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
33 enum 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 */
ir_rc5_decode(struct rc_dev * dev,struct ir_raw_event ev)48 static 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
66 again:
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
158 out:
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
165 static struct ir_raw_handler rc5_handler = {
166 .protocols = RC_TYPE_RC5,
167 .decode = ir_rc5_decode,
168 };
169
ir_rc5_decode_init(void)170 static 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
ir_rc5_decode_exit(void)178 static void __exit ir_rc5_decode_exit(void)
179 {
180 ir_raw_handler_unregister(&rc5_handler);
181 }
182
183 module_init(ir_rc5_decode_init);
184 module_exit(ir_rc5_decode_exit);
185
186 MODULE_LICENSE("GPL");
187 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
188 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
189 MODULE_DESCRIPTION("RC5(x) IR protocol decoder");
190