// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2016-2017 Linaro Ltd., Rob Herring <robh@kernel.org>
 */
#include <linux/kernel.h>
#include <linux/serdev.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/poll.h>

#define SERPORT_ACTIVE          1

struct serport {
        struct tty_port *port;
        struct tty_struct *tty;
        struct tty_driver *tty_drv;
        int tty_idx;
        unsigned long flags;
};

/*
 * Callback functions from the tty port.
 */

static int ttyport_receive_buf(struct tty_port *port, const unsigned char *cp,
                                const unsigned char *fp, size_t count)
{
        struct serdev_controller *ctrl = port->client_data;
        struct serport *serport = serdev_controller_get_drvdata(ctrl);
        int ret;

        if (!test_bit(SERPORT_ACTIVE, &serport->flags))
                return 0;

        ret = serdev_controller_receive_buf(ctrl, cp, count);

        dev_WARN_ONCE(&ctrl->dev, ret < 0 || ret > count,
                                "receive_buf returns %d (count = %zu)\n",
                                ret, count);
        if (ret < 0)
                return 0;
        else if (ret > count)
                return count;

        return ret;
}

static void ttyport_write_wakeup(struct tty_port *port)
{
        struct serdev_controller *ctrl = port->client_data;
        struct serport *serport = serdev_controller_get_drvdata(ctrl);
        struct tty_struct *tty;

        tty = tty_port_tty_get(port);
        if (!tty)
                return;

        if (test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags) &&
            test_bit(SERPORT_ACTIVE, &serport->flags))
                serdev_controller_write_wakeup(ctrl);

        /* Wake up any tty_wait_until_sent() */
        wake_up_interruptible(&tty->write_wait);

        tty_kref_put(tty);
}

static const struct tty_port_client_operations client_ops = {
        .receive_buf = ttyport_receive_buf,
        .write_wakeup = ttyport_write_wakeup,
};

/*
 * Callback functions from the serdev core.
 */

static int ttyport_write_buf(struct serdev_controller *ctrl, const unsigned char *data, size_t len)
{
        struct serport *serport = serdev_controller_get_drvdata(ctrl);
        struct tty_struct *tty = serport->tty;

        if (!test_bit(SERPORT_ACTIVE, &serport->flags))
                return 0;

        set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
        return tty->ops->write(serport->tty, data, len);
}

static void ttyport_write_flush(struct serdev_controller *ctrl)
{
        struct serport *serport = serdev_controller_get_drvdata(ctrl);
        struct tty_struct *tty = serport->tty;

        tty_driver_flush_buffer(tty);
}

static int ttyport_write_room(struct serdev_controller *ctrl)
{
        struct serport *serport = serdev_controller_get_drvdata(ctrl);
        struct tty_struct *tty = serport->tty;

        return tty_write_room(tty);
}

static int ttyport_open(struct serdev_controller *ctrl)
{
        struct serport *serport = serdev_controller_get_drvdata(ctrl);
        struct tty_struct *tty;
        struct ktermios ktermios;
        int ret;

        tty = tty_init_dev(serport->tty_drv, serport->tty_idx);
        if (IS_ERR(tty))
                return PTR_ERR(tty);
        serport->tty = tty;

        if (!tty->ops->open || !tty->ops->close) {
                ret = -ENODEV;
                goto err_unlock;
        }

        ret = tty->ops->open(serport->tty, NULL);
        if (ret)
                goto err_close;

        tty_unlock(serport->tty);

        /* Bring the UART into a known 8 bits no parity hw fc state */
        ktermios = tty->termios;
        ktermios.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP |
                              INLCR | IGNCR | ICRNL | IXON);
        ktermios.c_oflag &= ~OPOST;
        ktermios.c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
        ktermios.c_cflag &= ~(CSIZE | PARENB);
        ktermios.c_cflag |= CS8;
        ktermios.c_cflag |= CRTSCTS;
        /* Hangups are not supported so make sure to ignore carrier detect. */
        ktermios.c_cflag |= CLOCAL;
        tty_set_termios(tty, &ktermios);

        set_bit(SERPORT_ACTIVE, &serport->flags);

        return 0;

err_close:
        tty->ops->close(tty, NULL);
err_unlock:
        tty_unlock(tty);
        tty_release_struct(tty, serport->tty_idx);

        return ret;
}

static void ttyport_close(struct serdev_controller *ctrl)
{
        struct serport *serport = serdev_controller_get_drvdata(ctrl);
        struct tty_struct *tty = serport->tty;

        clear_bit(SERPORT_ACTIVE, &serport->flags);

        tty_lock(tty);
        if (tty->ops->close)
                tty->ops->close(tty, NULL);
        tty_unlock(tty);

        tty_release_struct(tty, serport->tty_idx);
}

static unsigned int ttyport_set_baudrate(struct serdev_controller *ctrl, unsigned int speed)
{
        struct serport *serport = serdev_controller_get_drvdata(ctrl);
        struct tty_struct *tty = serport->tty;
        struct ktermios ktermios = tty->termios;

        ktermios.c_cflag &= ~CBAUD;
        tty_termios_encode_baud_rate(&ktermios, speed, speed);

        /* tty_set_termios() return not checked as it is always 0 */
        tty_set_termios(tty, &ktermios);
        return ktermios.c_ospeed;
}

static void ttyport_set_flow_control(struct serdev_controller *ctrl, bool enable)
{
        struct serport *serport = serdev_controller_get_drvdata(ctrl);
        struct tty_struct *tty = serport->tty;
        struct ktermios ktermios = tty->termios;

        if (enable)
                ktermios.c_cflag |= CRTSCTS;
        else
                ktermios.c_cflag &= ~CRTSCTS;

        tty_set_termios(tty, &ktermios);
}

static int ttyport_set_parity(struct serdev_controller *ctrl,
                              enum serdev_parity parity)
{
        struct serport *serport = serdev_controller_get_drvdata(ctrl);
        struct tty_struct *tty = serport->tty;
        struct ktermios ktermios = tty->termios;

        ktermios.c_cflag &= ~(PARENB | PARODD | CMSPAR);
        if (parity != SERDEV_PARITY_NONE) {
                ktermios.c_cflag |= PARENB;
                if (parity == SERDEV_PARITY_ODD)
                        ktermios.c_cflag |= PARODD;
        }

        tty_set_termios(tty, &ktermios);

        if ((tty->termios.c_cflag & (PARENB | PARODD | CMSPAR)) !=
            (ktermios.c_cflag & (PARENB | PARODD | CMSPAR)))
                return -EINVAL;

        return 0;
}

static void ttyport_wait_until_sent(struct serdev_controller *ctrl, long timeout)
{
        struct serport *serport = serdev_controller_get_drvdata(ctrl);
        struct tty_struct *tty = serport->tty;

        tty_wait_until_sent(tty, timeout);
}

static int ttyport_get_tiocm(struct serdev_controller *ctrl)
{
        struct serport *serport = serdev_controller_get_drvdata(ctrl);
        struct tty_struct *tty = serport->tty;

        if (!tty->ops->tiocmget)
                return -ENOTSUPP;

        return tty->ops->tiocmget(tty);
}

static int ttyport_set_tiocm(struct serdev_controller *ctrl, unsigned int set, unsigned int clear)
{
        struct serport *serport = serdev_controller_get_drvdata(ctrl);
        struct tty_struct *tty = serport->tty;

        if (!tty->ops->tiocmset)
                return -ENOTSUPP;

        return tty->ops->tiocmset(tty, set, clear);
}

static const struct serdev_controller_ops ctrl_ops = {
        .write_buf = ttyport_write_buf,
        .write_flush = ttyport_write_flush,
        .write_room = ttyport_write_room,
        .open = ttyport_open,
        .close = ttyport_close,
        .set_flow_control = ttyport_set_flow_control,
        .set_parity = ttyport_set_parity,
        .set_baudrate = ttyport_set_baudrate,
        .wait_until_sent = ttyport_wait_until_sent,
        .get_tiocm = ttyport_get_tiocm,
        .set_tiocm = ttyport_set_tiocm,
};

struct device *serdev_tty_port_register(struct tty_port *port,
                                        struct device *parent,
                                        struct tty_driver *drv, int idx)
{
        struct serdev_controller *ctrl;
        struct serport *serport;
        int ret;

        if (!port || !drv || !parent)
                return ERR_PTR(-ENODEV);

        ctrl = serdev_controller_alloc(parent, sizeof(struct serport));
        if (!ctrl)
                return ERR_PTR(-ENOMEM);
        serport = serdev_controller_get_drvdata(ctrl);

        serport->port = port;
        serport->tty_idx = idx;
        serport->tty_drv = drv;

        ctrl->ops = &ctrl_ops;

        port->client_ops = &client_ops;
        port->client_data = ctrl;

        ret = serdev_controller_add(ctrl);
        if (ret)
                goto err_reset_data;

        dev_info(&ctrl->dev, "tty port %s%d registered\n", drv->name, idx);
        return &ctrl->dev;

err_reset_data:
        port->client_data = NULL;
        port->client_ops = &tty_port_default_client_ops;
        serdev_controller_put(ctrl);

        return ERR_PTR(ret);
}

int serdev_tty_port_unregister(struct tty_port *port)
{
        struct serdev_controller *ctrl = port->client_data;
        struct serport *serport = serdev_controller_get_drvdata(ctrl);

        if (!serport)
                return -ENODEV;

        serdev_controller_remove(ctrl);
        port->client_data = NULL;
        port->client_ops = &tty_port_default_client_ops;
        serdev_controller_put(ctrl);

        return 0;
}