ir-rc5-decoder.c revision 52b661449aecc47e652a164c0d8078b31e10aca0 
1/* ir-rc5-decoder.c - handle RC5(x) IR Pulse/Space protocol
2 *
3 * Copyright (C) 2010 by Mauro Carvalho Chehab <mchehab@redhat.com>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 *  it under the terms of the GNU General Public License as published by
7 *  the Free Software Foundation version 2 of the License.
8 *
9 *  This program is distributed in the hope that it will be useful,
10 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
11 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12 *  GNU General Public License for more details.
13 */
14
15/*
16 * This code handles 14 bits RC5 protocols and 20 bits RC5x protocols.
17 * There are other variants that use a different number of bits.
18 * This is currently unsupported.
19 * It considers a carrier of 36 kHz, with a total of 14/20 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
25#define RC5_NBITS		14
26#define RC5X_NBITS		20
27#define CHECK_RC5X_NBITS	8
28#define RC5_UNIT		888888 /* ns */
29#define RC5_BIT_START		(1 * RC5_UNIT)
30#define RC5_BIT_END		(1 * RC5_UNIT)
31#define RC5X_SPACE		(4 * RC5_UNIT)
32
33enum rc5_state {
34	STATE_INACTIVE,
35	STATE_BIT_START,
36	STATE_BIT_END,
37	STATE_CHECK_RC5X,
38	STATE_FINISHED,
39};
40
41/**
42 * ir_rc5_decode() - Decode one RC-5 pulse or space
43 * @dev:	the struct rc_dev descriptor of the device
44 * @ev:		the struct ir_raw_event descriptor of the pulse/space
45 *
46 * This function returns -EINVAL if the pulse violates the state machine
47 */
48static int ir_rc5_decode(struct rc_dev *dev, struct ir_raw_event ev)
49{
50	struct rc5_dec *data = &dev->raw->rc5;
51	u8 toggle;
52	u32 scancode;
53
54        if (!(dev->raw->enabled_protocols & RC_TYPE_RC5))
55                return 0;
56
57	if (!is_timing_event(ev)) {
58		if (ev.reset)
59			data->state = STATE_INACTIVE;
60		return 0;
61	}
62
63	if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
64		goto out;
65
66again:
67	IR_dprintk(2, "RC5(x) decode started at state %i (%uus %s)\n",
68		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
69
70	if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
71		return 0;
72
73	switch (data->state) {
74
75	case STATE_INACTIVE:
76		if (!ev.pulse)
77			break;
78
79		data->state = STATE_BIT_START;
80		data->count = 1;
81		/* We just need enough bits to get to STATE_CHECK_RC5X */
82		data->wanted_bits = RC5X_NBITS;
83		decrease_duration(&ev, RC5_BIT_START);
84		goto again;
85
86	case STATE_BIT_START:
87		if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2))
88			break;
89
90		data->bits <<= 1;
91		if (!ev.pulse)
92			data->bits |= 1;
93		data->count++;
94		data->state = STATE_BIT_END;
95		return 0;
96
97	case STATE_BIT_END:
98		if (!is_transition(&ev, &dev->raw->prev_ev))
99			break;
100
101		if (data->count == data->wanted_bits)
102			data->state = STATE_FINISHED;
103		else if (data->count == CHECK_RC5X_NBITS)
104			data->state = STATE_CHECK_RC5X;
105		else
106			data->state = STATE_BIT_START;
107
108		decrease_duration(&ev, RC5_BIT_END);
109		goto again;
110
111	case STATE_CHECK_RC5X:
112		if (!ev.pulse && geq_margin(ev.duration, RC5X_SPACE, RC5_UNIT / 2)) {
113			/* RC5X */
114			data->wanted_bits = RC5X_NBITS;
115			decrease_duration(&ev, RC5X_SPACE);
116		} else {
117			/* RC5 */
118			data->wanted_bits = RC5_NBITS;
119		}
120		data->state = STATE_BIT_START;
121		goto again;
122
123	case STATE_FINISHED:
124		if (ev.pulse)
125			break;
126
127		if (data->wanted_bits == RC5X_NBITS) {
128			/* RC5X */
129			u8 xdata, command, system;
130			xdata    = (data->bits & 0x0003F) >> 0;
131			command  = (data->bits & 0x00FC0) >> 6;
132			system   = (data->bits & 0x1F000) >> 12;
133			toggle   = (data->bits & 0x20000) ? 1 : 0;
134			command += (data->bits & 0x01000) ? 0 : 0x40;
135			scancode = system << 16 | command << 8 | xdata;
136
137			IR_dprintk(1, "RC5X scancode 0x%06x (toggle: %u)\n",
138				   scancode, toggle);
139
140		} else {
141			/* RC5 */
142			u8 command, system;
143			command  = (data->bits & 0x0003F) >> 0;
144			system   = (data->bits & 0x007C0) >> 6;
145			toggle   = (data->bits & 0x00800) ? 1 : 0;
146			command += (data->bits & 0x01000) ? 0 : 0x40;
147			scancode = system << 8 | command;
148
149			IR_dprintk(1, "RC5 scancode 0x%04x (toggle: %u)\n",
150				   scancode, toggle);
151		}
152
153		rc_keydown(dev, scancode, toggle);
154		data->state = STATE_INACTIVE;
155		return 0;
156	}
157
158out:
159	IR_dprintk(1, "RC5(x) decode failed at state %i (%uus %s)\n",
160		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
161	data->state = STATE_INACTIVE;
162	return -EINVAL;
163}
164
165static struct ir_raw_handler rc5_handler = {
166	.protocols	= RC_TYPE_RC5,
167	.decode		= ir_rc5_decode,
168};
169
170static int __init ir_rc5_decode_init(void)
171{
172	ir_raw_handler_register(&rc5_handler);
173
174	printk(KERN_INFO "IR RC5(x) protocol handler initialized\n");
175	return 0;
176}
177
178static void __exit ir_rc5_decode_exit(void)
179{
180	ir_raw_handler_unregister(&rc5_handler);
181}
182
183module_init(ir_rc5_decode_init);
184module_exit(ir_rc5_decode_exit);
185
186MODULE_LICENSE("GPL");
187MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
188MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
189MODULE_DESCRIPTION("RC5(x) IR protocol decoder");
190