate mux and tty sets
+ *
+ */
+
+#include <linux/types.h>
+#include <linux/major.h>
+#include <linux/errno.h>
+#include <linux/signal.h>
+#include <linux/fcntl.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/tty.h>
+#include <linux/timer.h>
+#include <linux/ctype.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/poll.h>
+#include <linux/bitops.h>
+#include <linux/file.h>
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <linux/timer.h>
+#include <linux/tty_flip.h>
+#include <linux/tty_driver.h>
+#include <linux/serial.h>
+#include <linux/kfifo.h>
+#include <linux/skbuff.h>
+#include <linux/gsmmux.h>
+
+static int debug;
+module_param(debug, int, 0600);
+
+#define T1     (HZ/10)
+#define T2     (HZ/3)
+#define N2     3
+
+/* Use long timers for testing at low speed with debug on */
+#ifdef DEBUG_TIMING
+#define T1     HZ
+#define T2     (2 * HZ)
+#endif
+
+/* Semi-arbitary buffer size limits. 0710 is normally run with 32-64 byte
+   limits so this is plenty */
+#define MAX_MRU 512
+#define MAX_MTU 512
+
+/*
+ *     Each block of data we have queued to go out is in the form of
+ *     a gsm_msg which holds everything we need in a link layer independant
+ *     format
+ */
+
+struct gsm_msg {
+       struct gsm_msg *next;
+       u8 addr;                /* DLCI address + flags */
+       u8 ctrl;                /* Control byte + flags */
+       unsigned int len;       /* Length of data block (can be zero) */
+       unsigned char *data;    /* Points into buffer but not at the start */
+       unsigned char buffer[0];
+};
+
+/*
+ *     Each active data link has a gsm_dlci structure associated which ties
+ *     the link layer to an optional tty (if the tty side is open). To avoid
+ *     complexity right now these are only ever freed up when the mux is
+ *     shut down.
+ *
+ *     At the moment we don't free DLCI objects until the mux is torn down
+ *     this avoid object life time issues but might be worth review later.
+ */
+
+struct gsm_dlci {
+       struct gsm_mux *gsm;
+       int addr;
+       int state;
+#define DLCI_CLOSED            0
+#define DLCI_OPENING           1       /* Sending SABM not seen UA */
+#define DLCI_OPEN              2       /* SABM/UA complete */
+#define DLCI_CLOSING           3       /* Sending DISC not seen UA/DM */
+
+       /* Link layer */
+       spinlock_t lock;        /* Protects the internal state */
+       struct timer_list t1;   /* Retransmit timer for SABM and UA */
+       int retries;
+       /* Uplink tty if active */
+       struct tty_port port;   /* The tty bound to this DLCI if there is one */
+       struct kfifo *fifo;     /* Queue fifo for the DLCI */
+       struct kfifo _fifo;     /* For new fifo API porting only */
+       int adaption;           /* Adaption layer in use */
+       u32 modem_rx;           /* Our incoming virtual modem lines */
+       u32 modem_tx;           /* Our outgoing modem lines */
+       int dead;               /* Refuse re-open */
+       /* Flow control */
+       int throttled;          /* Private copy of throttle state */
+       int constipated;        /* Throttle status for outgoing */
+       /* Packetised I/O */
+       struct sk_buff *skb;    /* Frame being sent */
+       struct sk_buff_head skb_list;   /* Queued frames */
+       /* Data handling callback */
+       void (*data)(struct gsm_dlci *dlci, u8 *data, int len);
+};
+
+/* DLCI 0, 62/63 are special or reseved see gsmtty_open */
+
+#define NUM_DLCI               64
+
+/*
+ *     DLCI 0 is used to pass control blocks out of band of the data
+ *     flow (and with a higher link priority). One command can be outstanding
+ *     at a time and we use this structure to manage them. They are created
+ *     and destroyed by the user context, and updated by the receive paths
+ *     and timers
+ */
+
+struct gsm_control {
+       u8 cmd;         /* Command we are issuing */
+       u8 *data;       /* Data for the command in case we retransmit */
+       int len;        /* Length of block for retransmission */
+       int done;       /* Done flag */
+       int error;      /* Error if any */
+};
+
+/*
+ *     Each GSM mux we have is represented by this structure. If we are
+ *     operating as an ldisc then we use this structure as our ldisc
+ *     state. We need to sort out lifetimes and locking with respect
+ *     to the gsm mux array. For now we don't free DLCI objects that
+ *     have been instantiated until the mux itself is terminated.
+ *
+ *     To consider further: tty open versus mux shutdown.
+ */
+
+struct gsm_mux {
+       struct tty_struct *tty;         /* The tty our ldisc is bound to */
+       spinlock_t lock;
+
+       /* Events on the GSM channel */
+       wait_queue_head_t event;
+
+       /* Bits for GSM mode decoding */
+
+       /* Framing Layer */
+       unsigned char *buf;
+       int state;
+#define GSM_SEARCH             0
+#define GSM_START              1
+#define GSM_ADDRESS            2
+#define GSM_CONTROL            3
+#define GSM_LEN                        4
+#define GSM_DATA               5
+#define GSM_FCS                        6
+#define GSM_OVERRUN            7
+       unsigned int len;
+       unsigned int address;
+       unsigned int count;
+       int escape;
+       int encoding;
+       u8 control;
+       u8 fcs;
+       u8 *txframe;                    /* TX framing buffer */
+
+       /* Methods for the receiver side */
+       void (*receive)(struct gsm_mux *gsm, u8 ch);
+       void (*error)(struct gsm_mux *gsm, u8 ch, u8 flag);
+       /* And transmit side */
+       int (*output)(struct gsm_mux *mux, u8 *data, int len);
+
+       /* Link Layer */
+       unsigned int mru;
+       unsigned int mtu;
+       int initiator;                  /* Did we initiate connection */
+       int dead;                       /* Has the mux been shut down */
+       struct gsm_dlci *dlci[NUM_DLCI];
+       int constipated;                /* Asked by remote to shut up */
+
+       spinlock_t tx_lock;
+       unsigned int tx_bytes;          /* TX data outstanding */
+#define TX_THRESH_HI           8192
+#define TX_THRESH_LO           2048
+       struct gsm_msg *tx_head;        /* Pending data packets */
+       struct gsm_msg *tx_tail;
+
+       /* Control messages */
+       struct timer_list t2_timer;     /* Retransmit timer for commands */
+       int cretries;                   /* Command retry counter */
+       struct gsm_control *pending_cmd;/* Our current pending command */
+       spinlock_t control_lock;        /* Protects the pending command */
+
+       /* Configuration */
+       int adaption;           /* 1 or 2 supported */
+       u8 ftype;               /* UI or UIH */
+       int t1, t2;             /* Timers in 1/100th of a sec */
+       int n2;                 /* Retry count */
+
+       /* Statistics (not currently exposed) */
+       unsigned long bad_fcs;
+       unsigned long malformed;
+       unsigned long io_error;
+       unsigned long bad_size;
+       unsigned long unsupported;
+};
+
+
+/*
+ *     Mux objects - needed so that we can translate a tty index into the
+ *     relevant mux and DLCI.
+ */
+
+#define MAX_MUX                4                       /* 256 minors */
+static struct gsm_mux *gsm_mux[MAX_MUX];       /* GSM muxes */
+static spinlock_t gsm_mux_lock;
+
+/*
+ *     This section of the driver logic implements the GSM encodings
+ *     both the basic and the 'advanced'. Reliable transport is not
+ *     supported.
+ */
+
+#define CR                     0x02
+#define EA                     0x01
+#define        PF                      0x10
+
+/* I is special: the rest are ..*/
+#define RR                     0x01
+#define UI                     0x03
+#define RNR                    0x05
+#define REJ                    0x09
+#define DM                     0x0F
+#define SABM                   0x2F
+#define DISC                   0x43
+#define UA                     0x63
+#define        UIH                     0xEF
+
+/* Channel commands */
+#define CMD_NSC                        0x09
+#define CMD_TEST               0x11
+#define CMD_PSC                        0x21
+#define CMD_RLS                        0x29
+#define CMD_FCOFF              0x31
+#define CMD_PN                 0x41
+#define CMD_RPN                        0x49
+#define CMD_FCON               0x51
+#define CMD_CLD                        0x61
+#define CMD_SNC                        0x69
+#define CMD_MSC                        0x71
+
+/* Virtual modem bits */
+#define MDM_FC                 0x01
+#define MDM_RTC                        0x02
+#define MDM_RTR                        0x04
+#define MDM_IC                 0x20
+#define MDM_DV                 0x40
+
+#define GSM0_SOF               0xF9
+#define GSM1_SOF               0x7E
+#define GSM1_ESCAPE            0x7D
+#define GSM1_ESCAPE_BITS       0x20
+#define XON                    0x11
+#define XOFF                   0x13
+
+static const struct tty_port_operations gsm_port_ops;
+
+/*
+ *     CRC table for GSM 0710
+ */
+
+static const u8 gsm_fcs8[256] = {
+       0x00, 0x91, 0xE3, 0x72, 0x07, 0x96, 0xE4, 0x75,
+       0x0E, 0x9F, 0xED, 0x7C, 0x09, 0x98, 0xEA, 0x7B,
+       0x1C, 0x8D, 0xFF, 0x6E, 0x1B, 0x8A, 0xF8, 0x69,
+       0x12, 0x83, 0xF1, 0x60, 0x15, 0x84, 0xF6, 0x67,
+       0x38, 0xA9, 0xDB, 0x4A, 0x3F, 0xAE, 0xDC, 0x4D,
+       0x36, 0xA7, 0xD5, 0x44, 0x31, 0xA0, 0xD2, 0x43,
+       0x24, 0xB5, 0xC7, 0x56, 0x23, 0xB2, 0xC0, 0x51,
+       0x2A, 0xBB, 0xC9, 0x58, 0x2D, 0xBC, 0xCE, 0x5F,
+       0x70, 0xE1, 0x93, 0x02, 0x77, 0xE6, 0x94, 0x05,
+       0x7E, 0xEF, 0x9D, 0x0C, 0x79, 0xE8, 0x9A, 0x0B,
+       0x6C, 0xFD, 0x8F, 0x1E, 0x6B, 0xFA, 0x88, 0x19,
+       0x62, 0xF3, 0x81, 0x10, 0x65, 0xF4, 0x86, 0x17,
+       0x48, 0xD9, 0xAB, 0x3A, 0x4F, 0xDE, 0xAC, 0x3D,
+       0x46, 0xD7, 0xA5, 0x34, 0x41, 0xD0, 0xA2, 0x33,
+       0x54, 0xC5, 0xB7, 0x26, 0x53, 0xC2, 0xB0, 0x21,
+       0x5A, 0xCB, 0xB9, 0x28, 0x5D, 0xCC, 0xBE, 0x2F,
+       0xE0, 0x71, 0x03, 0x92, 0xE7, 0x76, 0x04, 0x95,
+       0xEE, 0x7F, 0x0D, 0x9C, 0xE9, 0x78, 0x0A, 0x9B,
+       0xFC, 0x6D, 0x1F, 0x8E, 0xFB, 0x6A, 0x18, 0x89,
+       0xF2, 0x63, 0x11, 0x80, 0xF5, 0x64, 0x16, 0x87,
+       0xD8, 0x49, 0x3B, 0xAA, 0xDF, 0x4E, 0x3C, 0xAD,
+       0xD6, 0x47, 0x35, 0xA4, 0xD1, 0x40, 0x32, 0xA3,
+       0xC4, 0x55, 0x27, 0xB6, 0xC3, 0x52, 0x20, 0xB1,
+       0xCA, 0x5B, 0x29, 0xB8, 0xCD, 0x5C, 0x2E, 0xBF,
+       0x90, 0x01, 0x73, 0xE2, 0x97, 0x06, 0x74, 0xE5,
+       0x9E, 0x0F, 0x7D, 0xEC, 0x99, 0x08, 0x7A, 0xEB,
+       0x8C, 0x1D, 0x6F, 0xFE, 0x8B, 0x1A, 0x68, 0xF9,
+       0x82, 0x13, 0x61, 0xF0, 0x85, 0x14, 0x66, 0xF7,
+       0xA8, 0x39, 0x4B, 0xDA, 0xAF, 0x3E, 0x4C, 0xDD,
+       0xA6, 0x37, 0x45, 0xD4, 0xA1, 0x30, 0x42, 0xD3,
+       0xB4, 0x25, 0x57, 0xC6, 0xB3, 0x22, 0x50, 0xC1,
+       0xBA, 0x2B, 0x59, 0xC8, 0xBD, 0x2C, 0x5E, 0xCF
+};
+
+#define INIT_FCS       0xFF
+#define GOOD_FCS       0xCF
+
+/**
+ *     gsm_fcs_add     -       update FCS
+ *     @fcs: Current FCS
+ *     @c: Next data
+ *
+ *     Update the FCS to include c. Uses the algorithm in the specification
+ *     notes.
+ */
+
+static inline u8 gsm_fcs_add(u8 fcs, u8 c)
+{
+       return gsm_fcs8[fcs ^ c];
+}
+
+/**
+ *     gsm_fcs_add_block       -       update FCS for a block
+ *     @fcs: Current FCS
+ *     @c: buffer of data
+ *     @len: length of buffer
+ *
+ *     Update the FCS to include c. Uses the algorithm in the specification
+ *     notes.
+ */
+
+static inline u8 gsm_fcs_add_block(u8 fcs, u8 *c, int len)
+{
+       while (len--)
+               fcs = gsm_fcs8[fcs ^ *c++];
+       return fcs;
+}
+
+/**
+ *     gsm_read_ea             -       read a byte into an EA
+ *     @val: variable holding value
+ *     c: byte going into the EA
+ *
+ *     Processes one byte of an EA. Updates the passed variable
+ *     and returns 1 if the EA is now completely read
+ */
+
+static int gsm_read_ea(unsigned int *val, u8 c)
+{
+       /* Add the next 7 bits into the value */
+       *val <<= 7;
+       *val |= c >> 1;
+       /* Was this the last byte of the EA 1 = yes*/
+       return c & EA;
+}
+
+/**
+ *     gsm_encode_modem        -       encode modem data bits
+ *     @dlci: DLCI to encode from
+ *
+ *     Returns the correct GSM encoded modem status bits (6 bit field) for
+ *     the current status of the DLCI and attached tty object
+ */
+
+static u8 gsm_encode_modem(const struct gsm_dlci *dlci)
+{
+       u8 modembits = 0;
+       /* FC is true flow control not modem bits */
+       if (dlci->throttled)
+               modembits |= MDM_FC;
+       if (dlci->modem_tx & TIOCM_DTR)
+               modembits |= MDM_RTC;
+       if (dlci->modem_tx & TIOCM_RTS)
+               modembits |= MDM_RTR;
+       if (dlci->modem_tx & TIOCM_RI)
+               modembits |= MDM_IC;
+       if (dlci->modem_tx & TIOCM_CD)
+               modembits |= MDM_DV;
+       return modembits;
+}
+
+/**
+ *     gsm_print_packet        -       display a frame for debug
+ *     @hdr: header to print before decode
+ *     @addr: address EA from the frame
+ *     @cr: C/R bit from the frame
+ *     @control: control including PF bit
+ *     @data: following data bytes
+ *     @dlen: length of data
+ *
+ *     Displays a packet in human readable format for debugging purposes. The
+ *     style is based on amateur radio LAP-B dump display.
+ */
+
+static void gsm_print_packet(const char *hdr, int addr, int cr,
+                                       u8 control, const u8 *data, int dlen)
+{
+       if (!(debug & 1))
+               return;
+
+       printk(KERN_INFO "%s %d) %c: ", hdr, addr, "RC"[cr]);
+
+       switch (control & ~PF) {
+       case SABM:
+               printk(KERN_CONT "SABM");
+               break;
+       case UA:
+               printk(KERN_CONT "UA");
+               break;
+       case DISC:
+               printk(KERN_CONT "DISC");
+               break;
+       case DM:
+               printk(KERN_CONT "DM");
+               break;
+       case UI:
+               printk(KERN_CONT "UI");
+               break;
+       case UIH:
+               printk(KERN_CONT "UIH");
+               break;
+       default:
+               if (!(control & 0x01)) {
+                       printk(KERN_CONT "I N(S)%d N(R)%d",
+                               (control & 0x0E) >> 1, (control & 0xE)>> 5);
+               } else switch (control & 0x0F) {
+               case RR:
+                       printk("RR(%d)", (control & 0xE0) >> 5);
+                       break;
+               case RNR:
+                       printk("RNR(%d)", (control & 0xE0) >> 5);
+                       break;
+               case REJ:
+                       printk("REJ(%d)", (control & 0xE0) >> 5);
+                       break;
+               default:
+                       printk(KERN_CONT "[%02X]", control);
+               }
+       }
+
+       if (control & PF)
+               printk(KERN_CONT "(P)");
+       else
+               printk(KERN_CONT "(F)");
+
+       if (dlen) {
+               int ct = 0;
+               while (dlen--) {
+                       if (ct % 8 == 0)
+                               printk(KERN_CONT "\n    ");
+                       printk(KERN_CONT "%02X ", *data++);
+                       ct++;
+               }
+       }
+       printk(KERN_CONT "\n");
+}
+
+
+/*
+ *     Link level transmission side
+ */
+
+/**
+ *     gsm_stuff_packet        -       bytestuff a packet
+ *     @ibuf: input
+ *     @obuf: output
+ *     @len: length of input
+ *
+ *     Expand a buffer by bytestuffing it. The worst case size change
+ *     is doubling and the caller is responsible for handing out
+ *     suitable sized buffers.
+ */
+
+static int gsm_stuff_frame(const u8 *input, u8 *output, int len)
+{
+       int olen = 0;
+       while (len--) {
+               if (*input == GSM1_SOF || *input == GSM1_ESCAPE
+                   || *input == XON || *input == XOFF) {
+                       *output++ = GSM1_ESCAPE;
+                       *output++ = *input++ ^ GSM1_ESCAPE_BITS;
+                       olen++;
+               } else
+                       *output++ = *input++;
+               olen++;
+       }
+       return olen;
+}
+
+static void hex_packet(const unsigned char *p, int len)
+{
+       int i;
+       for (i = 0; i < len; i++) {
+               if (i && (i % 16) == 0)
+                       printk("\n");
+               printk("%02X ", *p++);
+       }
+       printk("\n");
+}
+
+/**
+ *     gsm_send        -       send a control frame
+ *     @gsm: our GSM mux
+ *     @addr: address for control frame
+ *     @cr: command/response bit
+ *     @control:  control byte including PF bit
+ *
+ *     Format up and transmit a control frame. These do not go via the
+ *     queueing logic as they should be transmitted ahead of data when
+ *     they are needed.
+ *
+ *     FIXME: Lock versus data TX path
+ */
+
+static void gsm_send(struct gsm_mux *gsm, int addr, int cr, int control)
+{
+       int len;
+       u8 cbuf[10];
+       u8 ibuf[3];
+
+       switch (gsm->encoding) {
+       case 0:
+               cbuf[0] = GSM0_SOF;
+               cbuf[1] = (addr << 2) | (cr << 1) | EA;
+               cbuf[2] = control;
+               cbuf[3] = EA;   /* Length of data = 0 */
+               cbuf[4] = 0xFF - gsm_fcs_add_block(INIT_FCS, cbuf + 1, 3);
+               cbuf[5] = GSM0_SOF;
+               len = 6;
+               break;
+       case 1:
+       case 2:
+               /* Control frame + packing (but not frame stuffing) in mode 1 */
+               ibuf[0] = (addr << 2) | (cr << 1) | EA;
+               ibuf[1] = control;
+               ibuf[2] = 0xFF - gsm_fcs_add_block(INIT_FCS, ibuf, 2);
+               /* Stuffing may double the size worst case */
+               len = gsm_stuff_frame(ibuf, cbuf + 1, 3);
+               /* Now add the SOF markers */
+               cbuf[0] = GSM1_SOF;
+               cbuf[len + 1] = GSM1_SOF;
+               /* FIXME: we can omit the lead one in many cases */
+               len += 2;
+               break;
+       default:
+               WARN_ON(1);
+               return;
+       }
+       gsm->output(gsm, cbuf, len);
+       gsm_print_packet("-->", addr, cr, control, NULL, 0);
+}
+
+/**
+ *     gsm_response    -       send a control response
+ *     @gsm: our GSM mux
+ *     @addr: address for control frame
+ *     @control:  control byte including PF bit
+ *
+ *     Format up and transmit a link level response frame.
+ */
+
+static inline void gsm_response(struct gsm_mux *gsm, int addr, int control)
+{
+       gsm_send(gsm, addr, 0, control);
+}
+
+/**
+ *     gsm_command     -       send a control command
+ *     @gsm: our GSM mux
+ *     @addr: address for control frame
+ *     @control:  control byte including PF bit
+ *
+ *     Format up and transmit a link level command frame.
+ */
+
+static inline void gsm_command(struct gsm_mux *gsm, int addr, int control)
+{
+       gsm_send(gsm, addr, 1, control);
+}
+
+/* Data transmission */
+
+#define HDR_LEN                6       /* ADDR CTRL [LEN.2] DATA FCS */
+
+/**
+ *     gsm_data_alloc          -       allocate data frame
+ *     @gsm: GSM mux
+ *     @addr: DLCI address
+ *     @len: length excluding header and FCS
+ *     @ctrl: control byte
+ *
+ *     Allocate a new data buffer for sending frames with data. Space is left
+ *     at the front for header bytes but that is treated as an implementation
+ *     detail and not for the high level code to use
+ */
+
+static struct gsm_msg *gsm_data_alloc(struct gsm_mux *gsm, u8 addr, int len,
+                                                               u8 ctrl)
+{
+       struct gsm_msg *m = kmalloc(sizeof(struct gsm_msg) + len + HDR_LEN,
+                                                               GFP_ATOMIC);
+       if (m == NULL)
+               return NULL;
+       m->data = m->buffer + HDR_LEN - 1;      /* Allow for FCS */
+       m->len = len;
+       m->addr = addr;
+       m->ctrl = ctrl;
+       m->next = NULL;
+       return m;
+}
+
+/**
+ *     gsm_data_kick           -       poke the queue
+ *     @gsm: GSM Mux
+ *
+ *     The tty device has called us to indicate that room has appeared in
+ *     the transmit queue. Ram more data into the pipe if we have any
+ *
+ *     FIXME: lock against link layer control transmissions
+ */
+
+static void gsm_data_kick(struct gsm_mux *gsm)
+{
+       struct gsm_msg *msg = gsm->tx_head;
+       int len;
+       int skip_sof = 0;
+
+       /* FIXME: We need to apply this solely to data messages */
+       if (gsm->constipated)
+               return;
+
+       while (gsm->tx_head != NULL) {
+               msg = gsm->tx_head;
+               if (gsm->encoding != 0) {
+                       gsm->txframe[0] = GSM1_SOF;
+                       len = gsm_stuff_frame(msg->data,
+                                               gsm->txframe + 1, msg->len);
+                       gsm->txframe[len + 1] = GSM1_SOF;
+                       len += 2;
+               } else {
+                       gsm->txframe[0] = GSM0_SOF;
+                       memcpy(gsm->txframe + 1 , msg->data, msg->len);
+                       gsm->txframe[msg->len + 1] = GSM0_SOF;
+                       len = msg->len + 2;
+               }
+
+               if (debug & 4) {
+                       printk("gsm_data_kick: \n");
+                       hex_packet(gsm->txframe, len);
+               }
+
+               if (gsm->output(gsm, gsm->txframe + skip_sof,
+                                               len - skip_sof) < 0)
+                       break;
+               /* FIXME: Can eliminate one SOF in many more cases */
+               gsm->tx_head = msg->next;
+               if (gsm->tx_head == NULL)
+                       gsm->tx_tail = NULL;
+               gsm->tx_bytes -= msg->len;
+               kfree(msg);
+               /* For a burst of frames skip the extra SOF within the
+                  burst */
+               skip_sof = 1;
+       }
+}
+
+/**
+ *     __gsm_data_queue                -       queue a UI or UIH frame
+ *     @dlci: DLCI sending the data
+ *     @msg: message queued
+ *
+ *     Add data to the transmit queue and try and get stuff moving
+ *     out of the mux tty if not already doing so. The Caller must hold
+ *     the gsm tx lock.
+ */
+
+static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
+{
+       struct gsm_mux *gsm = dlci->gsm;
+       u8 *dp = msg->data;
+       u8 *fcs = dp + msg->len;
+
+       /* Fill in the header */
+       if (gsm->encoding == 0) {
+               if (msg->len < 128)
+                       *--dp = (msg->len << 1) | EA;
+               else {
+                       *--dp = (msg->len >> 6) | EA;
+                       *--dp = (msg->len & 127) << 1;
+               }
+       }
+
+       *--dp = msg->ctrl;
+       if (gsm->initiator)
+               *--dp = (msg->addr << 2) | 2 | EA;
+       else
+               *--dp = (msg->addr << 2) | EA;
+       *fcs = gsm_fcs_add_block(INIT_FCS, dp , msg->data - dp);
+       /* Ugly protocol layering violation */
+       if (msg->ctrl == UI || msg->ctrl == (UI|PF))
+               *fcs = gsm_fcs_add_block(*fcs, msg->data, msg->len);
+       *fcs = 0xFF - *fcs;
+
+       gsm_print_packet("Q> ", msg->addr, gsm->initiator, msg->ctrl,
+                                                       msg->data, msg->len);
+
+       /* Move the header back and adjust the length, also allow for the FCS
+          now tacked on the end */
+       msg->len += (msg->data - dp) + 1;
+       msg->data = dp;
+
+       /* Add to the actual output queue */
+       if (gsm->tx_tail)
+               gsm->tx_tail->next = msg;
+       else
+               gsm->tx_head = msg;
+       gsm->tx_tail = msg;
+       gsm->tx_bytes += msg->len;
+       gsm_data_kick(gsm);
+}
+
+/**
+ *     gsm_data_queue          -       queue a UI or UIH frame
+ *     @dlci: DLCI sending the data
+ *     @msg: message queued
+ *
+ *     Add data to the transmit queue and try and get stuff moving
+ *     out of the mux tty if not already doing so. Take the
+ *     the gsm tx lock and dlci lock.
+ */
+
+static void gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
+{
+       unsigned long flags;
+       spin_lock_irqsave(&dlci->gsm->tx_lock, flags);
+       __gsm_data_queue(dlci, msg);
+       spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags);
+}
+
+/**
+ *     gsm_dlci_data_output    -       try and push data out of a DLCI
+ *     @gsm: mux
+ *     @dlci: the DLCI to pull data from
+ *
+ *     Pull data from a DLCI and send it into the transmit queue if there
+ *     is data. Keep to the MRU of the mux. This path handles the usual tty
+ *     interface which is a byte stream with optional modem data.
+ *
+ *     Caller must hold the tx_lock of the mux.
+ */
+
+static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci)
+{
+       struct gsm_msg *msg;
+       u8 *dp;
+       int len, size;
+       int h = dlci->adaption - 1;
+
+       len = kfifo_len(dlci->fifo);
+       if (len == 0)
+               return 0;
+
+       /* MTU/MRU count only the data bits */
+       if (len > gsm->mtu)
+               len = gsm->mtu;
+
+       size = len + h;
+
+       msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype);
+       /* FIXME: need a timer or something to kick this so it can't
+          get stuck with no work outstanding and no buffer free */
+       if (msg == NULL)
+               return -ENOMEM;
+       dp = msg->data;
+       switch (dlci->adaption) {
+       case 1: /* Unstructured */
+               break;
+       case 2: /* Unstructed with modem bits. Always one byte as we never
+                  send inline break data */
+               *dp += gsm_encode_modem(dlci);
+               len--;
+               break;
+       }
+       WARN_ON(kfifo_out_locked(dlci->fifo, dp , len, &dlci->lock) != len);
+       __gsm_data_queue(dlci, msg);
+       /* Bytes of data we used up */
+       return size;
+}
+
+/**
+ *     gsm_dlci_data_output_framed  -  try and push data out of a DLCI
+ *     @gsm: mux
+ *     @dlci: the DLCI to pull data from
+ *
+ *     Pull data from a DLCI and send it into the transmit queue if there
+ *     is data. Keep to the MRU of the mux. This path handles framed data
+ *     queued as skbuffs to the DLCI.
+ *
+ *     Caller must hold the tx_lock of the mux.
+ */
+
+static int gsm_dlci_data_output_framed(struct gsm_mux *gsm,
+                                               struct gsm_dlci *dlci)
+{
+       struct gsm_msg *msg;
+       u8 *dp;
+       int len, size;
+       int last = 0, first = 0;
+       int overhead = 0;
+
+       /* One byte per frame is used for B/F flags */
+       if (dlci->adaption == 4)
+               overhead = 1;
+
+       /* dlci->skb is locked by tx_lock */
+       if (dlci->skb == NULL) {
+               dlci->skb = skb_dequeue(&dlci->skb_list);
+               if (dlci->skb == NULL)
+                       return 0;
+               first = 1;
+       }
+       len = dlci->skb->len + overhead;
+
+       /* MTU/MRU count only the data bits */
+       if (len > gsm->mtu) {
+               if (dlci->adaption == 3) {
+                       /* Over long frame, bin it */
+                       kfree_skb(dlci->skb);
+                       dlci->skb = NULL;
+                       return 0;
+               }
+               len = gsm->mtu;
+       } else
+               last = 1;
+
+       size = len + overhead;
+       msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype);
+
+       /* FIXME: need a timer or something to kick this so it can't
+          get stuck with no work outstanding and no buffer free */
+       if (msg == NULL)
+               return -ENOMEM;
+       dp = msg->data;
+
+       if (dlci->adaption == 4) { /* Interruptible framed (Packetised Data) */
+               /* Flag byte to carry the start/end info */
+               *dp++ = last << 7 | first << 6 | 1;     /* EA */
+               len--;
+       }
+       memcpy(dp, skb_pull(dlci->skb, len), len);
+       __gsm_data_queue(dlci, msg);
+       if (last)
+               dlci->skb = NULL;
+       return size;
+}
+
+/**
+ *     gsm_dlci_data_sweep             -       look for data to send
+ *     @gsm: the GSM mux
+ *
+ *     Sweep the GSM mux channels in priority order looking for ones with
+ *     data to send. We could do with optimising this scan a bit. We aim
+ *     to fill the queue totally or up to TX_THRESH_HI bytes. Once we hit
+ *     TX_THRESH_LO we get called again
+ *
+ *     FIXME: We should round robin between groups and in theory you can
+ *     renegotiate DLCI priorities with optional stuff. Needs optimising.
+ */
+
+static void gsm_dlci_data_sweep(struct gsm_mux *gsm)
+{
+       int len;
+       /* Priority ordering: We should do priority with RR of the groups */
+       int i = 1;
+       unsigned long flags;
+
+       spin_lock_irqsave(&gsm->tx_lock, flags);
+       while (i < NUM_DLCI) {
+               struct gsm_dlci *dlci;
+
+               if (gsm->tx_bytes > TX_THRESH_HI)
+                       break;
+               dlci = gsm->dlci[i];
+               if (dlci == NULL || dlci->constipated) {
+                       i++;
+                       continue;
+               }
+               if (dlci->adaption < 3)
+                       len = gsm_dlci_data_output(gsm, dlci);
+               else
+                       len = gsm_dlci_data_output_framed(gsm, dlci);
+               if (len < 0)
+                       return;
+               /* DLCI empty - try the next */
+               if (len == 0)
+                       i++;
+       }
+       spin_unlock_irqrestore(&gsm->tx_lock, flags);
+}
+
+/**
+ *     gsm_dlci_data_kick      -       transmit if possible
+ *     @dlci: DLCI to kick
+ *
+ *     Transmit data from this DLCI if the queue is empty. We can't rely on
+ *     a tty wakeup except when we filled the pipe so we need to fire off
+ *     new data ourselves in other cases.
+ */
+
+static void gsm_dlci_data_kick(struct gsm_dlci *dlci)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&dlci->gsm->tx_lock, flags);
+       /* If we have nothing running then we need to fire up */
+       if (dlci->gsm->tx_bytes == 0)
+               gsm_dlci_data_output(dlci->gsm, dlci);
+       else if (dlci->gsm->tx_bytes < TX_THRESH_LO)
+               gsm_dlci_data_sweep(dlci->gsm);
+       spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags);
+}
+
+/*
+ *     Control message processing
+ */
+
+
+/**
+ *     gsm_control_reply       -       send a response frame to a control
+ *     @gsm: gsm channel
+ *     @cmd: the command to use
+ *     @data: data to follow encoded info
+ *     @dlen: length of data
+ *
+ *     Encode up and queue a UI/UIH frame containing our response.
+ */
+
+static void gsm_control_reply(struct gsm_mux *gsm, int cmd, u8 *data,
+                                       int dlen)
+{
+       struct gsm_msg *msg;
+       msg = gsm_data_alloc(gsm, 0, dlen + 2, gsm->ftype);
+       msg->data[0] = (cmd & 0xFE) << 1 | EA;  /* Clear C/R */
+       msg->data[1] = (dlen << 1) | EA;
+       memcpy(msg->data + 2, data, dlen);
+       gsm_data_queue(gsm->dlci[0], msg);
+}
+
+/**
+ *     gsm_process_modem       -       process received modem status
+ *     @tty: virtual tty bound to the DLCI
+ *     @dlci: DLCI to affect
+ *     @modem: modem bits (full EA)
+ *
+ *     Used when a modem control message or line state inline in adaption
+ *     layer 2 is processed. Sort out the local modem state and throttles
+ */
+
+static void gsm_process_modem(struct tty_struct *tty, struct gsm_dlci *dlci,
+                                                       u32 modem)
+{
+       int  mlines = 0;
+       u8 brk = modem >> 6;
+
+       /* Flow control/ready to communicate */
+       if (modem & MDM_FC) {
+               /* Need to throttle our output on this device */
+               dlci->constipated = 1;
+       }
+       if (modem & MDM_RTC) {
+               mlines |= TIOCM_DSR | TIOCM_DTR;
+               dlci->constipated = 0;
+               gsm_dlci_data_kick(dlci);
+       }
+       /* Map modem bits */
+       if (modem & MDM_RTR)
+               mlines |= TIOCM_RTS | TIOCM_CTS;
+       if (modem & MDM_IC)
+               mlines |= TIOCM_RI;
+       if (modem & MDM_DV)
+               mlines |= TIOCM_CD;
+
+       /* Carrier drop -> hangup */
+       if (tty) {
+               if ((mlines & TIOCM_CD) == 0 && (dlci->modem_rx & TIOCM_CD))
+                       if (!(tty->termios->c_cflag & CLOCAL))
+                               tty_hangup(tty);
+               if (brk & 0x01)
+                       tty_insert_flip_char(tty, 0, TTY_BREAK);
+       }
+       dlci->modem_rx = mlines;
+}
+
+/**
+ *     gsm_control_modem       -       modem status received
+ *     @gsm: GSM channel
+ *     @data: data following command
+ *     @clen: command length
+ *
+ *     We have received a modem status control message. This is used by
+ *     the GSM mux protocol to pass virtual modem line status and optionally
+ *     to indicate break signals. Unpack it, convert to Linux representation
+ *     and if need be stuff a break message down the tty.
+ */
+
+static void gsm_control_modem(struct gsm_mux *gsm, u8 *data, int clen)
+{
+       unsigned int addr = 0;
+       unsigned int modem = 0;
+       struct gsm_dlci *dlci;
+       int len = clen;
+       u8 *dp = data;
+       struct tty_struct *tty;
+
+       while (gsm_read_ea(&addr, *dp++) == 0) {
+               len--;
+               if (len == 0)
+                       return;
+       }
+       /* Must be at least one byte following the EA */
+       len--;
+       if (len <= 0)
+               return;
+
+       addr >>= 1;
+       /* Closed port, or invalid ? */
+       if (addr == 0 || addr >= NUM_DLCI || gsm->dlci[addr] == NULL)
+               return;
+       dlci = gsm->dlci[addr];
+
+       while (gsm_read_ea(&modem, *dp++) == 0) {
+               len--;
+               if (len == 0)
+                       return;
+       }
+       tty = tty_port_tty_get(&dlci->port);
+       gsm_process_modem(tty, dlci, modem);
+       if (tty) {
+               tty_wakeup(tty);
+               tty_kref_put(tty);
+       }
+       gsm_control_reply(gsm, CMD_MSC, data, clen);
+}
+
+/**
+ *     gsm_control_rls         -       remote line status
+ *     @gsm: GSM channel
+ *     @data: data bytes
+ *     @clen: data length
+ *
+ *     The modem sends us a two byte message on the control channel whenever
+ *     it wishes to send us an error state from the virtual link. Stuff
+ *     this into the uplink tty if present
+ */
+
+static void gsm_control_rls(struct gsm_mux *gsm, u8 *data, int clen)
+{
+       struct tty_struct *tty;
+       unsigned int addr = 0 ;
+       u8 bits;
+       int len = clen;
+       u8 *dp = data;
+
+       while (gsm_read_ea(&addr, *dp++) == 0) {
+               len--;
+               if (len == 0)
+                       return;
+       }
+       /* Must be at least one byte following ea */
+       len--;
+       if (len <= 0)
+               return;
+       addr >>= 1;
+       /* Closed port, or invalid ? */
+       if (addr == 0 || addr >= NUM_DLCI || gsm->dlci[addr] == NULL)
+               return;
+       /* No error ? */
+       bits = *dp;
+       if ((bits & 1) == 0)
+               return;
+       /* See if we have an uplink tty */
+       tty = tty_port_tty_get(&gsm->dlci[addr]->port);
+
+       if (tty) {
+               if (bits & 2)
+                       tty_insert_flip_char(tty, 0, TTY_OVERRUN);
+               if (bits & 4)
+                       tty_insert_flip_char(tty, 0, TTY_PARITY);
+               if (bits & 8)
+                       tty_insert_flip_char(tty, 0, TTY_FRAME);
+               tty_flip_buffer_push(tty);
+               tty_kref_put(tty);
+       }
+       gsm_control_reply(gsm, CMD_RLS, data, clen);
+}
+
+static void gsm_dlci_begin_close(struct gsm_dlci *dlci);
+
+/**
+ *     gsm_control_message     -       DLCI 0 control processing
+ *     @gsm: our GSM mux
+ *     @command:  the command EA
+ *     @data: data beyond the command/length EAs
+ *     @clen: length
+ *
+ *     Input processor for control messages from the other end of the link.
+ *     Processes the incoming request and queues a response frame or an
+ *     NSC response if not supported
+ */
+
+static void gsm_control_message(struct gsm_mux *gsm, unsigned int command,
+                                                       u8 *data, int clen)
+{
+       u8 buf[1];
+       switch (command) {
+       case CMD_CLD: {
+               struct gsm_dlci *dlci = gsm->dlci[0];
+               /* Modem wishes to close down */
+               if (dlci) {
+                       dlci->dead = 1;
+                       gsm->dead = 1;
+                       gsm_dlci_begin_close(dlci);
+               }
+               }
+               break;
+       case CMD_TEST:
+               /* Modem wishes to test, reply with the data */
+               gsm_control_reply(gsm, CMD_TEST, data, clen);
+               break;
+       case CMD_FCON:
+               /* Modem wants us to STFU */
+               gsm->constipated = 1;
+               gsm_control_reply(gsm, CMD_FCON, NULL, 0);
+               break;
+       case CMD_FCOFF:
+               /* Modem can accept data again */
+               gsm->constipated = 0;
+               gsm_control_reply(gsm, CMD_FCOFF, NULL, 0);
+               /* Kick the link in case it is idling */
+               gsm_data_kick(gsm);
+               break;
+       case CMD_MSC:
+               /* Out of band modem line change indicator for a DLCI */
+               gsm_control_modem(gsm, data, clen);
+               break;
+       case CMD_RLS:
+               /* Out of band error reception for a DLCI */
+               gsm_control_rls(gsm, data, clen);
+               break;
+       case CMD_PSC:
+               /* Modem wishes to enter power saving state */
+               gsm_control_reply(gsm, CMD_PSC, NULL, 0);
+               break;
+               /* Optional unsupported commands */
+       case CMD_PN:    /* Parameter negotiation */
+       case CMD_RPN:   /* Remote port negotation */
+       case CMD_SNC:   /* Service negotation command */
+       default:
+               /* Reply to bad commands with an NSC */
+               buf[0] = command;
+               gsm_control_reply(gsm, CMD_NSC, buf, 1);
+               break;
+       }
+}
+
+/**
+ *     gsm_control_response    -       process a response to our control
+ *     @gsm: our GSM mux
+ *     @command: the command (response) EA
+ *     @data: data beyond the command/length EA
+ *     @clen: length
+ *
+ *     Process a response to an outstanding command. We only allow a single
+ *     control message in flight so this is fairly easy. All the clean up
+ *     is done by the caller, we just update the fields, flag it as done
+ *     and return
+ */
+
+static void gsm_control_response(struct gsm_mux *gsm, unsigned int command,
+                                                       u8 *data, int clen)
+{
+       struct gsm_control *ctrl;
+       unsigned long flags;
+
+       spin_lock_irqsave(&gsm->control_lock, flags);
+
+       ctrl = gsm->pending_cmd;
+       /* Does the reply match our command */
+       command |= 1;
+       if (ctrl != NULL && (command == ctrl->cmd || command == CMD_NSC)) {
+               /* Our command was replied to, kill the retry timer */
+               del_timer(&gsm->t2_timer);
+               gsm->pending_cmd = NULL;
+               /* Rejected by the other end */
+               if (command == CMD_NSC)
+                       ctrl->error = -EOPNOTSUPP;
+               ctrl->done = 1;
+               wake_up(&gsm->event);
+       }
+       spin_unlock_irqrestore(&gsm->control_lock, flags);
+}
+
+/**
+ *     gsm_control_transmit    -       send control packet
+ *     @gsm: gsm mux
+ *     @ctrl: frame to send
+ *
+ *     Send out a pending control command (called under control lock)
+ */
+
+static void gsm_control_transmit(struct gsm_mux *gsm, struct gsm_control *ctrl)
+{
+       struct gsm_msg *msg = gsm_data_alloc(gsm, 0, ctrl->len + 1,
+                                                       gsm->ftype|PF);
+       if (msg == NULL)
+               return;
+       msg->data[0] = (ctrl->cmd << 1) | 2 | EA;       /* command */
+       memcpy(msg->data + 1, ctrl->data, ctrl->len);
+       gsm_data_queue(gsm->dlci[0], msg);
+}
+
+/**
+ *     gsm_control_retransmit  -       retransmit a control frame
+ *     @data: pointer to our gsm object
+ *
+ *     Called off the T2 timer expiry in order to retransmit control frames
+ *     that have been lost in the system somewhere. The control_lock protects
+ *     us from colliding with another sender or a receive completion event.
+ *     In that situation the timer may still occur in a small window but
+ *     gsm->pending_cmd will be NULL and we just let the timer expire.
+ */
+
+static void gsm_control_retransmit(unsigned long data)
+{
+       struct gsm_mux *gsm = (struct gsm_mux *)data;
+       struct gsm_control *ctrl;
+       unsigned long flags;
+       spin_lock_irqsave(&gsm->control_lock, flags);
+       ctrl = gsm->pending_cmd;
+       if (ctrl) {
+               gsm->cretries--;
+               if (gsm->cretries == 0) {
+                       gsm->pending_cmd = NULL;
+                       ctrl->error = -ETIMEDOUT;
+                       ctrl->done = 1;
+                       spin_unlock_irqrestore(&gsm->control_lock, flags);
+                       wake_up(&gsm->event);
+                       return;
+               }
+               gsm_control_transmit(gsm, ctrl);
+               mod_timer(&gsm->t2_timer, jiffies + gsm->t2 * HZ / 100);
+       }
+       spin_unlock_irqrestore(&gsm->control_lock, flags);
+}
+
+/**
+ *     gsm_control_send        -       send a control frame on DLCI 0
+ *     @gsm: the GSM channel
+ *     @command: command  to send including CR bit
+ *     @data: bytes of data (must be kmalloced)
+ *     @len: length of the block to send
+ *
+ *     Queue and dispatch a control command. Only one command can be
+ *     active at a time. In theory more can be outstanding but the matching
+ *     gets really complicated so for now stick to one outstanding.
+ */
+
+static struct gsm_control *gsm_control_send(struct gsm_mux *gsm,
+               unsigned int command, u8 *data, int clen)
+{
+       struct gsm_control *ctrl = kzalloc(sizeof(struct gsm_control),
+                                               GFP_KERNEL);
+       unsigned long flags;
+       if (ctrl == NULL)
+               return NULL;
+retry:
+       wait_event(gsm->event, gsm->pending_cmd == NULL);
+       spin_lock_irqsave(&gsm->control_lock, flags);
+       if (gsm->pending_cmd != NULL) {
+               spin_unlock_irqrestore(&gsm->control_lock, flags);
+               goto retry;
+       }
+       ctrl->cmd = command;
+       ctrl->data = data;
+       ctrl->len = clen;
+       gsm->pending_cmd = ctrl;
+       gsm->cretries = gsm->n2;
+       mod_timer(&gsm->t2_timer, jiffies + gsm->t2 * HZ / 100);
+       gsm_control_transmit(gsm, ctrl);
+       spin_unlock_irqrestore(&gsm->control_lock, flags);
+       return ctrl;
+}
+
+/**
+ *     gsm_control_wait        -       wait for a control to finish
+ *     @gsm: GSM mux
+ *     @control: control we are waiting on
+ *
+ *     Waits for the control to complete or time out. Frees any used
+ *     resources and returns 0 for success, or an error if the remote
+ *     rejected or ignored the request.
+ */
+
+static int gsm_control_wait(struct gsm_mux *gsm, struct gsm_control *control)
+{
+       int err;
+       wait_event(gsm->event, control->done == 1);
+       err = control->error;
+       kfree(control);
+       return err;
+}
+
+
+/*
+ *     DLCI level handling: Needs krefs
+ */
+
+/*
+ *     State transitions and timers
+ */
+
+/**
+ *     gsm_dlci_close          -       a DLCI has closed
+ *     @dlci: DLCI that closed
+ *
+ *     Perform processing when moving a DLCI into closed state. If there
+ *     is an attached tty this is hung up
+ */
+
+static void gsm_dlci_close(struct gsm_dlci *dlci)
+{
+       del_timer(&dlci->t1);
+       if (debug & 8)
+               printk("DLCI %d goes closed.\n", dlci->addr);
+       dlci->state = DLCI_CLOSED;
+       if (dlci->addr != 0) {
+               struct tty_struct  *tty = tty_port_tty_get(&dlci->port);
+               if (tty) {
+                       tty_hangup(tty);
+                       tty_kref_put(tty);
+               }
+               kfifo_reset(dlci->fifo);
+       } else
+               dlci->gsm->dead = 1;
+       wake_up(&dlci->gsm->event);
+       /* A DLCI 0 close is a MUX termination so we need to kick that
+          back to userspace somehow */
+}
+
+/**
+ *     gsm_dlci_open           -       a DLCI has opened
+ *     @dlci: DLCI that opened
+ *
+ *     Perform processing when moving a DLCI into open state.
+ */
+
+static void gsm_dlci_open(struct gsm_dlci *dlci)
+{
+       /* Note that SABM UA .. SABM UA first UA lost can mean that we go
+          open -> open */
+       del_timer(&dlci->t1);
+       /* This will let a tty open continue */
+       dlci->state = DLCI_OPEN;
+       if (debug & 8)
+               printk("DLCI %d goes open.\n", dlci->addr);
+       wake_up(&dlci->gsm->event);
+}
+
+/**
+ *     gsm_dlci_t1             -       T1 timer expiry
+ *     @dlci: DLCI that opened
+ *
+ *     The T1 timer handles retransmits of control frames (essentially of
+ *     SABM and DISC). We resend the command until the retry count runs out
+ *     in which case an opening port goes back to closed and a closing port
+ *     is simply put into closed state (any further frames from the other
+ *     end will get a DM response)
+ */
+
+static void gsm_dlci_t1(unsigned long data)
+{
+       struct gsm_dlci *dlci = (struct gsm_dlci *)data;
+       struct gsm_mux *gsm = dlci->gsm;
+
+       switch (dlci->state) {
+       case DLCI_OPENING:
+               dlci->retries--;
+               if (dlci->retries) {
+                       gsm_command(dlci->gsm, dlci->addr, SABM|PF);
+                       mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
+               } else
+                       gsm_dlci_close(dlci);
+               break;
+       case DLCI_CLOSING:
+               dlci->retries--;
+               if (dlci->retries) {
+                       gsm_command(dlci->gsm, dlci->addr, DISC|PF);
+                       mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
+               } else
+                       gsm_dlci_close(dlci);
+               break;
+       }
+}
+
+/**
+ *     gsm_dlci_begin_open     -       start channel open procedure
+ *     @dlci: DLCI to open
+ *
+ *     Commence opening a DLCI from the Linux side. We issue SABM messages
+ *     to the modem which should then reply with a UA, at which point we
+ *     will move into open state. Opening is done asynchronously with retry
+ *     running off timers and the responses.
+ */
+
+static void gsm_dlci_begin_open(struct gsm_dlci *dlci)
+{
+       struct gsm_mux *gsm = dlci->gsm;
+       if (dlci->state == DLCI_OPEN || dlci->state == DLCI_OPENING)
+               return;
+       dlci->retries = gsm->n2;
+       dlci->state = DLCI_OPENING;
+       gsm_command(dlci->gsm, dlci->addr, SABM|PF);
+       mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
+}
+
+/**
+ *     gsm_dlci_begin_close    -       start channel open procedure
+ *     @dlci: DLCI to open
+ *
+ *     Commence closing a DLCI from the Linux side. We issue DISC messages
+ *     to the modem which should then reply with a UA, at which point we
+ *     will move into closed state. Closing is done asynchronously with retry
+ *     off timers. We may also receive a DM reply from the other end which
+ *     indicates the channel was already closed.
+ */
+
+static void gsm_dlci_begin_close(struct gsm_dlci *dlci)
+{
+       struct gsm_mux *gsm = dlci->gsm;
+       if (dlci->state == DLCI_CLOSED || dlci->state == DLCI_CLOSING)
+               return;
+       dlci->retries = gsm->n2;
+       dlci->state = DLCI_CLOSING;
+       gsm_command(dlci->gsm, dlci->addr, DISC|PF);
+       mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
+}
+
+/**
+ *     gsm_dlci_data           -       data arrived
+ *     @dlci: channel
+ *     @data: block of bytes received
+ *     @len: length of received block
+ *
+ *     A UI or UIH frame has arrived which contains data for a channel
+ *     other than the control channel. If the relevant virtual tty is
+ *     open we shovel the bits down it, if not we drop them.
+ */
+
+static void gsm_dlci_data(struct gsm_dlci *dlci, u8 *data, int len)
+{
+       /* krefs .. */
+       struct tty_port *port = &dlci->port;
+       struct tty_struct *tty = tty_port_tty_get(port);
+       unsigned int modem = 0;
+
+       if (debug & 16)
+               printk("%d bytes for tty %p\n", len, tty);
+       if (tty) {
+               switch (dlci->adaption)  {
+                       /* Unsupported types */
+                       /* Packetised interruptible data */
+                       case 4:
+                               break;
+                       /* Packetised uininterruptible voice/data */
+                       case 3:
+                               break;
+                       /* Asynchronous serial with line state in each frame */
+                       case 2:
+                               while (gsm_read_ea(&modem, *data++) == 0) {
+                                       len--;
+                                       if (len == 0)
+                                               return;
+                               }
+                               gsm_process_modem(tty, dlci, modem);
+                       /* Line state will go via DLCI 0 controls only */
+                       case 1:
+                       default:
+                               tty_insert_flip_string(tty, data, len);
+                               tty_flip_buffer_push(tty);
+               }
+               tty_kref_put(tty);
+       }
+}
+
+/**
+ *     gsm_dlci_control        -       data arrived on control channel
+ *     @dlci: channel
+ *     @data: block of bytes received
+ *     @len: length of received block
+ *
+ *     A UI or UIH frame has arrived which contains data for DLCI 0 the
+ *     control channel. This should contain a command EA followed by
+ *     control data bytes. The command EA contains a command/response bit
+ *     and we divide up the work accordingly.
+ */
+
+static void gsm_dlci_command(struct gsm_dlci *dlci, u8 *data, int len)
+{
+       /* See what command is involved */
+       unsigned int command = 0;
+       while (len-- > 0) {
+               if (gsm_read_ea(&command, *data++) == 1) {
+                       int clen = *data++;
+                       len--;
+                       /* FIXME: this is properly an EA */
+                       clen >>= 1;
+                       /* Malformed command ? */
+                       if (clen > len)
+                               return;
+                       if (command & 1)
+                               gsm_control_message(dlci->gsm, command,
+                                                               data, clen);
+                       else
+                               gsm_control_response(dlci->gsm, command,
+                                                               data, clen);
+                       return;
+               }
+       }
+}
+
+/*
+ *     Allocate/Free DLCI channels
+ */
+
+/**
+ *     gsm_dlci_alloc          -       allocate a DLCI
+ *     @gsm: GSM mux
+ *     @addr: address of the DLCI
+ *
+ *     Allocate and install a new DLCI object into the GSM mux.
+ *
+ *     FIXME: review locking races
+ */
+
+static struct gsm_dlci *gsm_dlci_alloc(struct gsm_mux *gsm, int addr)
+{
+       struct gsm_dlci *dlci = kzalloc(sizeof(struct gsm_dlci), GFP_ATOMIC);
+       if (dlci == NULL)
+               return NULL;
+       spin_lock_init(&dlci->lock);
+       dlci->fifo = &dlci->_fifo;
+       if (kfifo_alloc(&dlci->_fifo, 4096, GFP_KERNEL) < 0) {
+               kfree(dlci);
+               return NULL;
+       }
+
+       skb_queue_head_init(&dlci->skb_list);
+       init_timer(&dlci->t1);
+       dlci->t1.function = gsm_dlci_t1;
+       dlci->t1.data = (unsigned long)dlci;
+       tty_port_init(&dlci->port);
+       dlci->port.ops = &gsm_port_ops;
+       dlci->gsm = gsm;
+       dlci->addr = addr;
+       dlci->adaption = gsm->adaption;
+       dlci->state = DLCI_CLOSED;
+       if (addr)
+               dlci->data = gsm_dlci_data;
+       else
+               dlci->data = gsm_dlci_command;
+       gsm->dlci[addr] = dlci;
+       return dlci;
+}
+
+/**
+ *     gsm_dlci_free           -       release DLCI
+ *     @dlci: DLCI to destroy
+ *
+ *     Free up a DLCI. Currently to keep the lifetime rules sane we only
+ *     clean up DLCI objects when the MUX closes rather than as the port
+ *     is closed down on both the tty and mux levels.
+ *
+ *     Can sleep.
+ */
+static void gsm_dlci_free(struct gsm_dlci *dlci)
+{
+       struct tty_struct *tty = tty_port_tty_get(&dlci->port);
+       if (tty) {
+               tty_vhangup(tty);
+               tty_kref_put(tty);
+       }
+       del_timer_sync(&dlci->t1);
+       dlci->gsm->dlci[dlci->addr] = NULL;
+       kfifo_free(dlci->fifo);
+       kfree(dlci);
+}
+
+
+/*
+ *     LAPBish link layer logic
+ */
+
+/**
+ *     gsm_queue               -       a GSM frame is ready to process
+ *     @gsm: pointer to our gsm mux
+ *
+ *     At this point in time a frame has arrived and been demangled from
+ *     the line encoding. All the differences between the encodings have
+ *     been handled below us and the frame is unpacked into the structures.
+ *     The fcs holds the header FCS but any data FCS must be added here.
+ */
+
+static void gsm_queue(struct gsm_mux *gsm)
+{
+       struct gsm_dlci *dlci;
+       u8 cr;
+       int address;
+       /* We have to sneak a look at the packet body to do the FCS.
+          A somewhat layering violation in the spec */
+
+       if ((gsm->control & ~PF) == UI)
+               gsm->fcs = gsm_fcs_add_block(gsm->fcs, gsm->buf, gsm->len);
+       if (gsm->fcs != GOOD_FCS) {
+               gsm->bad_fcs++;
+               if (debug & 4)
+                       printk("BAD FCS %02x\n", gsm->fcs);
+               return;
+       }
+       address = gsm->address >> 1;
+       if (address >= NUM_DLCI)
+               goto invalid;
+
+       cr = gsm->address & 1;          /* C/R bit */
+
+       gsm_print_packet("<--", address, cr, gsm->control, gsm->buf, gsm->len);
+
+       cr ^= 1 - gsm->initiator;       /* Flip so 1 always means command */
+       dlci = gsm->dlci[address];
+
+       switch (gsm->control) {
+       case SABM|PF:
+               if (cr == 0)
+                       goto invalid;
+               if (dlci == NULL)
+                       dlci = gsm_dlci_alloc(gsm, address);
+               if (dlci == NULL)
+                       return;
+               if (dlci->dead)
+                       gsm_response(gsm, address, DM);
+               else {
+                       gsm_response(gsm, address, UA);
+                       gsm_dlci_open(dlci);
+               }
+               break;
+       case DISC|PF:
+               if (cr == 0)
+                       goto invalid;
+               if (dlci == NULL || dlci->state == DLCI_CLOSED) {
+                       gsm_response(gsm, address, DM);
+                       return;
+               }
+               /* Real close complete */
+               gsm_response(gsm, address, UA);
+               gsm_dlci_close(dlci);
+               break;
+       case UA:
+       case UA|PF:
+               if (cr == 0 || dlci == NULL)
+                       break;
+               switch (dlci->state) {
+               case DLCI_CLOSING:
+                       gsm_dlci_close(dlci);
+                       break;
+               case DLCI_OPENING:
+                       gsm_dlci_open(dlci);
+                       break;
+               }
+               break;
+       case DM:        /* DM can be valid unsolicited */
+       case DM|PF:
+               if (cr)
+                       goto invalid;
+               if (dlci == NULL)
+                       return;
+               gsm_dlci_close(dlci);
+               break;
+       case UI:
+       case UI|PF:
+       case UIH:
+       case UIH|PF:
+#if 0
+               if (cr)
+                       goto invalid;
+#endif
+               if (dlci == NULL || dlci->state != DLCI_OPEN) {
+                       gsm_command(gsm, address, DM|PF);
+                       return;
+               }
+               dlci->data(dlci, gsm->buf, gsm->len);
+               break;
+       default:
+               goto invalid;
+       }
+       return;
+invalid:
+       gsm->malformed++;
+       return;
+}
+
+
+/**
+ *     gsm0_receive    -       perform processing for non-transparency
+ *     @gsm: gsm data for this ldisc instance
+ *     @c: character
+ *
+ *     Receive bytes in gsm mode 0
+ */
+
+static void gsm0_receive(struct gsm_mux *gsm, unsigned char c)
+{
+       switch (gsm->state) {
+       case GSM_SEARCH:        /* SOF marker */
+               if (c == GSM0_SOF) {
+                       gsm->state = GSM_ADDRESS;
+                       gsm->address = 0;
+                       gsm->len = 0;
+                       gsm->fcs = INIT_FCS;
+               }
+               break;          /* Address EA */
+       case GSM_ADDRESS:
+               gsm->fcs = gsm_fcs_add(gsm->fcs, c);
+               if (gsm_read_ea(&gsm->address, c))
+                       gsm->state = GSM_CONTROL;
+               break;
+       case GSM_CONTROL:       /* Control Byte */
+               gsm->fcs = gsm_fcs_add(gsm->fcs, c);
+               gsm->control = c;
+               gsm->state = GSM_LEN;
+               break;
+       case GSM_LEN:           /* Length EA */
+               gsm->fcs = gsm_fcs_add(gsm->fcs, c);
+               if (gsm_read_ea(&gsm->len, c)) {
+                       if (gsm->len > gsm->mru) {
+                               gsm->bad_size++;
+                               gsm->state = GSM_SEARCH;
+                               break;
+                       }
+                       gsm->count = 0;
+                       gsm->state = GSM_DATA;
+               }
+               break;
+       case GSM_DATA:          /* Data */
+               gsm->buf[gsm->count++] = c;
+               if (gsm->count == gsm->len)
+                       gsm->state = GSM_FCS;
+               break;
+       case GSM_FCS:           /* FCS follows the packet */
+               gsm->fcs = c;
+               gsm_queue(gsm);
+               /* And then back for the next frame */
+               gsm->state = GSM_SEARCH;
+               break;
+       }
+}
+
+/**
+ *     gsm0_receive    -       perform processing for non-transparency
+ *     @gsm: gsm data for this ldisc instance
+ *     @c: character
+ *
+ *     Receive bytes in mode 1 (Advanced option)
+ */
+
+static void gsm1_receive(struct gsm_mux *gsm, unsigned char c)
+{
+       if (c == GSM1_SOF) {
+               /* EOF is only valid in frame if we have got to the data state
+                  and received at least one byte (the FCS) */
+               if (gsm->state == GSM_DATA && gsm->count) {
+                       /* Extract the FCS */
+                       gsm->count--;
+                       gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->buf[gsm->count]);
+                       gsm->len = gsm->count;
+                       gsm_queue(gsm);
+                       gsm->state  = GSM_START;
+                       return;
+               }
+               /* Any partial frame was a runt so go back to start */
+               if (gsm->state != GSM_START) {
+                       gsm->malformed++;
+                       gsm->state = GSM_START;
+               }
+               /* A SOF in GSM_START means we are still reading idling or
+                  framing bytes */
+               return;
+       }
+
+       if (c == GSM1_ESCAPE) {
+               gsm->escape = 1;
+               return;
+       }
+
+       /* Only an unescaped SOF gets us out of GSM search */
+       if (gsm->state == GSM_SEARCH)
+               return;
+
+       if (gsm->escape) {
+               c ^= GSM1_ESCAPE_BITS;
+               gsm->escape = 0;
+       }
+       switch (gsm->state) {
+       case GSM_START:         /* First byte after SOF */
+               gsm->address = 0;
+               gsm->state = GSM_ADDRESS;
+               gsm->fcs = INIT_FCS;
+               /* Drop through */
+       case GSM_ADDRESS:       /* Address continuation */
+               gsm->fcs = gsm_fcs_add(gsm->fcs, c);
+               if (gsm_read_ea(&gsm->address, c))
+                       gsm->state = GSM_CONTROL;
+               break;
+       case GSM_CONTROL:       /* Control Byte */
+               gsm->fcs = gsm_fcs_add(gsm->fcs, c);
+               gsm->control = c;
+               gsm->count = 0;
+               gsm->state = GSM_DATA;
+               break;
+       case GSM_DATA:          /* Data */
+               if (gsm->count > gsm->mru ) {   /* Allow one for the FCS */
+                       gsm->state = GSM_OVERRUN;
+                       gsm->bad_size++;
+               } else
+                       gsm->buf[gsm->count++] = c;
+               break;
+       case GSM_OVERRUN:       /* Over-long - eg a dropped SOF */
+               break;
+       }
+}
+
+/**
+ *     gsm_error               -       handle tty error
+ *     @gsm: ldisc data
+ *     @data: byte received (may be invalid)
+ *     @flag: error received
+ *
+ *     Handle an error in the receipt of data for a frame. Currently we just
+ *     go back to hunting for a SOF.
+ *
+ *     FIXME: better diagnostics ?
+ */
+
+static void gsm_error(struct gsm_mux *gsm,
+                               unsigned char data, unsigned char flag)
+{
+       gsm->state = GSM_SEARCH;
+       gsm->io_error++;
+}
+
+/**
+ *     gsm_cleanup_mux         -       generic GSM protocol cleanup
+ *     @gsm: our mux
+ *
+ *     Clean up the bits of the mux which are the same for all framing
+ *     protocols. Remove the mux from the mux table, stop all the timers
+ *     and then shut down each device hanging up the channels as we go.
+ */
+
+void gsm_cleanup_mux(struct gsm_mux *gsm)
+{
+       int i;
+       struct gsm_dlci *dlci = gsm->dlci[0];
+       struct gsm_msg *txq;
+
+       gsm->dead = 1;
+
+       spin_lock(&gsm_mux_lock);
+       for (i = 0; i < MAX_MUX; i++) {
+               if (gsm_mux[i] == gsm) {
+                       gsm_mux[i] = NULL;
+                       break;
+               }
+       }
+       spin_unlock(&gsm_mux_lock);
+       WARN_ON(i == MAX_MUX);
+
+       del_timer_sync(&gsm->t2_timer);
+       /* Now we are sure T2 has stopped */
+       if (dlci) {
+               dlci->dead = 1;
+               gsm_dlci_begin_close(dlci);
+               wait_event_interruptible(gsm->event,
+                                       dlci->state == DLCI_CLOSED);
+       }
+       /* Free up any link layer users */
+       for (i = 0; i < NUM_DLCI; i++)
+               if (gsm->dlci[i])
+                       gsm_dlci_free(gsm->dlci[i]);
+       /* Now wipe the queues */
+       for (txq = gsm->tx_head; txq != NULL; txq = gsm->tx_head) {
+               gsm->tx_head = txq->next;
+               kfree(txq);
+       }
+       gsm->tx_tail = NULL;
+}
+EXPORT_SYMBOL_GPL(gsm_cleanup_mux);
+
+/**
+ *     gsm_activate_mux        -       generic GSM setup
+ *     @gsm: our mux
+ *
+ *     Set up the bits of the mux which are the same for all framing
+ *     protocols. Add the mux to the mux table so it can be opened and
+ *     finally kick off connecting to DLCI 0 on the modem.
+ */
+
+int gsm_activate_mux(struct gsm_mux *gsm)
+{
+       struct gsm_dlci *dlci;
+       int i = 0;
+
+       init_timer(&gsm->t2_timer);
+       gsm->t2_timer.function = gsm_control_retransmit;
+       gsm->t2_timer.data = (unsigned long)gsm;
+       init_waitqueue_head(&gsm->event);
+       spin_lock_init(&gsm->control_lock);
+       spin_lock_init(&gsm->tx_lock);
+
+       if (gsm->encoding == 0)
+               gsm->receive = gsm0_receive;
+       else
+               gsm->receive = gsm1_receive;
+       gsm->error = gsm_error;
+
+       spin_lock(&gsm_mux_lock);
+       for (i = 0; i < MAX_MUX; i++) {
+               if (gsm_mux[i] == NULL) {
+                       gsm_mux[i] = gsm;
+                       break;
+               }
+       }
+       spin_unlock(&gsm_mux_lock);
+       if (i == MAX_MUX)
+               return -EBUSY;
+
+       dlci = gsm_dlci_alloc(gsm, 0);
+       if (dlci == NULL)
+               return -ENOMEM;
+       gsm->dead = 0;          /* Tty opens are now permissible */
+       return 0;
+}
+EXPORT_SYMBOL_GPL(gsm_activate_mux);
+
+/**
+ *     gsm_free_mux            -       free up a mux
+ *     @mux: mux to free
+ *
+ *     Dispose of allocated resources for a dead mux. No refcounting
+ *     at present so the mux must be truely dead.
+ */
+void gsm_free_mux(struct gsm_mux *gsm)
+{
+       kfree(gsm->txframe);
+       kfree(gsm->buf);
+       kfree(gsm);
+}
+EXPORT_SYMBOL_GPL(gsm_free_mux);
+
+/**
+ *     gsm_alloc_mux           -       allocate a mux
+ *
+ *     Creates a new mux ready for activation.
+ */
+
+struct gsm_mux *gsm_alloc_mux(void)
+{
+       struct gsm_mux *gsm = kzalloc(sizeof(struct gsm_mux), GFP_KERNEL);
+       if (gsm == NULL)
+               return NULL;
+       gsm->buf = kmalloc(MAX_MRU + 1, GFP_KERNEL);
+       if (gsm->buf == NULL) {
+               kfree(gsm);
+               return NULL;
+       }
+       gsm->txframe = kmalloc(2 * MAX_MRU + 2, GFP_KERNEL);
+       if (gsm->txframe == NULL) {
+               kfree(gsm->buf);
+               kfree(gsm);
+               return NULL;
+       }
+       spin_lock_init(&gsm->lock);
+
+       gsm->t1 = T1;
+       gsm->t2 = T2;
+       gsm->n2 = N2;
+       gsm->ftype = UIH;
+       gsm->initiator = 0;
+       gsm->adaption = 1;
+       gsm->encoding = 1;
+       gsm->mru = 64;  /* Default to encoding 1 so these should be 64 */
+       gsm->mtu = 64;
+       gsm->dead = 1;  /* Avoid early tty opens */
+
+       return gsm;
+}
+EXPORT_SYMBOL_GPL(gsm_alloc_mux);
+
+
+
+
+/**
+ *     gsmld_output            -       write to link
+ *     @gsm: our mux
+ *     @data: bytes to output
+ *     @len: size
+ *
+ *     Write a block of data from the GSM mux to the data channel. This
+ *     will eventually be serialized from above but at the moment isn't.
+ */
+
+static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len)
+{
+       if (tty_write_room(gsm->tty) < len) {
+               set_bit(TTY_DO_WRITE_WAKEUP, &gsm->tty->flags);
+               return -ENOSPC;
+       }
+       if (debug & 4) {
+               printk("-->%d bytes out\n", len);
+               hex_packet(data, len);
+       }
+       gsm->tty->ops->write(gsm->tty, data, len);
+       return len;
+}
+
+/**
+ *     gsmld_attach_gsm        -       mode set up
+ *     @tty: our tty structure
+ *     @gsm: our mux
+ *
+ *     Set up the MUX for basic mode and commence connecting to the
+ *     modem. Currently called from the line discipline set up but
+ *     will need moving to an ioctl path.
+ */
+
+static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
+{
+       int ret;
+
+       gsm->tty = tty_kref_get(tty);
+       gsm->output = gsmld_output;
+       ret =  gsm_activate_mux(gsm);
+       if (ret != 0)
+               tty_kref_put(gsm->tty);
+       return ret;
+}
+
+
+/**
+ *     gsmld_detach_gsm        -       stop doing 0710 mux
+ *     @tty: tty atttached to the mux
+ *     @gsm: mux
+ *
+ *     Shutdown and then clean up the resources used by the line discipline
+ */
+
+static void gsmld_detach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
+{
+       WARN_ON(tty != gsm->tty);
+       gsm_cleanup_mux(gsm);
+       tty_kref_put(gsm->tty);
+       gsm->tty = NULL;
+}
+
+static void gsmld_receive_buf(struct tty_struct *tty, const unsigned char *cp,
+                             char *fp, int count)
+{
+       struct gsm_mux *gsm = tty->disc_data;
+       const unsigned char *dp;
+       char *f;
+       int i;
+       char buf[64];
+       char flags;
+
+       if (debug & 4) {
+               printk("Inbytes %dd\n", count);
+               hex_packet(cp, count);
+       }
+
+       for (i = count, dp = cp, f = fp; i; i--, dp++) {
+               flags = *f++;
+               switch (flags) {
+               case TTY_NORMAL:
+                       gsm->receive(gsm, *dp);
+                       break;
+               case TTY_OVERRUN:
+               case TTY_BREAK:
+               case TTY_PARITY:
+               case TTY_FRAME:
+                       gsm->error(gsm, *dp, flags);
+                       break;
+               default:
+                       printk(KERN_ERR "%s: unknown flag %d\n",
+                              tty_name(tty, buf), flags);
+                       break;
+               }
+       }
+       /* FASYNC if needed ? */
+       /* If clogged call tty_throttle(tty); */
+}
+
+/**
+ *     gsmld_chars_in_buffer   -       report available bytes
+ *     @tty: tty device
+ *
+ *     Report the number of characters buffered to be delivered to user
+ *     at this instant in time.
+ *
+ *     Locking: gsm lock
+ */
+
+static ssize_t gsmld_chars_in_buffer(struct tty_struct *tty)
+{
+       return 0;
+}
+
+/**
+ *     gsmld_flush_buffer      -       clean input queue
+ *     @tty:   terminal device
+ *
+ *     Flush the input buffer. Called when the line discipline is
+ *     being closed, when the tty layer wants the buffer flushed (eg
+ *     at hangup).
+ */
+
+static void gsmld_flush_buffer(struct tty_struct *tty)
+{
+}
+
+/**
+ *     gsmld_close             -       close the ldisc for this tty
+ *     @tty: device
+ *
+ *     Called from the terminal layer when this line discipline is
+ *     being shut down, either because of a close or becsuse of a
+ *     discipline change. The function will not be called while other
+ *     ldisc methods are in progress.
+ */
+
+static void gsmld_close(struct tty_struct *tty)
+{
+       struct gsm_mux *gsm = tty->disc_data;
+
+       gsmld_detach_gsm(tty, gsm);
+
+       gsmld_flush_buffer(tty);
+       /* Do other clean up here */
+       gsm_free_mux(gsm);
+}
+
+/**
+ *     gsmld_open              -       open an ldisc
+ *     @tty: terminal to open
+ *
+ *     Called when this line discipline is being attached to the
+ *     terminal device. Can sleep. Called serialized so that no
+ *     other events will occur in parallel. No further open will occur
+ *     until a close.
+ */
+
+static int gsmld_open(struct tty_struct *tty)
+{
+       struct gsm_mux *gsm;
+
+       if (tty->ops->write == NULL)
+               return -EINVAL;
+
+       /* Attach our ldisc data */
+       gsm = gsm_alloc_mux();
+       if (gsm == NULL)
+               return -ENOMEM;
+
+       tty->disc_data = gsm;
+       tty->receive_room = 65536;
+
+       /* Attach the initial passive connection */
+       gsm->encoding = 1;
+       return gsmld_attach_gsm(tty, gsm);
+}
+
+/**
+ *     gsmld_write_wakeup      -       asynchronous I/O notifier
+ *     @tty: tty device
+ *
+ *     Required for the ptys, serial driver etc. since processes
+ *     that attach themselves to the master and rely on ASYNC
+ *     IO must be woken up
+ */
+
+static void gsmld_write_wakeup(struct tty_struct *tty)
+{
+       struct gsm_mux *gsm = tty->disc_data;
+
+       /* Queue poll */
+       clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+       gsm_data_kick(gsm);
+       if (gsm->tx_bytes < TX_THRESH_LO)
+               gsm_dlci_data_sweep(gsm);
+}
+
+/**
+ *     gsmld_read              -       read function for tty
+ *     @tty: tty device
+ *     @file: file object
+ *     @buf: userspace buffer pointer
+ *     @nr: size of I/O
+ *
+ *     Perform reads for the line discipline. We are guaranteed that the
+ *     line discipline will not be closed under us but we may get multiple
+ *     parallel readers and must handle this ourselves. We may also get
+ *     a hangup. Always called in user context, may sleep.
+ *
+ *     This code must be sure never to sleep through a hangup.
+ */
+
+static ssize_t gsmld_read(struct tty_struct *tty, struct file *file,
+                        unsigned char __user *buf, size_t nr)
+{
+       return -EOPNOTSUPP;
+}
+
+/**
+ *     gsmld_write             -       write function for tty
+ *     @tty: tty device
+ *     @file: file object
+ *     @buf: userspace buffer pointer
+ *     @nr: size of I/O
+ *
+ *     Called when the owner of the device wants to send a frame
+ *     itself (or some other control data). The data is transferred
+ *     as-is and must be properly framed and checksummed as appropriate
+ *     by userspace. Frames are either sent whole or not at all as this
+ *     avoids pain user side.
+ */
+
+static ssize_t gsmld_write(struct tty_struct *tty, struct file *file,
+                          const unsigned char *buf, size_t nr)
+{
+       int space = tty_write_room(tty);
+       if (space >= nr)
+               return tty->ops->write(tty, buf, nr);
+       set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+       return -ENOBUFS;
+}
+
+/**
+ *     gsmld_poll              -       poll method for N_GSM0710
+ *     @tty: terminal device
+ *     @file: file accessing it
+ *     @wait: poll table
+ *
+ *     Called when the line discipline is asked to poll() for data or
+ *     for special events. This code is not serialized with respect to
+ *     other events save open/close.
+ *
+ *     This code must be sure never to sleep through a hangup.
+ *     Called without the kernel lock held - fine
+ */
+
+static unsigned int gsmld_poll(struct tty_struct *tty, struct file *file,
+                                                       poll_table *wait)
+{
+       unsigned int mask = 0;
+       struct gsm_mux *gsm = tty->disc_data;
+
+       poll_wait(file, &tty->read_wait, wait);
+       poll_wait(file, &tty->write_wait, wait);
+       if (tty_hung_up_p(file))
+               mask |= POLLHUP;
+       if (!tty_is_writelocked(tty) && tty_write_room(tty) > 0)
+               mask |= POLLOUT | POLLWRNORM;
+       if (gsm->dead)
+               mask |= POLLHUP;
+       return mask;
+}
+
+static int gsmld_config(struct tty_struct *tty, struct gsm_mux *gsm,
+                                                       struct gsm_config *c)
+{
+       int need_close = 0;
+       int need_restart = 0;
+
+       /* Stuff we don't support yet - UI or I frame transport, windowing */
+       if ((c->adaption !=1 && c->adaption != 2) || c->k)
+               return -EOPNOTSUPP;
+       /* Check the MRU/MTU range looks sane */
+       if (c->mru > MAX_MRU || c->mtu > MAX_MTU || c->mru < 8 || c->mtu < 8)
+               return -EINVAL;
+       if (c->n2 < 3)
+               return -EINVAL;
+       if (c->encapsulation > 1)       /* Basic, advanced, no I */
+               return -EINVAL;
+       if (c->initiator > 1)
+               return -EINVAL;
+       if (c->i == 0 || c->i > 2)      /* UIH and UI only */
+               return -EINVAL;
+       /*
+        *      See what is needed for reconfiguration
+        */
+
+       /* Timing fields */
+       if (c->t1 != 0 && c->t1 != gsm->t1)
+               need_restart = 1;
+       if (c->t2 != 0 && c->t2 != gsm->t2)
+               need_restart = 1;
+       if (c->encapsulation != gsm->encoding)
+               need_restart = 1;
+       if (c->adaption != gsm->adaption)
+               need_restart = 1;
+       /* Requires care */
+       if (c->initiator != gsm->initiator)
+               need_close = 1;
+       if (c->mru != gsm->mru)
+               need_restart = 1;
+       if (c->mtu != gsm->mtu)
+               need_restart = 1;
+
+       /*
+        *      Close down what is needed, restart and initiate the new
+        *      configuration
+        */
+
+       if (need_close || need_restart) {
+               gsm_dlci_begin_close(gsm->dlci[0]);
+               /* This will timeout if the link is down due to N2 expiring */
+               wait_event_interruptible(gsm->event,
+                               gsm->dlci[0]->state == DLCI_CLOSED);
+               if (signal_pending(current))
+                       return -EINTR;
+       }
+       if (need_restart)
+               gsm_cleanup_mux(gsm);
+
+       gsm->initiator = c->initiator;
+       gsm->mru = c->mru;
+       gsm->encoding = c->encapsulation;
+       gsm->adaption = c->adaption;
+
+       if (c->i == 1)
+               gsm->ftype = UIH;
+       else if (c->i == 2)
+               gsm->ftype = UI;
+
+       if (c->t1)
+               gsm->t1 = c->t1;
+       if (c->t2)
+               gsm->t2 = c->t2;
+
+       /* FIXME: We need to separate activation/deactivation from adding
+          and removing from the mux array */
+       if (need_restart)
+               gsm_activate_mux(gsm);
+       if (gsm->initiator && need_close)
+               gsm_dlci_begin_open(gsm->dlci[0]);
+       return 0;
+}
+
+static int gsmld_ioctl(struct tty_struct *tty, struct file *file,
+                      unsigned int cmd, unsigned long arg)
+{
+       struct gsm_config c;
+       struct gsm_mux *gsm = tty->disc_data;
+
+       switch (cmd) {
+       case GSMIOC_GETCONF:
+               memset(&c, 0, sizeof(c));
+               c.adaption = gsm->adaption;
+               c.encapsulation = gsm->encoding;
+               c.initiator = gsm->initiator;
+               c.t1 = gsm->t1;
+               c.t2 = gsm->t2;
+               c.t3 = 0;       /* Not supported */
+               c.n2 = gsm->n2;
+               if (gsm->ftype == UIH)
+                       c.i = 1;
+               else
+                       c.i = 2;
+               printk("Ftype %d i %d\n", gsm->ftype, c.i);
+               c.mru = gsm->mru;
+               c.mtu = gsm->mtu;
+               c.k = 0;
+               if (copy_to_user((void *)arg, &c, sizeof(c)))
+                       return -EFAULT;
+               return 0;
+       case GSMIOC_SETCONF:
+               if (copy_from_user(&c, (void *)arg, sizeof(c)))
+                       return -EFAULT;
+               return gsmld_config(tty, gsm, &c);
+       default:
+               return n_tty_ioctl_helper(tty, file, cmd, arg);
+       }
+}
+
+
+/* Line discipline for real tty */
+struct tty_ldisc_ops tty_ldisc_packet = {
+       .owner           = THIS_MODULE,
+       .magic           = TTY_LDISC_MAGIC,
+       .name            = "n_gsm",
+       .open            = gsmld_open,
+       .close           = gsmld_close,
+       .flush_buffer    = gsmld_flush_buffer,
+       .chars_in_buffer = gsmld_chars_in_buffer,
+       .read            = gsmld_read,
+       .write           = gsmld_write,
+       .ioctl           = gsmld_ioctl,
+       .poll            = gsmld_poll,
+       .receive_buf     = gsmld_receive_buf,
+       .write_wakeup    = gsmld_write_wakeup
+};
+
+/*
+ *     Virtual tty side
+ */
+
+#define TX_SIZE                512
+
+static int gsmtty_modem_update(struct gsm_dlci *dlci, u8 brk)
+{
+       u8 modembits[5];
+       struct gsm_control *ctrl;
+       int len = 2;
+
+       if (brk)
+               len++;
+
+       modembits[0] = len << 1 | EA;           /* Data bytes */
+       modembits[1] = dlci->addr << 2 | 3;     /* DLCI, EA, 1 */
+       modembits[2] = gsm_encode_modem(dlci) << 1 | EA;
+       if (brk)
+               modembits[3] = brk << 4 | 2 | EA;       /* Valid, EA */
+       ctrl = gsm_control_send(dlci->gsm, CMD_MSC, modembits, len + 1);
+       if (ctrl == NULL)
+               return -ENOMEM;
+       return gsm_control_wait(dlci->gsm, ctrl);
+}
+
+static int gsm_carrier_raised(struct tty_port *port)
+{
+       struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
+       /* Not yet open so no carrier info */
+       if (dlci->state != DLCI_OPEN)
+               return 0;
+       if (debug & 2)
+               return 1;
+       return dlci->modem_rx & TIOCM_CD;
+}
+
+static void gsm_dtr_rts(struct tty_port *port, int onoff)
+{
+       struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
+       unsigned int modem_tx = dlci->modem_tx;
+       if (onoff)
+               modem_tx |= TIOCM_DTR | TIOCM_RTS;
+       else
+               modem_tx &= ~(TIOCM_DTR | TIOCM_RTS);
+       if (modem_tx != dlci->modem_tx) {
+               dlci->modem_tx = modem_tx;
+               gsmtty_modem_update(dlci, 0);
+       }
+}
+
+static const struct tty_port_operations gsm_port_ops = {
+       .carrier_raised = gsm_carrier_raised,
+       .dtr_rts = gsm_dtr_rts,
+};
+
+
+static int gsmtty_open(struct tty_struct *tty, struct file *filp)
+{
+       struct gsm_mux *gsm;
+       struct gsm_dlci *dlci;
+       struct tty_port *port;
+       unsigned int line = tty->index;
+       unsigned int mux = line >> 6;
+
+       line = line & 0x3F;
+
+       if (mux >= MAX_MUX)
+               return -ENXIO;
+       /* FIXME: we need to lock gsm_mux for lifetimes of ttys eventually */
+       if (gsm_mux[mux] == NULL)
+               return -EUNATCH;
+       if (line == 0 || line > 61)     /* 62/63 reserved */
+               return -ECHRNG;
+       gsm = gsm_mux[mux];
+       if (gsm->dead)
+               return -EL2HLT;
+       dlci = gsm->dlci[line];
+       if (dlci == NULL)
+               dlci = gsm_dlci_alloc(gsm, line);
+       if (dlci == NULL)
+               return -ENOMEM;
+       port = &dlci->port;
+       port->count++;
+       tty->driver_data = dlci;
+       tty_port_tty_set(port, tty);
+
+       dlci->modem_rx = 0;
+       /* We could in theory open and close before we wait - eg if we get
+          a DM straight back. This is ok as that will have caused a hangup */
+       set_bit(ASYNCB_INITIALIZED, &port->flags);
+       /* Start sending off SABM messages */
+       gsm_dlci_begin_open(dlci);
+       /* And wait for virtual carrier */
+       return tty_port_block_til_ready(port, tty, filp);
+}
+
+static void gsmtty_close(struct tty_struct *tty, struct file *filp)
+{
+       struct gsm_dlci *dlci = tty->driver_data;
+       if (dlci == NULL)
+               return;
+       if (tty_port_close_start(&dlci->port, tty, filp) == 0)
+               return;
+       gsm_dlci_begin_close(dlci);
+       tty_port_close_end(&dlci->port, tty);
+       tty_port_tty_set(&dlci->port, NULL);
+}
+
+static void gsmtty_hangup(struct tty_struct *tty)
+{
+       struct gsm_dlci *dlci = tty->driver_data;
+       tty_port_hangup(&dlci->port);
+       gsm_dlci_begin_close(dlci);
+}
+
+static int gsmtty_write(struct tty_struct *tty, const unsigned char *buf,
+                                                                   int len)
+{
+       struct gsm_dlci *dlci = tty->driver_data;
+       /* Stuff the bytes into the fifo queue */
+       int sent = kfifo_in_locked(dlci->fifo, buf, len, &dlci->lock);
+       /* Need to kick the channel */
+       gsm_dlci_data_kick(dlci);
+       return sent;
+}
+
+static int gsmtty_write_room(struct tty_struct *tty)
+{
+       struct gsm_dlci *dlci = tty->driver_data;
+       return TX_SIZE - kfifo_len(dlci->fifo);
+}
+
+static int gsmtty_chars_in_buffer(struct tty_struct *tty)
+{
+       struct gsm_dlci *dlci = tty->driver_data;
+       return kfifo_len(dlci->fifo);
+}
+
+static void gsmtty_flush_buffer(struct tty_struct *tty)
+{
+       struct gsm_dlci *dlci = tty->driver_data;
+       /* Caution needed: If we implement reliable transport classes
+          then the data being transmitted can't simply be junked once
+          it has first hit the stack. Until then we can just blow it
+          away */
+       kfifo_reset(dlci->fifo);
+       /* Need to unhook this DLCI from the transmit queue logic */
+}
+
+static void gsmtty_wait_until_sent(struct tty_struct *tty, int timeout)
+{
+       /* The FIFO handles the queue so the kernel will do the right
+          thing waiting on chars_in_buffer before calling us. No work
+          to do here */
+}
+
+static int gsmtty_tiocmget(struct tty_struct *tty, struct file *filp)
+{
+       struct gsm_dlci *dlci = tty->driver_data;
+       return dlci->modem_rx;
+}
+
+static int gsmtty_tiocmset(struct tty_struct *tty, struct file *filp,
+       unsigned int set, unsigned int clear)
+{
+       struct gsm_dlci *dlci = tty->driver_data;
+       unsigned int modem_tx = dlci->modem_tx;
+
+       modem_tx &= clear;
+       modem_tx |= set;
+
+       if (modem_tx != dlci->modem_tx) {
+               dlci->modem_tx = modem_tx;
+               return gsmtty_modem_update(dlci, 0);
+       }
+       return 0;
+}
+
+
+static int gsmtty_ioctl(struct tty_struct *tty, struct file *filp,
+                       unsigned int cmd, unsigned long arg)
+{
+       return -ENOIOCTLCMD;
+}
+
+static void gsmtty_set_termios(struct tty_struct *tty, struct ktermios *old)
+{
+       /* For the moment its fixed. In actual fact the speed information
+          for the virtual channel can be propogated in both directions by
+          the RPN control message. This however rapidly gets nasty as we
+          then have to remap modem signals each way according to whether
+          our virtual cable is null modem etc .. */
+       tty_termios_copy_hw(tty->termios, old);
+}
+
+static void gsmtty_throttle(struct tty_struct *tty)
+{
+       struct gsm_dlci *dlci = tty->driver_data;
+       if (tty->termios->c_cflag & CRTSCTS)
+               dlci->modem_tx &= ~TIOCM_DTR;
+       dlci->throttled = 1;
+       /* Send an MSC with DTR cleared */
+       gsmtty_modem_update(dlci, 0);
+}
+
+static void gsmtty_unthrottle(struct tty_struct *tty)
+{
+       struct gsm_dlci *dlci = tty->driver_data;
+       if (tty->termios->c_cflag & CRTSCTS)
+               dlci->modem_tx |= TIOCM_DTR;
+       dlci->throttled = 0;
+       /* Send an MSC with DTR set */
+       gsmtty_modem_update(dlci, 0);
+}
+
+static int gsmtty_break_ctl(struct tty_struct *tty, int state)
+{
+       struct gsm_dlci *dlci = tty->driver_data;
+       int encode = 0; /* Off */
+
+       if (state == -1)        /* "On indefinitely" - we can't encode this
+                                   properly */
+               encode = 0x0F;
+       else if (state > 0) {
+               encode = state / 200;   /* mS to encoding */
+               if (encode > 0x0F)
+                       encode = 0x0F;  /* Best effort */
+       }
+       return gsmtty_modem_update(dlci, encode);
+}
+
+static struct tty_driver *gsm_tty_driver;
+
+/* Virtual ttys for the demux */
+static const struct tty_operations gsmtty_ops = {
+       .open                   = gsmtty_open,
+       .close                  = gsmtty_close,
+       .write                  = gsmtty_write,
+       .write_room             = gsmtty_write_room,
+       .chars_in_buffer        = gsmtty_chars_in_buffer,
+       .flush_buffer           = gsmtty_flush_buffer,
+       .ioctl                  = gsmtty_ioctl,
+       .throttle               = gsmtty_throttle,
+       .unthrottle             = gsmtty_unthrottle,
+       .set_termios            = gsmtty_set_termios,
+       .hangup                 = gsmtty_hangup,
+       .wait_until_sent        = gsmtty_wait_until_sent,
+       .tiocmget               = gsmtty_tiocmget,
+       .tiocmset               = gsmtty_tiocmset,
+       .break_ctl              = gsmtty_break_ctl,
+};
+
+
+
+static int __init gsm_init(void)
+{
+       /* Fill in our line protocol discipline, and register it */
+       int status = tty_register_ldisc(N_GSM0710, &tty_ldisc_packet);
+       if (status != 0) {
+               printk(KERN_ERR "n_gsm: can't register line discipline (err = %d)\n", status);
+               return status;
+       }
+
+       gsm_tty_driver = alloc_tty_driver(256);
+       if (!gsm_tty_driver) {
+               tty_unregister_ldisc(N_GSM0710);
+               printk(KERN_ERR "gsm_init: tty allocation failed.\n");
+               return -EINVAL;
+       }
+       gsm_tty_driver->owner   = THIS_MODULE;
+       gsm_tty_driver->driver_name     = "gsmtty";
+       gsm_tty_driver->name            = "gsmtty";
+       gsm_tty_driver->major           = 0;    /* Dynamic */
+       gsm_tty_driver->minor_start     = 0;
+       gsm_tty_driver->type            = TTY_DRIVER_TYPE_SERIAL;
+       gsm_tty_driver->subtype = SERIAL_TYPE_NORMAL;
+       gsm_tty_driver->flags   = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV
+                                                       | TTY_DRIVER_HARDWARE_BREAK;
+       gsm_tty_driver->init_termios    = tty_std_termios;
+       /* Fixme */
+       gsm_tty_driver->init_termios.c_lflag &= ~ECHO;
+       tty_set_operations(gsm_tty_driver, &gsmtty_ops);
+
+       spin_lock_init(&gsm_mux_lock);
+
+       if (tty_register_driver(gsm_tty_driver)) {
+               put_tty_driver(gsm_tty_driver);
+               tty_unregister_ldisc(N_GSM0710);
+               printk(KERN_ERR "gsm_init: tty registration failed.\n");
+               return -EBUSY;
+       }
+       printk(KERN_INFO "gsm_init: loaded as %d,%d.\n", gsm_tty_driver->major, gsm_tty_driver->minor_start);
+       return 0;
+}
+
+static void __exit gsm_exit(void)
+{
+       int status = tty_unregister_ldisc(N_GSM0710);
+       if (status != 0)
+               printk(KERN_ERR "n_gsm: can't unregister line discipline (err = %d)\n", status);
+       tty_unregister_driver(gsm_tty_driver);
+       put_tty_driver(gsm_tty_driver);
+       printk(KERN_INFO "gsm_init: unloaded.\n");
+}
+
+module_init(gsm_init);
+module_exit(gsm_exit);
+
+
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_LDISC(N_GSM0710);
diff --git a/include/linux/gsmmux.h b/include/linux/gsmmux.h
new file mode 100644 (file)
index 0000000..378de41
--- /dev/null
@@ -0,0 +1,25 @@
+#ifndef _LINUX_GSMMUX_H
+#define _LINUX_GSMMUX_H
+
+struct gsm_config
+{
+       unsigned int adaption;
+       unsigned int encapsulation;
+       unsigned int initiator;
+       unsigned int t1;
+       unsigned int t2;
+       unsigned int t3;
+       unsigned int n2;
+       unsigned int mru;
+       unsigned int mtu;
+       unsigned int k;
+       unsigned int i;
+       unsigned int unused[8];         /* Padding for expansion without
+                                          breaking stuff */
+};
+
+#define GSMIOC_GETCONF         _IOR('G', 0, struct gsm_config)
+#define GSMIOC_SETCONF         _IOW('G', 1, struct gsm_config)
+
+
+#endif
index 7e605e4..931078b 100644 (file)
@@ -48,6 +48,7 @@
 #define N_PPS          18      /* Pulse per Second */
 #define N_V253         19      /* Codec control over voice modem */
 #define N_CAIF         20      /* CAIF protocol for talking to modems */
+#define N_GSM0710      21      /* GSM 0710 Mux */
 
 /*
  * This character is the same as _POSIX_VDISABLE: it cannot be used as