1 /* ir-rc5-decoder.c - decoder for RC5(x) and StreamZap protocols
2  *
3  * Copyright (C) 2010 by Mauro Carvalho Chehab
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 decoder handles the 14 bit RC5 protocol, 15 bit "StreamZap" protocol
18  * and 20 bit RC5x protocol.
19  */
20 
21 #include "rc-core-priv.h"
22 #include <linux/module.h>
23 
24 #define RC5_NBITS		14
25 #define RC5_SZ_NBITS		15
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 #define RC5_TRAILER		(10 * RC5_UNIT) /* In reality, approx 100 */
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 	enum rc_type protocol;
55 
56 	if (!(dev->enabled_protocols & (RC_BIT_RC5 | RC_BIT_RC5X | RC_BIT_RC5_SZ)))
57 		return 0;
58 
59 	if (!is_timing_event(ev)) {
60 		if (ev.reset)
61 			data->state = STATE_INACTIVE;
62 		return 0;
63 	}
64 
65 	if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
66 		goto out;
67 
68 again:
69 	IR_dprintk(2, "RC5(x/sz) decode started at state %i (%uus %s)\n",
70 		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
71 
72 	if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
73 		return 0;
74 
75 	switch (data->state) {
76 
77 	case STATE_INACTIVE:
78 		if (!ev.pulse)
79 			break;
80 
81 		data->state = STATE_BIT_START;
82 		data->count = 1;
83 		decrease_duration(&ev, RC5_BIT_START);
84 		goto again;
85 
86 	case STATE_BIT_START:
87 		if (!ev.pulse && geq_margin(ev.duration, RC5_TRAILER, RC5_UNIT / 2)) {
88 			data->state = STATE_FINISHED;
89 			goto again;
90 		}
91 
92 		if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2))
93 			break;
94 
95 		data->bits <<= 1;
96 		if (!ev.pulse)
97 			data->bits |= 1;
98 		data->count++;
99 		data->state = STATE_BIT_END;
100 		return 0;
101 
102 	case STATE_BIT_END:
103 		if (!is_transition(&ev, &dev->raw->prev_ev))
104 			break;
105 
106 		if (data->count == CHECK_RC5X_NBITS)
107 			data->state = STATE_CHECK_RC5X;
108 		else
109 			data->state = STATE_BIT_START;
110 
111 		decrease_duration(&ev, RC5_BIT_END);
112 		goto again;
113 
114 	case STATE_CHECK_RC5X:
115 		if (!ev.pulse && geq_margin(ev.duration, RC5X_SPACE, RC5_UNIT / 2)) {
116 			data->is_rc5x = true;
117 			decrease_duration(&ev, RC5X_SPACE);
118 		} else
119 			data->is_rc5x = false;
120 		data->state = STATE_BIT_START;
121 		goto again;
122 
123 	case STATE_FINISHED:
124 		if (ev.pulse)
125 			break;
126 
127 		if (data->is_rc5x && data->count == RC5X_NBITS) {
128 			/* RC5X */
129 			u8 xdata, command, system;
130 			if (!(dev->enabled_protocols & RC_BIT_RC5X)) {
131 				data->state = STATE_INACTIVE;
132 				return 0;
133 			}
134 			xdata    = (data->bits & 0x0003F) >> 0;
135 			command  = (data->bits & 0x00FC0) >> 6;
136 			system   = (data->bits & 0x1F000) >> 12;
137 			toggle   = (data->bits & 0x20000) ? 1 : 0;
138 			command += (data->bits & 0x01000) ? 0 : 0x40;
139 			scancode = system << 16 | command << 8 | xdata;
140 			protocol = RC_TYPE_RC5X;
141 
142 		} else if (!data->is_rc5x && data->count == RC5_NBITS) {
143 			/* RC5 */
144 			u8 command, system;
145 			if (!(dev->enabled_protocols & RC_BIT_RC5)) {
146 				data->state = STATE_INACTIVE;
147 				return 0;
148 			}
149 			command  = (data->bits & 0x0003F) >> 0;
150 			system   = (data->bits & 0x007C0) >> 6;
151 			toggle   = (data->bits & 0x00800) ? 1 : 0;
152 			command += (data->bits & 0x01000) ? 0 : 0x40;
153 			scancode = system << 8 | command;
154 			protocol = RC_TYPE_RC5;
155 
156 		} else if (!data->is_rc5x && data->count == RC5_SZ_NBITS) {
157 			/* RC5 StreamZap */
158 			u8 command, system;
159 			if (!(dev->enabled_protocols & RC_BIT_RC5_SZ)) {
160 				data->state = STATE_INACTIVE;
161 				return 0;
162 			}
163 			command  = (data->bits & 0x0003F) >> 0;
164 			system   = (data->bits & 0x02FC0) >> 6;
165 			toggle   = (data->bits & 0x01000) ? 1 : 0;
166 			scancode = system << 6 | command;
167 			protocol = RC_TYPE_RC5_SZ;
168 
169 		} else
170 			break;
171 
172 		IR_dprintk(1, "RC5(x/sz) scancode 0x%06x (p: %u, t: %u)\n",
173 			   scancode, protocol, toggle);
174 
175 		rc_keydown(dev, protocol, scancode, toggle);
176 		data->state = STATE_INACTIVE;
177 		return 0;
178 	}
179 
180 out:
181 	IR_dprintk(1, "RC5(x/sz) decode failed at state %i count %d (%uus %s)\n",
182 		   data->state, data->count, TO_US(ev.duration), TO_STR(ev.pulse));
183 	data->state = STATE_INACTIVE;
184 	return -EINVAL;
185 }
186 
187 static struct ir_raw_handler rc5_handler = {
188 	.protocols	= RC_BIT_RC5 | RC_BIT_RC5X | RC_BIT_RC5_SZ,
189 	.decode		= ir_rc5_decode,
190 };
191 
192 static int __init ir_rc5_decode_init(void)
193 {
194 	ir_raw_handler_register(&rc5_handler);
195 
196 	printk(KERN_INFO "IR RC5(x/sz) protocol handler initialized\n");
197 	return 0;
198 }
199 
200 static void __exit ir_rc5_decode_exit(void)
201 {
202 	ir_raw_handler_unregister(&rc5_handler);
203 }
204 
205 module_init(ir_rc5_decode_init);
206 module_exit(ir_rc5_decode_exit);
207 
208 MODULE_LICENSE("GPL");
209 MODULE_AUTHOR("Mauro Carvalho Chehab and Jarod Wilson");
210 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
211 MODULE_DESCRIPTION("RC5(x/sz) IR protocol decoder");
212