// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/slab.h>

#include "speakup.h"
#include "spk_types.h"
#include "spk_priv.h"

struct spk_ldisc_data {
        char buf;
        struct semaphore sem;
        bool buf_free;
};

static struct spk_synth *spk_ttyio_synth;
static struct tty_struct *speakup_tty;
/* mutex to protect against speakup_tty disappearing from underneath us while
 * we are using it. this can happen when the device physically unplugged,
 * while in use. it also serialises access to speakup_tty.
 */
static DEFINE_MUTEX(speakup_tty_mutex);

static int ser_to_dev(int ser, dev_t *dev_no)
{
        if (ser < 0 || ser > (255 - 64)) {
                pr_err("speakup: Invalid ser param. Must be between 0 and 191 inclusive.\n");
                return -EINVAL;
        }

        *dev_no = MKDEV(4, (64 + ser));
        return 0;
}

static int get_dev_to_use(struct spk_synth *synth, dev_t *dev_no)
{
        /* use ser only when dev is not specified */
        if (strcmp(synth->dev_name, SYNTH_DEFAULT_DEV) ||
            synth->ser == SYNTH_DEFAULT_SER)
                return tty_dev_name_to_number(synth->dev_name, dev_no);

        return ser_to_dev(synth->ser, dev_no);
}

static int spk_ttyio_ldisc_open(struct tty_struct *tty)
{
        struct spk_ldisc_data *ldisc_data;

        if (tty->ops->write == NULL)
                return -EOPNOTSUPP;
        speakup_tty = tty;

        ldisc_data = kmalloc(sizeof(struct spk_ldisc_data), GFP_KERNEL);
        if (!ldisc_data)
                return -ENOMEM;

        sema_init(&ldisc_data->sem, 0);
        ldisc_data->buf_free = true;
        speakup_tty->disc_data = ldisc_data;

        return 0;
}

static void spk_ttyio_ldisc_close(struct tty_struct *tty)
{
        mutex_lock(&speakup_tty_mutex);
        kfree(speakup_tty->disc_data);
        speakup_tty = NULL;
        mutex_unlock(&speakup_tty_mutex);
}

static int spk_ttyio_receive_buf2(struct tty_struct *tty,
                                  const unsigned char *cp, char *fp, int count)
{
        struct spk_ldisc_data *ldisc_data = tty->disc_data;

        if (spk_ttyio_synth->read_buff_add) {
                int i;

                for (i = 0; i < count; i++)
                        spk_ttyio_synth->read_buff_add(cp[i]);

                return count;
        }

        if (!ldisc_data->buf_free)
                /* ttyio_in will tty_schedule_flip */
                return 0;

        /* Make sure the consumer has read buf before we have seen
         * buf_free == true and overwrite buf
         */
        mb();

        ldisc_data->buf = cp[0];
        ldisc_data->buf_free = false;
        up(&ldisc_data->sem);

        return 1;
}

static struct tty_ldisc_ops spk_ttyio_ldisc_ops = {
        .owner          = THIS_MODULE,
        .magic          = TTY_LDISC_MAGIC,
        .name           = "speakup_ldisc",
        .open           = spk_ttyio_ldisc_open,
        .close          = spk_ttyio_ldisc_close,
        .receive_buf2   = spk_ttyio_receive_buf2,
};

static int spk_ttyio_out(struct spk_synth *in_synth, const char ch);
static int spk_ttyio_out_unicode(struct spk_synth *in_synth, u16 ch);
static void spk_ttyio_send_xchar(char ch);
static void spk_ttyio_tiocmset(unsigned int set, unsigned int clear);
static unsigned char spk_ttyio_in(void);
static unsigned char spk_ttyio_in_nowait(void);
static void spk_ttyio_flush_buffer(void);

struct spk_io_ops spk_ttyio_ops = {
        .synth_out = spk_ttyio_out,
        .synth_out_unicode = spk_ttyio_out_unicode,
        .send_xchar = spk_ttyio_send_xchar,
        .tiocmset = spk_ttyio_tiocmset,
        .synth_in = spk_ttyio_in,
        .synth_in_nowait = spk_ttyio_in_nowait,
        .flush_buffer = spk_ttyio_flush_buffer,
};
EXPORT_SYMBOL_GPL(spk_ttyio_ops);

static inline void get_termios(struct tty_struct *tty, struct ktermios *out_termios)
{
        down_read(&tty->termios_rwsem);
        *out_termios = tty->termios;
        up_read(&tty->termios_rwsem);
}

static int spk_ttyio_initialise_ldisc(struct spk_synth *synth)
{
        int ret = 0;
        struct tty_struct *tty;
        struct ktermios tmp_termios;
        dev_t dev;

        ret = get_dev_to_use(synth, &dev);
        if (ret)
                return ret;

        tty = tty_kopen(dev);
        if (IS_ERR(tty))
                return PTR_ERR(tty);

        if (tty->ops->open)
                ret = tty->ops->open(tty, NULL);
        else
                ret = -ENODEV;

        if (ret) {
                tty_unlock(tty);
                return ret;
        }

        clear_bit(TTY_HUPPED, &tty->flags);
        /* ensure hardware flow control is enabled */
        get_termios(tty, &tmp_termios);
        if (!(tmp_termios.c_cflag & CRTSCTS)) {
                tmp_termios.c_cflag |= CRTSCTS;
                tty_set_termios(tty, &tmp_termios);
                /*
                 * check c_cflag to see if it's updated as tty_set_termios may not return
                 * error even when no tty bits are changed by the request.
                 */
                get_termios(tty, &tmp_termios);
                if (!(tmp_termios.c_cflag & CRTSCTS))
                        pr_warn("speakup: Failed to set hardware flow control\n");
        }

        tty_unlock(tty);

        ret = tty_set_ldisc(tty, N_SPEAKUP);
        if (ret)
                pr_err("speakup: Failed to set N_SPEAKUP on tty\n");

        return ret;
}

void spk_ttyio_register_ldisc(void)
{
        if (tty_register_ldisc(N_SPEAKUP, &spk_ttyio_ldisc_ops))
                pr_warn("speakup: Error registering line discipline. Most synths won't work.\n");
}

void spk_ttyio_unregister_ldisc(void)
{
        if (tty_unregister_ldisc(N_SPEAKUP))
                pr_warn("speakup: Couldn't unregister ldisc\n");
}

static int spk_ttyio_out(struct spk_synth *in_synth, const char ch)
{
        mutex_lock(&speakup_tty_mutex);
        if (in_synth->alive && speakup_tty && speakup_tty->ops->write) {
                int ret = speakup_tty->ops->write(speakup_tty, &ch, 1);

                mutex_unlock(&speakup_tty_mutex);
                if (ret == 0)
                        /* No room */
                        return 0;
                if (ret < 0) {
                        pr_warn("%s: I/O error, deactivating speakup\n", in_synth->long_name);
                        /* No synth any more, so nobody will restart TTYs, and we thus
                         * need to do it ourselves.  Now that there is no synth we can
                         * let application flood anyway
                         */
                        in_synth->alive = 0;
                        speakup_start_ttys();
                        return 0;
                }
                return 1;
        }

        mutex_unlock(&speakup_tty_mutex);
        return 0;
}

static int spk_ttyio_out_unicode(struct spk_synth *in_synth, u16 ch)
{
        int ret;

        if (ch < 0x80)
                ret = spk_ttyio_out(in_synth, ch);
        else if (ch < 0x800) {
                ret  = spk_ttyio_out(in_synth, 0xc0 | (ch >> 6));
                ret &= spk_ttyio_out(in_synth, 0x80 | (ch & 0x3f));
        } else {
                ret  = spk_ttyio_out(in_synth, 0xe0 | (ch >> 12));
                ret &= spk_ttyio_out(in_synth, 0x80 | ((ch >> 6) & 0x3f));
                ret &= spk_ttyio_out(in_synth, 0x80 | (ch & 0x3f));
        }
        return ret;
}

static int check_tty(struct tty_struct *tty)
{
        if (!tty) {
                pr_warn("%s: I/O error, deactivating speakup\n",
                        spk_ttyio_synth->long_name);
                /* No synth any more, so nobody will restart TTYs, and we thus
                 * need to do it ourselves.  Now that there is no synth we can
                 * let application flood anyway
                 */
                spk_ttyio_synth->alive = 0;
                speakup_start_ttys();
                return 1;
        }

        return 0;
}

static void spk_ttyio_send_xchar(char ch)
{
        mutex_lock(&speakup_tty_mutex);
        if (check_tty(speakup_tty)) {
                mutex_unlock(&speakup_tty_mutex);
                return;
        }

        speakup_tty->ops->send_xchar(speakup_tty, ch);
        mutex_unlock(&speakup_tty_mutex);
}

static void spk_ttyio_tiocmset(unsigned int set, unsigned int clear)
{
        mutex_lock(&speakup_tty_mutex);
        if (check_tty(speakup_tty)) {
                mutex_unlock(&speakup_tty_mutex);
                return;
        }

        speakup_tty->ops->tiocmset(speakup_tty, set, clear);
        mutex_unlock(&speakup_tty_mutex);
}

static unsigned char ttyio_in(int timeout)
{
        struct spk_ldisc_data *ldisc_data = speakup_tty->disc_data;
        char rv;

        if (down_timeout(&ldisc_data->sem, usecs_to_jiffies(timeout)) == -ETIME) {
                if (timeout)
                        pr_warn("spk_ttyio: timeout (%d)  while waiting for input\n",
                                timeout);
                return 0xff;
        }

        rv = ldisc_data->buf;
        /* Make sure we have read buf before we set buf_free to let
         * the producer overwrite it
         */
        mb();
        ldisc_data->buf_free = true;
        /* Let TTY push more characters */
        tty_schedule_flip(speakup_tty->port);

        return rv;
}

static unsigned char spk_ttyio_in(void)
{
        return ttyio_in(SPK_SYNTH_TIMEOUT);
}

static unsigned char spk_ttyio_in_nowait(void)
{
        u8 rv = ttyio_in(0);

        return (rv == 0xff) ? 0 : rv;
}

static void spk_ttyio_flush_buffer(void)
{
        mutex_lock(&speakup_tty_mutex);
        if (check_tty(speakup_tty)) {
                mutex_unlock(&speakup_tty_mutex);
                return;
        }

        if (speakup_tty->ops->flush_buffer)
                speakup_tty->ops->flush_buffer(speakup_tty);

        mutex_unlock(&speakup_tty_mutex);
}

int spk_ttyio_synth_probe(struct spk_synth *synth)
{
        int rv = spk_ttyio_initialise_ldisc(synth);

        if (rv)
                return rv;

        synth->alive = 1;
        spk_ttyio_synth = synth;

        return 0;
}
EXPORT_SYMBOL_GPL(spk_ttyio_synth_probe);

void spk_ttyio_release(void)
{
        if (!speakup_tty)
                return;

        tty_lock(speakup_tty);

        if (speakup_tty->ops->close)
                speakup_tty->ops->close(speakup_tty, NULL);

        tty_ldisc_flush(speakup_tty);
        tty_unlock(speakup_tty);
        tty_kclose(speakup_tty);
}
EXPORT_SYMBOL_GPL(spk_ttyio_release);

const char *spk_ttyio_synth_immediate(struct spk_synth *synth, const char *buff)
{
        u_char ch;

        while ((ch = *buff)) {
                if (ch == '\n')
                        ch = synth->procspeech;
                if (tty_write_room(speakup_tty) < 1 || !synth->io_ops->synth_out(synth, ch))
                        return buff;
                buff++;
        }
        return NULL;
}
EXPORT_SYMBOL_GPL(spk_ttyio_synth_immediate);