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 #define RC6_6A_KATHREIN_CC	0x80460000 /* Kathrein RCU-676 customer code */
44 #ifndef CHAR_BIT
45 #define CHAR_BIT 8	/* Normally in <limits.h> */
46 #endif
47 
48 enum rc6_mode {
49 	RC6_MODE_0,
50 	RC6_MODE_6A,
51 	RC6_MODE_UNKNOWN,
52 };
53 
54 enum rc6_state {
55 	STATE_INACTIVE,
56 	STATE_PREFIX_SPACE,
57 	STATE_HEADER_BIT_START,
58 	STATE_HEADER_BIT_END,
59 	STATE_TOGGLE_START,
60 	STATE_TOGGLE_END,
61 	STATE_BODY_BIT_START,
62 	STATE_BODY_BIT_END,
63 	STATE_FINISHED,
64 };
65 
66 static enum rc6_mode rc6_mode(struct rc6_dec *data)
67 {
68 	switch (data->header & RC6_MODE_MASK) {
69 	case 0:
70 		return RC6_MODE_0;
71 	case 6:
72 		if (!data->toggle)
73 			return RC6_MODE_6A;
74 		/* fall through */
75 	default:
76 		return RC6_MODE_UNKNOWN;
77 	}
78 }
79 
80 /**
81  * ir_rc6_decode() - Decode one RC6 pulse or space
82  * @dev:	the struct rc_dev descriptor of the device
83  * @ev:		the struct ir_raw_event descriptor of the pulse/space
84  *
85  * This function returns -EINVAL if the pulse violates the state machine
86  */
87 static int ir_rc6_decode(struct rc_dev *dev, struct ir_raw_event ev)
88 {
89 	struct rc6_dec *data = &dev->raw->rc6;
90 	u32 scancode;
91 	u8 toggle;
92 	enum rc_proto protocol;
93 
94 	if (!is_timing_event(ev)) {
95 		if (ev.reset)
96 			data->state = STATE_INACTIVE;
97 		return 0;
98 	}
99 
100 	if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
101 		goto out;
102 
103 again:
104 	dev_dbg(&dev->dev, "RC6 decode started at state %i (%uus %s)\n",
105 		data->state, TO_US(ev.duration), TO_STR(ev.pulse));
106 
107 	if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
108 		return 0;
109 
110 	switch (data->state) {
111 
112 	case STATE_INACTIVE:
113 		if (!ev.pulse)
114 			break;
115 
116 		/* Note: larger margin on first pulse since each RC6_UNIT
117 		   is quite short and some hardware takes some time to
118 		   adjust to the signal */
119 		if (!eq_margin(ev.duration, RC6_PREFIX_PULSE, RC6_UNIT))
120 			break;
121 
122 		data->state = STATE_PREFIX_SPACE;
123 		data->count = 0;
124 		return 0;
125 
126 	case STATE_PREFIX_SPACE:
127 		if (ev.pulse)
128 			break;
129 
130 		if (!eq_margin(ev.duration, RC6_PREFIX_SPACE, RC6_UNIT / 2))
131 			break;
132 
133 		data->state = STATE_HEADER_BIT_START;
134 		data->header = 0;
135 		return 0;
136 
137 	case STATE_HEADER_BIT_START:
138 		if (!eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2))
139 			break;
140 
141 		data->header <<= 1;
142 		if (ev.pulse)
143 			data->header |= 1;
144 		data->count++;
145 		data->state = STATE_HEADER_BIT_END;
146 		return 0;
147 
148 	case STATE_HEADER_BIT_END:
149 		if (data->count == RC6_HEADER_NBITS)
150 			data->state = STATE_TOGGLE_START;
151 		else
152 			data->state = STATE_HEADER_BIT_START;
153 
154 		decrease_duration(&ev, RC6_BIT_END);
155 		goto again;
156 
157 	case STATE_TOGGLE_START:
158 		if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
159 			break;
160 
161 		data->toggle = ev.pulse;
162 		data->state = STATE_TOGGLE_END;
163 		return 0;
164 
165 	case STATE_TOGGLE_END:
166 		if (!(data->header & RC6_STARTBIT_MASK)) {
167 			dev_dbg(&dev->dev, "RC6 invalid start bit\n");
168 			break;
169 		}
170 
171 		data->state = STATE_BODY_BIT_START;
172 		decrease_duration(&ev, RC6_TOGGLE_END);
173 		data->count = 0;
174 		data->body = 0;
175 
176 		switch (rc6_mode(data)) {
177 		case RC6_MODE_0:
178 			data->wanted_bits = RC6_0_NBITS;
179 			break;
180 		case RC6_MODE_6A:
181 			data->wanted_bits = RC6_6A_NBITS;
182 			break;
183 		default:
184 			dev_dbg(&dev->dev, "RC6 unknown mode\n");
185 			goto out;
186 		}
187 		goto again;
188 
189 	case STATE_BODY_BIT_START:
190 		if (eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2)) {
191 			/* Discard LSB's that won't fit in data->body */
192 			if (data->count++ < CHAR_BIT * sizeof data->body) {
193 				data->body <<= 1;
194 				if (ev.pulse)
195 					data->body |= 1;
196 			}
197 			data->state = STATE_BODY_BIT_END;
198 			return 0;
199 		} else if (RC6_MODE_6A == rc6_mode(data) && !ev.pulse &&
200 				geq_margin(ev.duration, RC6_SUFFIX_SPACE, RC6_UNIT / 2)) {
201 			data->state = STATE_FINISHED;
202 			goto again;
203 		}
204 		break;
205 
206 	case STATE_BODY_BIT_END:
207 		if (data->count == data->wanted_bits)
208 			data->state = STATE_FINISHED;
209 		else
210 			data->state = STATE_BODY_BIT_START;
211 
212 		decrease_duration(&ev, RC6_BIT_END);
213 		goto again;
214 
215 	case STATE_FINISHED:
216 		if (ev.pulse)
217 			break;
218 
219 		switch (rc6_mode(data)) {
220 		case RC6_MODE_0:
221 			scancode = data->body;
222 			toggle = data->toggle;
223 			protocol = RC_PROTO_RC6_0;
224 			dev_dbg(&dev->dev, "RC6(0) scancode 0x%04x (toggle: %u)\n",
225 				scancode, toggle);
226 			break;
227 
228 		case RC6_MODE_6A:
229 			if (data->count > CHAR_BIT * sizeof data->body) {
230 				dev_dbg(&dev->dev, "RC6 too many (%u) data bits\n",
231 					data->count);
232 				goto out;
233 			}
234 
235 			scancode = data->body;
236 			switch (data->count) {
237 			case 20:
238 				protocol = RC_PROTO_RC6_6A_20;
239 				toggle = 0;
240 				break;
241 			case 24:
242 				protocol = RC_PROTO_RC6_6A_24;
243 				toggle = 0;
244 				break;
245 			case 32:
246 				switch (scancode & RC6_6A_LCC_MASK) {
247 				case RC6_6A_MCE_CC:
248 				case RC6_6A_KATHREIN_CC:
249 					protocol = RC_PROTO_RC6_MCE;
250 					toggle = !!(scancode & RC6_6A_MCE_TOGGLE_MASK);
251 					scancode &= ~RC6_6A_MCE_TOGGLE_MASK;
252 					break;
253 				default:
254 					protocol = RC_PROTO_RC6_6A_32;
255 					toggle = 0;
256 					break;
257 				}
258 				break;
259 			default:
260 				dev_dbg(&dev->dev, "RC6(6A) unsupported length\n");
261 				goto out;
262 			}
263 
264 			dev_dbg(&dev->dev, "RC6(6A) proto 0x%04x, scancode 0x%08x (toggle: %u)\n",
265 				protocol, scancode, toggle);
266 			break;
267 		default:
268 			dev_dbg(&dev->dev, "RC6 unknown mode\n");
269 			goto out;
270 		}
271 
272 		rc_keydown(dev, protocol, scancode, toggle);
273 		data->state = STATE_INACTIVE;
274 		return 0;
275 	}
276 
277 out:
278 	dev_dbg(&dev->dev, "RC6 decode failed at state %i (%uus %s)\n",
279 		data->state, TO_US(ev.duration), TO_STR(ev.pulse));
280 	data->state = STATE_INACTIVE;
281 	return -EINVAL;
282 }
283 
284 static const struct ir_raw_timings_manchester ir_rc6_timings[4] = {
285 	{
286 		.leader_pulse		= RC6_PREFIX_PULSE,
287 		.leader_space		= RC6_PREFIX_SPACE,
288 		.clock			= RC6_UNIT,
289 		.invert			= 1,
290 	},
291 	{
292 		.clock			= RC6_UNIT * 2,
293 		.invert			= 1,
294 	},
295 	{
296 		.clock			= RC6_UNIT,
297 		.invert			= 1,
298 		.trailer_space		= RC6_SUFFIX_SPACE,
299 	},
300 };
301 
302 /**
303  * ir_rc6_encode() - Encode a scancode as a stream of raw events
304  *
305  * @protocol:	protocol to encode
306  * @scancode:	scancode to encode
307  * @events:	array of raw ir events to write into
308  * @max:	maximum size of @events
309  *
310  * Returns:	The number of events written.
311  *		-ENOBUFS if there isn't enough space in the array to fit the
312  *		encoding. In this case all @max events will have been written.
313  *		-EINVAL if the scancode is ambiguous or invalid.
314  */
315 static int ir_rc6_encode(enum rc_proto protocol, u32 scancode,
316 			 struct ir_raw_event *events, unsigned int max)
317 {
318 	int ret;
319 	struct ir_raw_event *e = events;
320 
321 	if (protocol == RC_PROTO_RC6_0) {
322 		/* Modulate the header (Start Bit & Mode-0) */
323 		ret = ir_raw_gen_manchester(&e, max - (e - events),
324 					    &ir_rc6_timings[0],
325 					    RC6_HEADER_NBITS, (1 << 3));
326 		if (ret < 0)
327 			return ret;
328 
329 		/* Modulate Trailer Bit */
330 		ret = ir_raw_gen_manchester(&e, max - (e - events),
331 					    &ir_rc6_timings[1], 1, 0);
332 		if (ret < 0)
333 			return ret;
334 
335 		/* Modulate rest of the data */
336 		ret = ir_raw_gen_manchester(&e, max - (e - events),
337 					    &ir_rc6_timings[2], RC6_0_NBITS,
338 					    scancode);
339 		if (ret < 0)
340 			return ret;
341 
342 	} else {
343 		int bits;
344 
345 		switch (protocol) {
346 		case RC_PROTO_RC6_MCE:
347 		case RC_PROTO_RC6_6A_32:
348 			bits = 32;
349 			break;
350 		case RC_PROTO_RC6_6A_24:
351 			bits = 24;
352 			break;
353 		case RC_PROTO_RC6_6A_20:
354 			bits = 20;
355 			break;
356 		default:
357 			return -EINVAL;
358 		}
359 
360 		/* Modulate the header (Start Bit & Header-version 6 */
361 		ret = ir_raw_gen_manchester(&e, max - (e - events),
362 					    &ir_rc6_timings[0],
363 					    RC6_HEADER_NBITS, (1 << 3 | 6));
364 		if (ret < 0)
365 			return ret;
366 
367 		/* Modulate Trailer Bit */
368 		ret = ir_raw_gen_manchester(&e, max - (e - events),
369 					    &ir_rc6_timings[1], 1, 0);
370 		if (ret < 0)
371 			return ret;
372 
373 		/* Modulate rest of the data */
374 		ret = ir_raw_gen_manchester(&e, max - (e - events),
375 					    &ir_rc6_timings[2],
376 					    bits,
377 					    scancode);
378 		if (ret < 0)
379 			return ret;
380 	}
381 
382 	return e - events;
383 }
384 
385 static struct ir_raw_handler rc6_handler = {
386 	.protocols	= RC_PROTO_BIT_RC6_0 | RC_PROTO_BIT_RC6_6A_20 |
387 			  RC_PROTO_BIT_RC6_6A_24 | RC_PROTO_BIT_RC6_6A_32 |
388 			  RC_PROTO_BIT_RC6_MCE,
389 	.decode		= ir_rc6_decode,
390 	.encode		= ir_rc6_encode,
391 	.carrier	= 36000,
392 	.min_timeout	= RC6_SUFFIX_SPACE,
393 };
394 
395 static int __init ir_rc6_decode_init(void)
396 {
397 	ir_raw_handler_register(&rc6_handler);
398 
399 	printk(KERN_INFO "IR RC6 protocol handler initialized\n");
400 	return 0;
401 }
402 
403 static void __exit ir_rc6_decode_exit(void)
404 {
405 	ir_raw_handler_unregister(&rc6_handler);
406 }
407 
408 module_init(ir_rc6_decode_init);
409 module_exit(ir_rc6_decode_exit);
410 
411 MODULE_LICENSE("GPL");
412 MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
413 MODULE_DESCRIPTION("RC6 IR protocol decoder");
414