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_proto 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 	dev_dbg(&dev->dev, "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 (data->count == RC6_HEADER_NBITS)
149 			data->state = STATE_TOGGLE_START;
150 		else
151 			data->state = STATE_HEADER_BIT_START;
152 
153 		decrease_duration(&ev, RC6_BIT_END);
154 		goto again;
155 
156 	case STATE_TOGGLE_START:
157 		if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
158 			break;
159 
160 		data->toggle = ev.pulse;
161 		data->state = STATE_TOGGLE_END;
162 		return 0;
163 
164 	case STATE_TOGGLE_END:
165 		if (!(data->header & RC6_STARTBIT_MASK)) {
166 			dev_dbg(&dev->dev, "RC6 invalid start bit\n");
167 			break;
168 		}
169 
170 		data->state = STATE_BODY_BIT_START;
171 		decrease_duration(&ev, RC6_TOGGLE_END);
172 		data->count = 0;
173 		data->body = 0;
174 
175 		switch (rc6_mode(data)) {
176 		case RC6_MODE_0:
177 			data->wanted_bits = RC6_0_NBITS;
178 			break;
179 		case RC6_MODE_6A:
180 			data->wanted_bits = RC6_6A_NBITS;
181 			break;
182 		default:
183 			dev_dbg(&dev->dev, "RC6 unknown mode\n");
184 			goto out;
185 		}
186 		goto again;
187 
188 	case STATE_BODY_BIT_START:
189 		if (eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2)) {
190 			/* Discard LSB's that won't fit in data->body */
191 			if (data->count++ < CHAR_BIT * sizeof data->body) {
192 				data->body <<= 1;
193 				if (ev.pulse)
194 					data->body |= 1;
195 			}
196 			data->state = STATE_BODY_BIT_END;
197 			return 0;
198 		} else if (RC6_MODE_6A == rc6_mode(data) && !ev.pulse &&
199 				geq_margin(ev.duration, RC6_SUFFIX_SPACE, RC6_UNIT / 2)) {
200 			data->state = STATE_FINISHED;
201 			goto again;
202 		}
203 		break;
204 
205 	case STATE_BODY_BIT_END:
206 		if (data->count == data->wanted_bits)
207 			data->state = STATE_FINISHED;
208 		else
209 			data->state = STATE_BODY_BIT_START;
210 
211 		decrease_duration(&ev, RC6_BIT_END);
212 		goto again;
213 
214 	case STATE_FINISHED:
215 		if (ev.pulse)
216 			break;
217 
218 		switch (rc6_mode(data)) {
219 		case RC6_MODE_0:
220 			scancode = data->body;
221 			toggle = data->toggle;
222 			protocol = RC_PROTO_RC6_0;
223 			dev_dbg(&dev->dev, "RC6(0) scancode 0x%04x (toggle: %u)\n",
224 				scancode, toggle);
225 			break;
226 
227 		case RC6_MODE_6A:
228 			if (data->count > CHAR_BIT * sizeof data->body) {
229 				dev_dbg(&dev->dev, "RC6 too many (%u) data bits\n",
230 					data->count);
231 				goto out;
232 			}
233 
234 			scancode = data->body;
235 			switch (data->count) {
236 			case 20:
237 				protocol = RC_PROTO_RC6_6A_20;
238 				toggle = 0;
239 				break;
240 			case 24:
241 				protocol = RC_PROTO_RC6_6A_24;
242 				toggle = 0;
243 				break;
244 			case 32:
245 				if ((scancode & RC6_6A_LCC_MASK) == RC6_6A_MCE_CC) {
246 					protocol = RC_PROTO_RC6_MCE;
247 					toggle = !!(scancode & RC6_6A_MCE_TOGGLE_MASK);
248 					scancode &= ~RC6_6A_MCE_TOGGLE_MASK;
249 				} else {
250 					protocol = RC_PROTO_RC6_6A_32;
251 					toggle = 0;
252 				}
253 				break;
254 			default:
255 				dev_dbg(&dev->dev, "RC6(6A) unsupported length\n");
256 				goto out;
257 			}
258 
259 			dev_dbg(&dev->dev, "RC6(6A) proto 0x%04x, scancode 0x%08x (toggle: %u)\n",
260 				protocol, scancode, toggle);
261 			break;
262 		default:
263 			dev_dbg(&dev->dev, "RC6 unknown mode\n");
264 			goto out;
265 		}
266 
267 		rc_keydown(dev, protocol, scancode, toggle);
268 		data->state = STATE_INACTIVE;
269 		return 0;
270 	}
271 
272 out:
273 	dev_dbg(&dev->dev, "RC6 decode failed at state %i (%uus %s)\n",
274 		data->state, TO_US(ev.duration), TO_STR(ev.pulse));
275 	data->state = STATE_INACTIVE;
276 	return -EINVAL;
277 }
278 
279 static const struct ir_raw_timings_manchester ir_rc6_timings[4] = {
280 	{
281 		.leader_pulse		= RC6_PREFIX_PULSE,
282 		.leader_space		= RC6_PREFIX_SPACE,
283 		.clock			= RC6_UNIT,
284 		.invert			= 1,
285 	},
286 	{
287 		.clock			= RC6_UNIT * 2,
288 		.invert			= 1,
289 	},
290 	{
291 		.clock			= RC6_UNIT,
292 		.invert			= 1,
293 		.trailer_space		= RC6_SUFFIX_SPACE,
294 	},
295 };
296 
297 /**
298  * ir_rc6_encode() - Encode a scancode as a stream of raw events
299  *
300  * @protocol:	protocol to encode
301  * @scancode:	scancode to encode
302  * @events:	array of raw ir events to write into
303  * @max:	maximum size of @events
304  *
305  * Returns:	The number of events written.
306  *		-ENOBUFS if there isn't enough space in the array to fit the
307  *		encoding. In this case all @max events will have been written.
308  *		-EINVAL if the scancode is ambiguous or invalid.
309  */
310 static int ir_rc6_encode(enum rc_proto protocol, u32 scancode,
311 			 struct ir_raw_event *events, unsigned int max)
312 {
313 	int ret;
314 	struct ir_raw_event *e = events;
315 
316 	if (protocol == RC_PROTO_RC6_0) {
317 		/* Modulate the header (Start Bit & Mode-0) */
318 		ret = ir_raw_gen_manchester(&e, max - (e - events),
319 					    &ir_rc6_timings[0],
320 					    RC6_HEADER_NBITS, (1 << 3));
321 		if (ret < 0)
322 			return ret;
323 
324 		/* Modulate Trailer Bit */
325 		ret = ir_raw_gen_manchester(&e, max - (e - events),
326 					    &ir_rc6_timings[1], 1, 0);
327 		if (ret < 0)
328 			return ret;
329 
330 		/* Modulate rest of the data */
331 		ret = ir_raw_gen_manchester(&e, max - (e - events),
332 					    &ir_rc6_timings[2], RC6_0_NBITS,
333 					    scancode);
334 		if (ret < 0)
335 			return ret;
336 
337 	} else {
338 		int bits;
339 
340 		switch (protocol) {
341 		case RC_PROTO_RC6_MCE:
342 		case RC_PROTO_RC6_6A_32:
343 			bits = 32;
344 			break;
345 		case RC_PROTO_RC6_6A_24:
346 			bits = 24;
347 			break;
348 		case RC_PROTO_RC6_6A_20:
349 			bits = 20;
350 			break;
351 		default:
352 			return -EINVAL;
353 		}
354 
355 		/* Modulate the header (Start Bit & Header-version 6 */
356 		ret = ir_raw_gen_manchester(&e, max - (e - events),
357 					    &ir_rc6_timings[0],
358 					    RC6_HEADER_NBITS, (1 << 3 | 6));
359 		if (ret < 0)
360 			return ret;
361 
362 		/* Modulate Trailer Bit */
363 		ret = ir_raw_gen_manchester(&e, max - (e - events),
364 					    &ir_rc6_timings[1], 1, 0);
365 		if (ret < 0)
366 			return ret;
367 
368 		/* Modulate rest of the data */
369 		ret = ir_raw_gen_manchester(&e, max - (e - events),
370 					    &ir_rc6_timings[2],
371 					    bits,
372 					    scancode);
373 		if (ret < 0)
374 			return ret;
375 	}
376 
377 	return e - events;
378 }
379 
380 static struct ir_raw_handler rc6_handler = {
381 	.protocols	= RC_PROTO_BIT_RC6_0 | RC_PROTO_BIT_RC6_6A_20 |
382 			  RC_PROTO_BIT_RC6_6A_24 | RC_PROTO_BIT_RC6_6A_32 |
383 			  RC_PROTO_BIT_RC6_MCE,
384 	.decode		= ir_rc6_decode,
385 	.encode		= ir_rc6_encode,
386 	.carrier	= 36000,
387 	.min_timeout	= RC6_SUFFIX_SPACE,
388 };
389 
390 static int __init ir_rc6_decode_init(void)
391 {
392 	ir_raw_handler_register(&rc6_handler);
393 
394 	printk(KERN_INFO "IR RC6 protocol handler initialized\n");
395 	return 0;
396 }
397 
398 static void __exit ir_rc6_decode_exit(void)
399 {
400 	ir_raw_handler_unregister(&rc6_handler);
401 }
402 
403 module_init(ir_rc6_decode_init);
404 module_exit(ir_rc6_decode_exit);
405 
406 MODULE_LICENSE("GPL");
407 MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
408 MODULE_DESCRIPTION("RC6 IR protocol decoder");
409