/*
 * Copyright (C) 2007 Google, Inc.
 * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
 * Author: Brian Swetland <swetland@google.com>
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * 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.
 *
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/wait.h>

#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>

#include <mach/msm_smd.h>

#define MAX_SMD_TTYS 32

struct smd_tty_info {
        struct tty_port port;
        smd_channel_t *ch;
};

struct smd_tty_channel_desc {
        int id;
        const char *name;
};

static struct smd_tty_info smd_tty[MAX_SMD_TTYS];

static const struct smd_tty_channel_desc smd_default_tty_channels[] = {
        { .id = 0, .name = "SMD_DS" },
        { .id = 27, .name = "SMD_GPSNMEA" },
};

static const struct smd_tty_channel_desc *smd_tty_channels =
                smd_default_tty_channels;
static int smd_tty_channels_len = ARRAY_SIZE(smd_default_tty_channels);

static void smd_tty_notify(void *priv, unsigned event)
{
        unsigned char *ptr;
        int avail;
        struct smd_tty_info *info = priv;
        struct tty_struct *tty;

        if (event != SMD_EVENT_DATA)
                return;

        tty = tty_port_tty_get(&info->port);
        if (!tty)
                return;

        for (;;) {
                if (test_bit(TTY_THROTTLED, &tty->flags))
                        break;
                avail = smd_read_avail(info->ch);
                if (avail == 0)
                        break;

                avail = tty_prepare_flip_string(&info->port, &ptr, avail);

                if (smd_read(info->ch, ptr, avail) != avail) {
                        /* shouldn't be possible since we're in interrupt
                        ** context here and nobody else could 'steal' our
                        ** characters.
                        */
                        pr_err("OOPS - smd_tty_buffer mismatch?!");
                }

                tty_flip_buffer_push(&info->port);
        }

        /* XXX only when writable and necessary */
        tty_wakeup(tty);
        tty_kref_put(tty);
}

static int smd_tty_port_activate(struct tty_port *tport, struct tty_struct *tty)
{
        struct smd_tty_info *info = container_of(tport, struct smd_tty_info,
                        port);
        int i, res = 0;
        const char *name = NULL;

        for (i = 0; i < smd_tty_channels_len; i++) {
                if (smd_tty_channels[i].id == tty->index) {
                        name = smd_tty_channels[i].name;
                        break;
                }
        }
        if (!name)
                return -ENODEV;

        if (info->ch)
                smd_kick(info->ch);
        else
                res = smd_open(name, &info->ch, info, smd_tty_notify);

        if (!res)
                tty->driver_data = info;

        return res;
}

static void smd_tty_port_shutdown(struct tty_port *tport)
{
        struct smd_tty_info *info = container_of(tport, struct smd_tty_info,
                        port);

        if (info->ch) {
                smd_close(info->ch);
                info->ch = 0;
        }
}

static int smd_tty_open(struct tty_struct *tty, struct file *f)
{
        struct smd_tty_info *info = smd_tty + tty->index;

        return tty_port_open(&info->port, tty, f);
}

static void smd_tty_close(struct tty_struct *tty, struct file *f)
{
        struct smd_tty_info *info = tty->driver_data;

        tty_port_close(&info->port, tty, f);
}

static int smd_tty_write(struct tty_struct *tty,
                         const unsigned char *buf, int len)
{
        struct smd_tty_info *info = tty->driver_data;
        int avail;

        /* if we're writing to a packet channel we will
        ** never be able to write more data than there
        ** is currently space for
        */
        avail = smd_write_avail(info->ch);
        if (len > avail)
                len = avail;

        return smd_write(info->ch, buf, len);
}

static int smd_tty_write_room(struct tty_struct *tty)
{
        struct smd_tty_info *info = tty->driver_data;
        return smd_write_avail(info->ch);
}

static int smd_tty_chars_in_buffer(struct tty_struct *tty)
{
        struct smd_tty_info *info = tty->driver_data;
        return smd_read_avail(info->ch);
}

static void smd_tty_unthrottle(struct tty_struct *tty)
{
        struct smd_tty_info *info = tty->driver_data;
        smd_kick(info->ch);
}

static const struct tty_port_operations smd_tty_port_ops = {
        .shutdown = smd_tty_port_shutdown,
        .activate = smd_tty_port_activate,
};

static const struct tty_operations smd_tty_ops = {
        .open = smd_tty_open,
        .close = smd_tty_close,
        .write = smd_tty_write,
        .write_room = smd_tty_write_room,
        .chars_in_buffer = smd_tty_chars_in_buffer,
        .unthrottle = smd_tty_unthrottle,
};

static struct tty_driver *smd_tty_driver;

static int __init smd_tty_init(void)
{
        int ret, i;

        smd_tty_driver = alloc_tty_driver(MAX_SMD_TTYS);
        if (smd_tty_driver == 0)
                return -ENOMEM;

        smd_tty_driver->driver_name = "smd_tty_driver";
        smd_tty_driver->name = "smd";
        smd_tty_driver->major = 0;
        smd_tty_driver->minor_start = 0;
        smd_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
        smd_tty_driver->subtype = SERIAL_TYPE_NORMAL;
        smd_tty_driver->init_termios = tty_std_termios;
        smd_tty_driver->init_termios.c_iflag = 0;
        smd_tty_driver->init_termios.c_oflag = 0;
        smd_tty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
        smd_tty_driver->init_termios.c_lflag = 0;
        smd_tty_driver->flags = TTY_DRIVER_RESET_TERMIOS |
                TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
        tty_set_operations(smd_tty_driver, &smd_tty_ops);

        ret = tty_register_driver(smd_tty_driver);
        if (ret)
                return ret;

        for (i = 0; i < smd_tty_channels_len; i++) {
                struct tty_port *port = &smd_tty[smd_tty_channels[i].id].port;
                tty_port_init(port);
                port->ops = &smd_tty_port_ops;
                tty_port_register_device(port, smd_tty_driver,
                                smd_tty_channels[i].id, NULL);
        }

        return 0;
}

module_init(smd_tty_init);