1/* ir-rc5-sz-decoder.c - handle RC5 Streamzap IR Pulse/Space protocol
2 *
3 * Copyright (C) 2010 by Mauro Carvalho Chehab <mchehab@redhat.com>
4 * Copyright (C) 2010 by Jarod Wilson <jarod@redhat.com>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 *  it under the terms of the GNU General Public License as published by
8 *  the Free Software Foundation version 2 of the License.
9 *
10 *  This program is distributed in the hope that it will be useful,
11 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
12 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13 *  GNU General Public License for more details.
14 */
15
16/*
17 * This code handles the 15 bit RC5-ish protocol used by the Streamzap
18 * PC Remote.
19 * It considers a carrier of 36 kHz, with a total of 15 bits, where
20 * the first two bits are start bits, and a third one is a filing bit
21 */
22
23#include "rc-core-priv.h"
24#include <linux/module.h>
25
26#define RC5_SZ_NBITS		15
27#define RC5_UNIT		888888 /* ns */
28#define RC5_BIT_START		(1 * RC5_UNIT)
29#define RC5_BIT_END		(1 * RC5_UNIT)
30
31enum rc5_sz_state {
32	STATE_INACTIVE,
33	STATE_BIT_START,
34	STATE_BIT_END,
35	STATE_FINISHED,
36};
37
38/**
39 * ir_rc5_sz_decode() - Decode one RC-5 Streamzap pulse or space
40 * @dev:	the struct rc_dev descriptor of the device
41 * @ev:		the struct ir_raw_event descriptor of the pulse/space
42 *
43 * This function returns -EINVAL if the pulse violates the state machine
44 */
45static int ir_rc5_sz_decode(struct rc_dev *dev, struct ir_raw_event ev)
46{
47	struct rc5_sz_dec *data = &dev->raw->rc5_sz;
48	u8 toggle, command, system;
49	u32 scancode;
50
51        if (!(dev->raw->enabled_protocols & RC_TYPE_RC5_SZ))
52                return 0;
53
54	if (!is_timing_event(ev)) {
55		if (ev.reset)
56			data->state = STATE_INACTIVE;
57		return 0;
58	}
59
60	if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
61		goto out;
62
63again:
64	IR_dprintk(2, "RC5-sz decode started at state %i (%uus %s)\n",
65		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
66
67	if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
68		return 0;
69
70	switch (data->state) {
71
72	case STATE_INACTIVE:
73		if (!ev.pulse)
74			break;
75
76		data->state = STATE_BIT_START;
77		data->count = 1;
78		data->wanted_bits = RC5_SZ_NBITS;
79		decrease_duration(&ev, RC5_BIT_START);
80		goto again;
81
82	case STATE_BIT_START:
83		if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2))
84			break;
85
86		data->bits <<= 1;
87		if (!ev.pulse)
88			data->bits |= 1;
89		data->count++;
90		data->state = STATE_BIT_END;
91		return 0;
92
93	case STATE_BIT_END:
94		if (!is_transition(&ev, &dev->raw->prev_ev))
95			break;
96
97		if (data->count == data->wanted_bits)
98			data->state = STATE_FINISHED;
99		else
100			data->state = STATE_BIT_START;
101
102		decrease_duration(&ev, RC5_BIT_END);
103		goto again;
104
105	case STATE_FINISHED:
106		if (ev.pulse)
107			break;
108
109		/* RC5-sz */
110		command  = (data->bits & 0x0003F) >> 0;
111		system   = (data->bits & 0x02FC0) >> 6;
112		toggle   = (data->bits & 0x01000) ? 1 : 0;
113		scancode = system << 6 | command;
114
115		IR_dprintk(1, "RC5-sz scancode 0x%04x (toggle: %u)\n",
116			   scancode, toggle);
117
118		rc_keydown(dev, scancode, toggle);
119		data->state = STATE_INACTIVE;
120		return 0;
121	}
122
123out:
124	IR_dprintk(1, "RC5-sz decode failed at state %i (%uus %s)\n",
125		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
126	data->state = STATE_INACTIVE;
127	return -EINVAL;
128}
129
130static struct ir_raw_handler rc5_sz_handler = {
131	.protocols	= RC_TYPE_RC5_SZ,
132	.decode		= ir_rc5_sz_decode,
133};
134
135static int __init ir_rc5_sz_decode_init(void)
136{
137	ir_raw_handler_register(&rc5_sz_handler);
138
139	printk(KERN_INFO "IR RC5 (streamzap) protocol handler initialized\n");
140	return 0;
141}
142
143static void __exit ir_rc5_sz_decode_exit(void)
144{
145	ir_raw_handler_unregister(&rc5_sz_handler);
146}
147
148module_init(ir_rc5_sz_decode_init);
149module_exit(ir_rc5_sz_decode_exit);
150
151MODULE_LICENSE("GPL");
152MODULE_AUTHOR("Jarod Wilson <jarod@redhat.com>");
153MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
154MODULE_DESCRIPTION("RC5 (streamzap) IR protocol decoder");
155