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