1 /* ir-rc6-decoder.c - A decoder for the RC6 IR protocol
2  *
3  * Copyright (C) 2010 by David Härdeman <david@hardeman.nu>
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 #include "rc-core-priv.h"
16 #include <linux/module.h>
17 
18 /*
19  * This decoder currently supports:
20  * RC6-0-16	(standard toggle bit in header)
21  * RC6-6A-20	(no toggle bit)
22  * RC6-6A-24	(no toggle bit)
23  * RC6-6A-32	(MCE version with toggle bit in body)
24  */
25 
26 #define RC6_UNIT		444444	/* nanosecs */
27 #define RC6_HEADER_NBITS	4	/* not including toggle bit */
28 #define RC6_0_NBITS		16
29 #define RC6_6A_32_NBITS		32
30 #define RC6_6A_NBITS		128	/* Variable 8..128 */
31 #define RC6_PREFIX_PULSE	(6 * RC6_UNIT)
32 #define RC6_PREFIX_SPACE	(2 * RC6_UNIT)
33 #define RC6_BIT_START		(1 * RC6_UNIT)
34 #define RC6_BIT_END		(1 * RC6_UNIT)
35 #define RC6_TOGGLE_START	(2 * RC6_UNIT)
36 #define RC6_TOGGLE_END		(2 * RC6_UNIT)
37 #define RC6_SUFFIX_SPACE	(6 * RC6_UNIT)
38 #define RC6_MODE_MASK		0x07	/* for the header bits */
39 #define RC6_STARTBIT_MASK	0x08	/* for the header bits */
40 #define RC6_6A_MCE_TOGGLE_MASK	0x8000	/* for the body bits */
41 #define RC6_6A_LCC_MASK		0xffff0000 /* RC6-6A-32 long customer code mask */
42 #define RC6_6A_MCE_CC		0x800f0000 /* MCE customer code */
43 #ifndef CHAR_BIT
44 #define CHAR_BIT 8	/* Normally in <limits.h> */
45 #endif
46 
47 enum rc6_mode {
48 	RC6_MODE_0,
49 	RC6_MODE_6A,
50 	RC6_MODE_UNKNOWN,
51 };
52 
53 enum rc6_state {
54 	STATE_INACTIVE,
55 	STATE_PREFIX_SPACE,
56 	STATE_HEADER_BIT_START,
57 	STATE_HEADER_BIT_END,
58 	STATE_TOGGLE_START,
59 	STATE_TOGGLE_END,
60 	STATE_BODY_BIT_START,
61 	STATE_BODY_BIT_END,
62 	STATE_FINISHED,
63 };
64 
65 static enum rc6_mode rc6_mode(struct rc6_dec *data)
66 {
67 	switch (data->header & RC6_MODE_MASK) {
68 	case 0:
69 		return RC6_MODE_0;
70 	case 6:
71 		if (!data->toggle)
72 			return RC6_MODE_6A;
73 		/* fall through */
74 	default:
75 		return RC6_MODE_UNKNOWN;
76 	}
77 }
78 
79 /**
80  * ir_rc6_decode() - Decode one RC6 pulse or space
81  * @dev:	the struct rc_dev descriptor of the device
82  * @ev:		the struct ir_raw_event descriptor of the pulse/space
83  *
84  * This function returns -EINVAL if the pulse violates the state machine
85  */
86 static int ir_rc6_decode(struct rc_dev *dev, struct ir_raw_event ev)
87 {
88 	struct rc6_dec *data = &dev->raw->rc6;
89 	u32 scancode;
90 	u8 toggle;
91 	enum rc_type protocol;
92 
93 	if (!is_timing_event(ev)) {
94 		if (ev.reset)
95 			data->state = STATE_INACTIVE;
96 		return 0;
97 	}
98 
99 	if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
100 		goto out;
101 
102 again:
103 	IR_dprintk(2, "RC6 decode started at state %i (%uus %s)\n",
104 		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
105 
106 	if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
107 		return 0;
108 
109 	switch (data->state) {
110 
111 	case STATE_INACTIVE:
112 		if (!ev.pulse)
113 			break;
114 
115 		/* Note: larger margin on first pulse since each RC6_UNIT
116 		   is quite short and some hardware takes some time to
117 		   adjust to the signal */
118 		if (!eq_margin(ev.duration, RC6_PREFIX_PULSE, RC6_UNIT))
119 			break;
120 
121 		data->state = STATE_PREFIX_SPACE;
122 		data->count = 0;
123 		return 0;
124 
125 	case STATE_PREFIX_SPACE:
126 		if (ev.pulse)
127 			break;
128 
129 		if (!eq_margin(ev.duration, RC6_PREFIX_SPACE, RC6_UNIT / 2))
130 			break;
131 
132 		data->state = STATE_HEADER_BIT_START;
133 		data->header = 0;
134 		return 0;
135 
136 	case STATE_HEADER_BIT_START:
137 		if (!eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2))
138 			break;
139 
140 		data->header <<= 1;
141 		if (ev.pulse)
142 			data->header |= 1;
143 		data->count++;
144 		data->state = STATE_HEADER_BIT_END;
145 		return 0;
146 
147 	case STATE_HEADER_BIT_END:
148 		if (!is_transition(&ev, &dev->raw->prev_ev))
149 			break;
150 
151 		if (data->count == RC6_HEADER_NBITS)
152 			data->state = STATE_TOGGLE_START;
153 		else
154 			data->state = STATE_HEADER_BIT_START;
155 
156 		decrease_duration(&ev, RC6_BIT_END);
157 		goto again;
158 
159 	case STATE_TOGGLE_START:
160 		if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
161 			break;
162 
163 		data->toggle = ev.pulse;
164 		data->state = STATE_TOGGLE_END;
165 		return 0;
166 
167 	case STATE_TOGGLE_END:
168 		if (!is_transition(&ev, &dev->raw->prev_ev) ||
169 		    !geq_margin(ev.duration, RC6_TOGGLE_END, RC6_UNIT / 2))
170 			break;
171 
172 		if (!(data->header & RC6_STARTBIT_MASK)) {
173 			IR_dprintk(1, "RC6 invalid start bit\n");
174 			break;
175 		}
176 
177 		data->state = STATE_BODY_BIT_START;
178 		decrease_duration(&ev, RC6_TOGGLE_END);
179 		data->count = 0;
180 		data->body = 0;
181 
182 		switch (rc6_mode(data)) {
183 		case RC6_MODE_0:
184 			data->wanted_bits = RC6_0_NBITS;
185 			break;
186 		case RC6_MODE_6A:
187 			data->wanted_bits = RC6_6A_NBITS;
188 			break;
189 		default:
190 			IR_dprintk(1, "RC6 unknown mode\n");
191 			goto out;
192 		}
193 		goto again;
194 
195 	case STATE_BODY_BIT_START:
196 		if (eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2)) {
197 			/* Discard LSB's that won't fit in data->body */
198 			if (data->count++ < CHAR_BIT * sizeof data->body) {
199 				data->body <<= 1;
200 				if (ev.pulse)
201 					data->body |= 1;
202 			}
203 			data->state = STATE_BODY_BIT_END;
204 			return 0;
205 		} else if (RC6_MODE_6A == rc6_mode(data) && !ev.pulse &&
206 				geq_margin(ev.duration, RC6_SUFFIX_SPACE, RC6_UNIT / 2)) {
207 			data->state = STATE_FINISHED;
208 			goto again;
209 		}
210 		break;
211 
212 	case STATE_BODY_BIT_END:
213 		if (!is_transition(&ev, &dev->raw->prev_ev))
214 			break;
215 
216 		if (data->count == data->wanted_bits)
217 			data->state = STATE_FINISHED;
218 		else
219 			data->state = STATE_BODY_BIT_START;
220 
221 		decrease_duration(&ev, RC6_BIT_END);
222 		goto again;
223 
224 	case STATE_FINISHED:
225 		if (ev.pulse)
226 			break;
227 
228 		switch (rc6_mode(data)) {
229 		case RC6_MODE_0:
230 			scancode = data->body;
231 			toggle = data->toggle;
232 			protocol = RC_TYPE_RC6_0;
233 			IR_dprintk(1, "RC6(0) scancode 0x%04x (toggle: %u)\n",
234 				   scancode, toggle);
235 			break;
236 
237 		case RC6_MODE_6A:
238 			if (data->count > CHAR_BIT * sizeof data->body) {
239 				IR_dprintk(1, "RC6 too many (%u) data bits\n",
240 					data->count);
241 				goto out;
242 			}
243 
244 			scancode = data->body;
245 			switch (data->count) {
246 			case 20:
247 				protocol = RC_TYPE_RC6_6A_20;
248 				toggle = 0;
249 				break;
250 			case 24:
251 				protocol = RC_BIT_RC6_6A_24;
252 				toggle = 0;
253 				break;
254 			case 32:
255 				if ((scancode & RC6_6A_LCC_MASK) == RC6_6A_MCE_CC) {
256 					protocol = RC_TYPE_RC6_MCE;
257 					toggle = !!(scancode & RC6_6A_MCE_TOGGLE_MASK);
258 					scancode &= ~RC6_6A_MCE_TOGGLE_MASK;
259 				} else {
260 					protocol = RC_BIT_RC6_6A_32;
261 					toggle = 0;
262 				}
263 				break;
264 			default:
265 				IR_dprintk(1, "RC6(6A) unsupported length\n");
266 				goto out;
267 			}
268 
269 			IR_dprintk(1, "RC6(6A) proto 0x%04x, scancode 0x%08x (toggle: %u)\n",
270 				   protocol, scancode, toggle);
271 			break;
272 		default:
273 			IR_dprintk(1, "RC6 unknown mode\n");
274 			goto out;
275 		}
276 
277 		rc_keydown(dev, protocol, scancode, toggle);
278 		data->state = STATE_INACTIVE;
279 		return 0;
280 	}
281 
282 out:
283 	IR_dprintk(1, "RC6 decode failed at state %i (%uus %s)\n",
284 		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
285 	data->state = STATE_INACTIVE;
286 	return -EINVAL;
287 }
288 
289 static struct ir_raw_handler rc6_handler = {
290 	.protocols	= RC_BIT_RC6_0 | RC_BIT_RC6_6A_20 |
291 			  RC_BIT_RC6_6A_24 | RC_BIT_RC6_6A_32 |
292 			  RC_BIT_RC6_MCE,
293 	.decode		= ir_rc6_decode,
294 };
295 
296 static int __init ir_rc6_decode_init(void)
297 {
298 	ir_raw_handler_register(&rc6_handler);
299 
300 	printk(KERN_INFO "IR RC6 protocol handler initialized\n");
301 	return 0;
302 }
303 
304 static void __exit ir_rc6_decode_exit(void)
305 {
306 	ir_raw_handler_unregister(&rc6_handler);
307 }
308 
309 module_init(ir_rc6_decode_init);
310 module_exit(ir_rc6_decode_exit);
311 
312 MODULE_LICENSE("GPL");
313 MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
314 MODULE_DESCRIPTION("RC6 IR protocol decoder");
315