// SPDX-License-Identifier: GPL-2.0-or-later
/* 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.
 *
 * =====================================================================
 * =====================================================================
 */

#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;

        WARN_ON(!tty || !tty->ops || !skb);

        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;

        WARN_ON(!tty || !tty->ops);

        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;
        platform_device_unregister(&cs->hw.ser->dev);
}

static void gigaset_device_release(struct device *dev)
{
        kfree(container_of(dev, struct ser_cardstate, dev.dev));
}

/*
 * 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;
        }

        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;

        WARN_ON(!tty || !tty->ops);
        /* tiocmset is an optional tty driver method */
        if (!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 = {
        .write_cmd = gigaset_write_cmd,
        .write_room = gigaset_write_room,
        .chars_in_buffer = gigaset_chars_in_buffer,
        .brkchars = gigaset_brkchars,
        .init_bchannel = gigaset_init_bchannel,
        .close_bchannel = gigaset_close_bchannel,
        .initbcshw = gigaset_initbcshw,
        .freebcshw = gigaset_freebcshw,
        .reinitbcshw = gigaset_reinitbcshw,
        .initcshw = gigaset_initcshw,
        .freecshw = gigaset_freecshw,
        .set_modem_ctrl = gigaset_set_modem_ctrl,
        .baud_rate = gigaset_baud_rate,
        .set_line_ctrl = gigaset_set_line_ctrl,
        .send_skb = gigaset_m10x_send_skb,      /* asyncdata.c */
        .handle_input = 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;

        /* Set the amount of data we're willing to receive per call
         * from the hardware driver to half of the input buffer size
         * to leave some reserve.
         * Note: We don't do flow control towards the hardware driver.
         * If more data is received than will fit into the input buffer,
         * it will be dropped and an error will be logged. This should
         * never happen as the device is slow and the buffer size ample.
         */
        tty->receive_room = RBUFSIZE/2;

        /* 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;
}

/*
 * 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;
                }
                /* fall 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,
        .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) {
                rc = -ENOMEM;
                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);