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 #include <linux/module.h>
25 
26 #define RC5_NBITS		14
27 #define RC5X_NBITS		20
28 #define CHECK_RC5X_NBITS	8
29 #define RC5_UNIT		888888 /* ns */
30 #define RC5_BIT_START		(1 * RC5_UNIT)
31 #define RC5_BIT_END		(1 * RC5_UNIT)
32 #define RC5X_SPACE		(4 * RC5_UNIT)
33 
34 enum rc5_state {
35 	STATE_INACTIVE,
36 	STATE_BIT_START,
37 	STATE_BIT_END,
38 	STATE_CHECK_RC5X,
39 	STATE_FINISHED,
40 };
41 
42 /**
43  * ir_rc5_decode() - Decode one RC-5 pulse or space
44  * @dev:	the struct rc_dev descriptor of the device
45  * @ev:		the struct ir_raw_event descriptor of the pulse/space
46  *
47  * This function returns -EINVAL if the pulse violates the state machine
48  */
49 static int ir_rc5_decode(struct rc_dev *dev, struct ir_raw_event ev)
50 {
51 	struct rc5_dec *data = &dev->raw->rc5;
52 	u8 toggle;
53 	u32 scancode;
54 
55 	if (!(dev->enabled_protocols & (RC_BIT_RC5 | RC_BIT_RC5X)))
56 		return 0;
57 
58 	if (!is_timing_event(ev)) {
59 		if (ev.reset)
60 			data->state = STATE_INACTIVE;
61 		return 0;
62 	}
63 
64 	if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
65 		goto out;
66 
67 again:
68 	IR_dprintk(2, "RC5(x) decode started at state %i (%uus %s)\n",
69 		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
70 
71 	if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
72 		return 0;
73 
74 	switch (data->state) {
75 
76 	case STATE_INACTIVE:
77 		if (!ev.pulse)
78 			break;
79 
80 		data->state = STATE_BIT_START;
81 		data->count = 1;
82 		/* We just need enough bits to get to STATE_CHECK_RC5X */
83 		data->wanted_bits = RC5X_NBITS;
84 		decrease_duration(&ev, RC5_BIT_START);
85 		goto again;
86 
87 	case STATE_BIT_START:
88 		if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2))
89 			break;
90 
91 		data->bits <<= 1;
92 		if (!ev.pulse)
93 			data->bits |= 1;
94 		data->count++;
95 		data->state = STATE_BIT_END;
96 		return 0;
97 
98 	case STATE_BIT_END:
99 		if (!is_transition(&ev, &dev->raw->prev_ev))
100 			break;
101 
102 		if (data->count == data->wanted_bits)
103 			data->state = STATE_FINISHED;
104 		else if (data->count == CHECK_RC5X_NBITS)
105 			data->state = STATE_CHECK_RC5X;
106 		else
107 			data->state = STATE_BIT_START;
108 
109 		decrease_duration(&ev, RC5_BIT_END);
110 		goto again;
111 
112 	case STATE_CHECK_RC5X:
113 		if (!ev.pulse && geq_margin(ev.duration, RC5X_SPACE, RC5_UNIT / 2)) {
114 			/* RC5X */
115 			data->wanted_bits = RC5X_NBITS;
116 			decrease_duration(&ev, RC5X_SPACE);
117 		} else {
118 			/* RC5 */
119 			data->wanted_bits = RC5_NBITS;
120 		}
121 		data->state = STATE_BIT_START;
122 		goto again;
123 
124 	case STATE_FINISHED:
125 		if (ev.pulse)
126 			break;
127 
128 		if (data->wanted_bits == RC5X_NBITS) {
129 			/* RC5X */
130 			u8 xdata, command, system;
131 			if (!(dev->enabled_protocols & RC_BIT_RC5X)) {
132 				data->state = STATE_INACTIVE;
133 				return 0;
134 			}
135 			xdata    = (data->bits & 0x0003F) >> 0;
136 			command  = (data->bits & 0x00FC0) >> 6;
137 			system   = (data->bits & 0x1F000) >> 12;
138 			toggle   = (data->bits & 0x20000) ? 1 : 0;
139 			command += (data->bits & 0x01000) ? 0 : 0x40;
140 			scancode = system << 16 | command << 8 | xdata;
141 
142 			IR_dprintk(1, "RC5X scancode 0x%06x (toggle: %u)\n",
143 				   scancode, toggle);
144 
145 		} else {
146 			/* RC5 */
147 			u8 command, system;
148 			if (!(dev->enabled_protocols & RC_BIT_RC5)) {
149 				data->state = STATE_INACTIVE;
150 				return 0;
151 			}
152 			command  = (data->bits & 0x0003F) >> 0;
153 			system   = (data->bits & 0x007C0) >> 6;
154 			toggle   = (data->bits & 0x00800) ? 1 : 0;
155 			command += (data->bits & 0x01000) ? 0 : 0x40;
156 			scancode = system << 8 | command;
157 
158 			IR_dprintk(1, "RC5 scancode 0x%04x (toggle: %u)\n",
159 				   scancode, toggle);
160 		}
161 
162 		rc_keydown(dev, scancode, toggle);
163 		data->state = STATE_INACTIVE;
164 		return 0;
165 	}
166 
167 out:
168 	IR_dprintk(1, "RC5(x) decode failed at state %i (%uus %s)\n",
169 		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
170 	data->state = STATE_INACTIVE;
171 	return -EINVAL;
172 }
173 
174 static struct ir_raw_handler rc5_handler = {
175 	.protocols	= RC_BIT_RC5 | RC_BIT_RC5X,
176 	.decode		= ir_rc5_decode,
177 };
178 
179 static int __init ir_rc5_decode_init(void)
180 {
181 	ir_raw_handler_register(&rc5_handler);
182 
183 	printk(KERN_INFO "IR RC5(x) protocol handler initialized\n");
184 	return 0;
185 }
186 
187 static void __exit ir_rc5_decode_exit(void)
188 {
189 	ir_raw_handler_unregister(&rc5_handler);
190 }
191 
192 module_init(ir_rc5_decode_init);
193 module_exit(ir_rc5_decode_exit);
194 
195 MODULE_LICENSE("GPL");
196 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
197 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
198 MODULE_DESCRIPTION("RC5(x) IR protocol decoder");
199