/*
 * 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(tty, &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(tty);
	}

	/* 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)
{
	int i, res = 0;
	int n = tty->index;
	const char *name = NULL;
	struct smd_tty_info *info = smd_tty + n;

	for (i = 0; i < smd_tty_channels_len; i++) {
		if (smd_tty_channels[i].id == n) {
			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;
	struct tty_struct *tty = tty_port_tty_get(tport);

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

	tty->driver_data = 0;
	tty_kref_put(tty);
}

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++) {
		tty_port_init(&smd_tty[smd_tty_channels[i].id].port);
		smd_tty[smd_tty_channels[i].id].port.ops = &smd_tty_port_ops;
		tty_register_device(smd_tty_driver, smd_tty_channels[i].id, 0);
	}

	return 0;
}

module_init(smd_tty_init);