ser-gigaset.c

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/* This is the serial hardware link layer (HLL) for the Gigaset 307x isdn
 * DECT base (aka Sinus 45 isdn) using the RS232 DECT data module M101,
 * written as a line discipline.
 *
 * =====================================================================
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 * =====================================================================
 */

#include "gigaset.h"
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/platform_device.h>
#include <linux/completion.h>

/* Version Information */
#define DRIVER_AUTHOR "Tilman Schmidt"
#define DRIVER_DESC "Serial Driver for Gigaset 307x using Siemens M101"

#define GIGASET_MINORS     1
#define GIGASET_MINOR      0
#define GIGASET_MODULENAME "ser_gigaset"
#define GIGASET_DEVNAME    "ttyGS"

/* length limit according to Siemens 3070usb-protokoll.doc ch. 2.1 */
#define IF_WRITEBUF 264

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");
MODULE_ALIAS_LDISC(N_GIGASET_M101);

static int startmode = SM_ISDN;
module_param(startmode, int, S_IRUGO);
MODULE_PARM_DESC(startmode, "initial operation mode");
static int cidmode = 1;
module_param(cidmode, int, S_IRUGO);
MODULE_PARM_DESC(cidmode, "stay in CID mode when idle");

static struct gigaset_driver *driver;

struct ser_cardstate {
    struct platform_device  dev;
    struct tty_struct   *tty;
    atomic_t        refcnt;
    struct completion   dead_cmp;
};

static struct platform_driver device_driver = {
    .driver = {
        .name = GIGASET_MODULENAME,
    },
};

static void flush_send_queue(struct cardstate *);

/* transmit data from current open skb
 * result: number of bytes sent or error code < 0
 */
static int write_modem(struct cardstate *cs)
{
    struct tty_struct *tty = cs->hw.ser->tty;
    struct bc_state *bcs = &cs->bcs[0]; /* only one channel */
    struct sk_buff *skb = bcs->tx_skb;
    int sent = -EOPNOTSUPP;

    if (!tty || !tty->driver || !skb)
        return -EINVAL;

    if (!skb->len) {
        dev_kfree_skb_any(skb);
        bcs->tx_skb = NULL;
        return -EINVAL;
    }

    set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
    if (tty->ops->write)
        sent = tty->ops->write(tty, skb->data, skb->len);
    gig_dbg(DEBUG_OUTPUT, "write_modem: sent %d", sent);
    if (sent < 0) {
        /* error */
        flush_send_queue(cs);
        return sent;
    }
    skb_pull(skb, sent);
    if (!skb->len) {
        /* skb sent completely */
        gigaset_skb_sent(bcs, skb);

        gig_dbg(DEBUG_INTR, "kfree skb (Adr: %lx)!",
            (unsigned long) skb);
        dev_kfree_skb_any(skb);
        bcs->tx_skb = NULL;
    }
    return sent;
}

/*
 * transmit first queued command buffer
 * result: number of bytes sent or error code < 0
 */
static int send_cb(struct cardstate *cs)
{
    struct tty_struct *tty = cs->hw.ser->tty;
    struct cmdbuf_t *cb, *tcb;
    unsigned long flags;
    int sent = 0;

    if (!tty || !tty->driver)
        return -EFAULT;

    cb = cs->cmdbuf;
    if (!cb)
        return 0;   /* nothing to do */

    if (cb->len) {
        set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
        sent = tty->ops->write(tty, cb->buf + cb->offset, cb->len);
        if (sent < 0) {
            /* error */
            gig_dbg(DEBUG_OUTPUT, "send_cb: write error %d", sent);
            flush_send_queue(cs);
            return sent;
        }
        cb->offset += sent;
        cb->len -= sent;
        gig_dbg(DEBUG_OUTPUT, "send_cb: sent %d, left %u, queued %u",
            sent, cb->len, cs->cmdbytes);
    }

    while (cb && !cb->len) {
        spin_lock_irqsave(&cs->cmdlock, flags);
        cs->cmdbytes -= cs->curlen;
        tcb = cb;
        cs->cmdbuf = cb = cb->next;
        if (cb) {
            cb->prev = NULL;
            cs->curlen = cb->len;
        } else {
            cs->lastcmdbuf = NULL;
            cs->curlen = 0;
        }
        spin_unlock_irqrestore(&cs->cmdlock, flags);

        if (tcb->wake_tasklet)
            tasklet_schedule(tcb->wake_tasklet);
        kfree(tcb);
    }
    return sent;
}

/*
 * send queue tasklet
 * If there is already a skb opened, put data to the transfer buffer
 * by calling "write_modem".
 * Otherwise take a new skb out of the queue.
 */
static void gigaset_modem_fill(unsigned long data)
{
    struct cardstate *cs = (struct cardstate *) data;
    struct bc_state *bcs;
    struct sk_buff *nextskb;
    int sent = 0;

    if (!cs) {
        gig_dbg(DEBUG_OUTPUT, "%s: no cardstate", __func__);
        return;
    }
    bcs = cs->bcs;
    if (!bcs) {
        gig_dbg(DEBUG_OUTPUT, "%s: no cardstate", __func__);
        return;
    }
    if (!bcs->tx_skb) {
        /* no skb is being sent; send command if any */
        sent = send_cb(cs);
        gig_dbg(DEBUG_OUTPUT, "%s: send_cb -> %d", __func__, sent);
        if (sent)
            /* something sent or error */
            return;

        /* no command to send; get skb */
        nextskb = skb_dequeue(&bcs->squeue);
        if (!nextskb)
            /* no skb either, nothing to do */
            return;
        bcs->tx_skb = nextskb;

        gig_dbg(DEBUG_INTR, "Dequeued skb (Adr: %lx)",
            (unsigned long) bcs->tx_skb);
    }

    /* send skb */
    gig_dbg(DEBUG_OUTPUT, "%s: tx_skb", __func__);
    if (write_modem(cs) < 0)
        gig_dbg(DEBUG_OUTPUT, "%s: write_modem failed", __func__);
}

/*
 * throw away all data queued for sending
 */
static void flush_send_queue(struct cardstate *cs)
{
    struct sk_buff *skb;
    struct cmdbuf_t *cb;
    unsigned long flags;

    /* command queue */
    spin_lock_irqsave(&cs->cmdlock, flags);
    while ((cb = cs->cmdbuf) != NULL) {
        cs->cmdbuf = cb->next;
        if (cb->wake_tasklet)
            tasklet_schedule(cb->wake_tasklet);
        kfree(cb);
    }
    cs->cmdbuf = cs->lastcmdbuf = NULL;
    cs->cmdbytes = cs->curlen = 0;
    spin_unlock_irqrestore(&cs->cmdlock, flags);

    /* data queue */
    if (cs->bcs->tx_skb)
        dev_kfree_skb_any(cs->bcs->tx_skb);
    while ((skb = skb_dequeue(&cs->bcs->squeue)) != NULL)
        dev_kfree_skb_any(skb);
}


/* Gigaset Driver Interface */
/* ======================== */

/*
 * queue an AT command string for transmission to the Gigaset device
 * parameters:
 *  cs      controller state structure
 *  buf     buffer containing the string to send
 *  len     number of characters to send
 *  wake_tasklet    tasklet to run when transmission is complete, or NULL
 * return value:
 *  number of bytes queued, or error code < 0
 */
static int gigaset_write_cmd(struct cardstate *cs, struct cmdbuf_t *cb)
{
    unsigned long flags;

    gigaset_dbg_buffer(cs->mstate != MS_LOCKED ?
               DEBUG_TRANSCMD : DEBUG_LOCKCMD,
               "CMD Transmit", cb->len, cb->buf);

    spin_lock_irqsave(&cs->cmdlock, flags);
    cb->prev = cs->lastcmdbuf;
    if (cs->lastcmdbuf)
        cs->lastcmdbuf->next = cb;
    else {
        cs->cmdbuf = cb;
        cs->curlen = cb->len;
    }
    cs->cmdbytes += cb->len;
    cs->lastcmdbuf = cb;
    spin_unlock_irqrestore(&cs->cmdlock, flags);

    spin_lock_irqsave(&cs->lock, flags);
    if (cs->connected)
        tasklet_schedule(&cs->write_tasklet);
    spin_unlock_irqrestore(&cs->lock, flags);
    return cb->len;
}

/*
 * tty_driver.write_room interface routine
 * return number of characters the driver will accept to be written
 * parameter:
 *  controller state structure
 * return value:
 *  number of characters
 */
static int gigaset_write_room(struct cardstate *cs)
{
    unsigned bytes;

    bytes = cs->cmdbytes;
    return bytes < IF_WRITEBUF ? IF_WRITEBUF - bytes : 0;
}

/*
 * tty_driver.chars_in_buffer interface routine
 * return number of characters waiting to be sent
 * parameter:
 *  controller state structure
 * return value:
 *  number of characters
 */
static int gigaset_chars_in_buffer(struct cardstate *cs)
{
    return cs->cmdbytes;
}

/*
 * implementation of ioctl(GIGASET_BRKCHARS)
 * parameter:
 *  controller state structure
 * return value:
 *  -EINVAL (unimplemented function)
 */
static int gigaset_brkchars(struct cardstate *cs, const unsigned char buf[6])
{
    /* not implemented */
    return -EINVAL;
}

/*
 * Open B channel
 * Called by "do_action" in ev-layer.c
 */
static int gigaset_init_bchannel(struct bc_state *bcs)
{
    /* nothing to do for M10x */
    gigaset_bchannel_up(bcs);
    return 0;
}

/*
 * Close B channel
 * Called by "do_action" in ev-layer.c
 */
static int gigaset_close_bchannel(struct bc_state *bcs)
{
    /* nothing to do for M10x */
    gigaset_bchannel_down(bcs);
    return 0;
}

/*
 * Set up B channel structure
 * This is called by "gigaset_initcs" in common.c
 */
static int gigaset_initbcshw(struct bc_state *bcs)
{
    /* unused */
    bcs->hw.ser = NULL;
    return 0;
}

/*
 * Free B channel structure
 * Called by "gigaset_freebcs" in common.c
 */
static void gigaset_freebcshw(struct bc_state *bcs)
{
    /* unused */
}

/*
 * Reinitialize B channel structure
 * This is called by "bcs_reinit" in common.c
 */
static void gigaset_reinitbcshw(struct bc_state *bcs)
{
    /* nothing to do for M10x */
}

/*
 * Free hardware specific device data
 * This will be called by "gigaset_freecs" in common.c
 */
static void gigaset_freecshw(struct cardstate *cs)
{
    tasklet_kill(&cs->write_tasklet);
    if (!cs->hw.ser)
        return;
    dev_set_drvdata(&cs->hw.ser->dev.dev, NULL);
    platform_device_unregister(&cs->hw.ser->dev);
    kfree(cs->hw.ser);
    cs->hw.ser = NULL;
}

static void gigaset_device_release(struct device *dev)
{
    struct platform_device *pdev = to_platform_device(dev);

    /* adapted from platform_device_release() in drivers/base/platform.c */
    kfree(dev->platform_data);
    kfree(pdev->resource);
}

/*
 * Set up hardware specific device data
 * This is called by "gigaset_initcs" in common.c
 */
static int gigaset_initcshw(struct cardstate *cs)
{
    int rc;
    struct ser_cardstate *scs;

    scs = kzalloc(sizeof(struct ser_cardstate), GFP_KERNEL);
    if (!scs) {
        pr_err("out of memory\n");
        return -ENOMEM;
    }
    cs->hw.ser = scs;

    cs->hw.ser->dev.name = GIGASET_MODULENAME;
    cs->hw.ser->dev.id = cs->minor_index;
    cs->hw.ser->dev.dev.release = gigaset_device_release;
    rc = platform_device_register(&cs->hw.ser->dev);
    if (rc != 0) {
        pr_err("error %d registering platform device\n", rc);
        kfree(cs->hw.ser);
        cs->hw.ser = NULL;
        return rc;
    }
    dev_set_drvdata(&cs->hw.ser->dev.dev, cs);

    tasklet_init(&cs->write_tasklet,
             gigaset_modem_fill, (unsigned long) cs);
    return 0;
}

/*
 * set modem control lines
 * Parameters:
 *  card state structure
 *  modem control line state ([TIOCM_DTR]|[TIOCM_RTS])
 * Called by "gigaset_start" and "gigaset_enterconfigmode" in common.c
 * and by "if_lock" and "if_termios" in interface.c
 */
static int gigaset_set_modem_ctrl(struct cardstate *cs, unsigned old_state,
                  unsigned new_state)
{
    struct tty_struct *tty = cs->hw.ser->tty;
    unsigned int set, clear;

    if (!tty || !tty->driver || !tty->ops->tiocmset)
        return -EINVAL;
    set = new_state & ~old_state;
    clear = old_state & ~new_state;
    if (!set && !clear)
        return 0;
    gig_dbg(DEBUG_IF, "tiocmset set %x clear %x", set, clear);
    return tty->ops->tiocmset(tty, set, clear);
}

static int gigaset_baud_rate(struct cardstate *cs, unsigned cflag)
{
    return -EINVAL;
}

static int gigaset_set_line_ctrl(struct cardstate *cs, unsigned cflag)
{
    return -EINVAL;
}

static const struct gigaset_ops ops = {
    gigaset_write_cmd,
    gigaset_write_room,
    gigaset_chars_in_buffer,
    gigaset_brkchars,
    gigaset_init_bchannel,
    gigaset_close_bchannel,
    gigaset_initbcshw,
    gigaset_freebcshw,
    gigaset_reinitbcshw,
    gigaset_initcshw,
    gigaset_freecshw,
    gigaset_set_modem_ctrl,
    gigaset_baud_rate,
    gigaset_set_line_ctrl,
    gigaset_m10x_send_skb,  /* asyncdata.c */
    gigaset_m10x_input, /* asyncdata.c */
};


/* Line Discipline Interface */
/* ========================= */

/* helper functions for cardstate refcounting */
static struct cardstate *cs_get(struct tty_struct *tty)
{
    struct cardstate *cs = tty->disc_data;

    if (!cs || !cs->hw.ser) {
        gig_dbg(DEBUG_ANY, "%s: no cardstate", __func__);
        return NULL;
    }
    atomic_inc(&cs->hw.ser->refcnt);
    return cs;
}

static void cs_put(struct cardstate *cs)
{
    if (atomic_dec_and_test(&cs->hw.ser->refcnt))
        complete(&cs->hw.ser->dead_cmp);
}

/*
 * Called by the tty driver when the line discipline is pushed onto the tty.
 * Called in process context.
 */
static int
gigaset_tty_open(struct tty_struct *tty)
{
    struct cardstate *cs;
    int rc;

    gig_dbg(DEBUG_INIT, "Starting HLL for Gigaset M101");

    pr_info(DRIVER_DESC "\n");

    if (!driver) {
        pr_err("%s: no driver structure\n", __func__);
        return -ENODEV;
    }

    /* allocate memory for our device state and initialize it */
    cs = gigaset_initcs(driver, 1, 1, 0, cidmode, GIGASET_MODULENAME);
    if (!cs) {
        rc = -ENODEV;
        goto error;
    }

    cs->dev = &cs->hw.ser->dev.dev;
    cs->hw.ser->tty = tty;
    atomic_set(&cs->hw.ser->refcnt, 1);
    init_completion(&cs->hw.ser->dead_cmp);

    tty->disc_data = cs;

    /* OK.. Initialization of the datastructures and the HW is done.. Now
     * startup system and notify the LL that we are ready to run
     */
    if (startmode == SM_LOCKED)
        cs->mstate = MS_LOCKED;
    rc = gigaset_start(cs);
    if (rc < 0) {
        tasklet_kill(&cs->write_tasklet);
        goto error;
    }

    gig_dbg(DEBUG_INIT, "Startup of HLL done");
    return 0;

error:
    gig_dbg(DEBUG_INIT, "Startup of HLL failed");
    tty->disc_data = NULL;
    gigaset_freecs(cs);
    return rc;
}

/*
 * Called by the tty driver when the line discipline is removed.
 * Called from process context.
 */
static void
gigaset_tty_close(struct tty_struct *tty)
{
    struct cardstate *cs = tty->disc_data;

    gig_dbg(DEBUG_INIT, "Stopping HLL for Gigaset M101");

    if (!cs) {
        gig_dbg(DEBUG_INIT, "%s: no cardstate", __func__);
        return;
    }

    /* prevent other callers from entering ldisc methods */
    tty->disc_data = NULL;

    if (!cs->hw.ser)
        pr_err("%s: no hw cardstate\n", __func__);
    else {
        /* wait for running methods to finish */
        if (!atomic_dec_and_test(&cs->hw.ser->refcnt))
            wait_for_completion(&cs->hw.ser->dead_cmp);
    }

    /* stop operations */
    gigaset_stop(cs);
    tasklet_kill(&cs->write_tasklet);
    flush_send_queue(cs);
    cs->dev = NULL;
    gigaset_freecs(cs);

    gig_dbg(DEBUG_INIT, "Shutdown of HLL done");
}

/*
 * Called by the tty driver when the tty line is hung up.
 * Wait for I/O to driver to complete and unregister ISDN device.
 * This is already done by the close routine, so just call that.
 * Called from process context.
 */
static int gigaset_tty_hangup(struct tty_struct *tty)
{
    gigaset_tty_close(tty);
    return 0;
}

/*
 * Read on the tty.
 * Unused, received data goes only to the Gigaset driver.
 */
static ssize_t
gigaset_tty_read(struct tty_struct *tty, struct file *file,
         unsigned char __user *buf, size_t count)
{
    return -EAGAIN;
}

/*
 * Write on the tty.
 * Unused, transmit data comes only from the Gigaset driver.
 */
static ssize_t
gigaset_tty_write(struct tty_struct *tty, struct file *file,
          const unsigned char *buf, size_t count)
{
    return -EAGAIN;
}

/*
 * Ioctl on the tty.
 * Called in process context only.
 * May be re-entered by multiple ioctl calling threads.
 */
static int
gigaset_tty_ioctl(struct tty_struct *tty, struct file *file,
          unsigned int cmd, unsigned long arg)
{
    struct cardstate *cs = cs_get(tty);
    int rc, val;
    int __user *p = (int __user *)arg;

    if (!cs)
        return -ENXIO;

    switch (cmd) {

    case FIONREAD:
        /* unused, always return zero */
        val = 0;
        rc = put_user(val, p);
        break;

    case TCFLSH:
        /* flush our buffers and the serial port's buffer */
        switch (arg) {
        case TCIFLUSH:
            /* no own input buffer to flush */
            break;
        case TCIOFLUSH:
        case TCOFLUSH:
            flush_send_queue(cs);
            break;
        }
        /* Pass through */

    default:
        /* pass through to underlying serial device */
        rc = n_tty_ioctl_helper(tty, file, cmd, arg);
        break;
    }
    cs_put(cs);
    return rc;
}

/*
 * Called by the tty driver when a block of data has been received.
 * Will not be re-entered while running but other ldisc functions
 * may be called in parallel.
 * Can be called from hard interrupt level as well as soft interrupt
 * level or mainline.
 * Parameters:
 *  tty tty structure
 *  buf buffer containing received characters
 *  cflags  buffer containing error flags for received characters (ignored)
 *  count   number of received characters
 */
static void
gigaset_tty_receive(struct tty_struct *tty, const unsigned char *buf,
            char *cflags, int count)
{
    struct cardstate *cs = cs_get(tty);
    unsigned tail, head, n;
    struct inbuf_t *inbuf;

    if (!cs)
        return;
    inbuf = cs->inbuf;
    if (!inbuf) {
        dev_err(cs->dev, "%s: no inbuf\n", __func__);
        cs_put(cs);
        return;
    }

    tail = inbuf->tail;
    head = inbuf->head;
    gig_dbg(DEBUG_INTR, "buffer state: %u -> %u, receive %u bytes",
        head, tail, count);

    if (head <= tail) {
        /* possible buffer wraparound */
        n = min_t(unsigned, count, RBUFSIZE - tail);
        memcpy(inbuf->data + tail, buf, n);
        tail = (tail + n) % RBUFSIZE;
        buf += n;
        count -= n;
    }

    if (count > 0) {
        /* tail < head and some data left */
        n = head - tail - 1;
        if (count > n) {
            dev_err(cs->dev,
                "inbuf overflow, discarding %d bytes\n",
                count - n);
            count = n;
        }
        memcpy(inbuf->data + tail, buf, count);
        tail += count;
    }

    gig_dbg(DEBUG_INTR, "setting tail to %u", tail);
    inbuf->tail = tail;

    /* Everything was received .. Push data into handler */
    gig_dbg(DEBUG_INTR, "%s-->BH", __func__);
    gigaset_schedule_event(cs);
    cs_put(cs);
}

/*
 * Called by the tty driver when there's room for more data to send.
 */
static void
gigaset_tty_wakeup(struct tty_struct *tty)
{
    struct cardstate *cs = cs_get(tty);

    clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
    if (!cs)
        return;
    tasklet_schedule(&cs->write_tasklet);
    cs_put(cs);
}

static struct tty_ldisc_ops gigaset_ldisc = {
    .owner      = THIS_MODULE,
    .magic      = TTY_LDISC_MAGIC,
    .name       = "ser_gigaset",
    .open       = gigaset_tty_open,
    .close      = gigaset_tty_close,
    .hangup     = gigaset_tty_hangup,
    .read       = gigaset_tty_read,
    .write      = gigaset_tty_write,
    .ioctl      = gigaset_tty_ioctl,
    .receive_buf    = gigaset_tty_receive,
    .write_wakeup   = gigaset_tty_wakeup,
};


/* Initialization / Shutdown */
/* ========================= */

static int __init ser_gigaset_init(void)
{
    int rc;

    gig_dbg(DEBUG_INIT, "%s", __func__);
    rc = platform_driver_register(&device_driver);
    if (rc != 0) {
        pr_err("error %d registering platform driver\n", rc);
        return rc;
    }

    /* allocate memory for our driver state and initialize it */
    driver = gigaset_initdriver(GIGASET_MINOR, GIGASET_MINORS,
                    GIGASET_MODULENAME, GIGASET_DEVNAME,
                    &ops, THIS_MODULE);
    if (!driver)
        goto error;

    rc = tty_register_ldisc(N_GIGASET_M101, &gigaset_ldisc);
    if (rc != 0) {
        pr_err("error %d registering line discipline\n", rc);
        goto error;
    }

    return 0;

error:
    if (driver) {
        gigaset_freedriver(driver);
        driver = NULL;
    }
    platform_driver_unregister(&device_driver);
    return rc;
}

static void __exit ser_gigaset_exit(void)
{
    int rc;

    gig_dbg(DEBUG_INIT, "%s", __func__);

    if (driver) {
        gigaset_freedriver(driver);
        driver = NULL;
    }

    rc = tty_unregister_ldisc(N_GIGASET_M101);
    if (rc != 0)
        pr_err("error %d unregistering line discipline\n", rc);

    platform_driver_unregister(&device_driver);
}

module_init(ser_gigaset_init);
module_exit(ser_gigaset_exit);