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 (!(dev->enabled_protocols &
94 	      (RC_BIT_RC6_0 | RC_BIT_RC6_6A_20 | RC_BIT_RC6_6A_24 |
95 	       RC_BIT_RC6_6A_32 | RC_BIT_RC6_MCE)))
96 		return 0;
97 
98 	if (!is_timing_event(ev)) {
99 		if (ev.reset)
100 			data->state = STATE_INACTIVE;
101 		return 0;
102 	}
103 
104 	if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
105 		goto out;
106 
107 again:
108 	IR_dprintk(2, "RC6 decode started at state %i (%uus %s)\n",
109 		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
110 
111 	if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
112 		return 0;
113 
114 	switch (data->state) {
115 
116 	case STATE_INACTIVE:
117 		if (!ev.pulse)
118 			break;
119 
120 		/* Note: larger margin on first pulse since each RC6_UNIT
121 		   is quite short and some hardware takes some time to
122 		   adjust to the signal */
123 		if (!eq_margin(ev.duration, RC6_PREFIX_PULSE, RC6_UNIT))
124 			break;
125 
126 		data->state = STATE_PREFIX_SPACE;
127 		data->count = 0;
128 		return 0;
129 
130 	case STATE_PREFIX_SPACE:
131 		if (ev.pulse)
132 			break;
133 
134 		if (!eq_margin(ev.duration, RC6_PREFIX_SPACE, RC6_UNIT / 2))
135 			break;
136 
137 		data->state = STATE_HEADER_BIT_START;
138 		data->header = 0;
139 		return 0;
140 
141 	case STATE_HEADER_BIT_START:
142 		if (!eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2))
143 			break;
144 
145 		data->header <<= 1;
146 		if (ev.pulse)
147 			data->header |= 1;
148 		data->count++;
149 		data->state = STATE_HEADER_BIT_END;
150 		return 0;
151 
152 	case STATE_HEADER_BIT_END:
153 		if (!is_transition(&ev, &dev->raw->prev_ev))
154 			break;
155 
156 		if (data->count == RC6_HEADER_NBITS)
157 			data->state = STATE_TOGGLE_START;
158 		else
159 			data->state = STATE_HEADER_BIT_START;
160 
161 		decrease_duration(&ev, RC6_BIT_END);
162 		goto again;
163 
164 	case STATE_TOGGLE_START:
165 		if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
166 			break;
167 
168 		data->toggle = ev.pulse;
169 		data->state = STATE_TOGGLE_END;
170 		return 0;
171 
172 	case STATE_TOGGLE_END:
173 		if (!is_transition(&ev, &dev->raw->prev_ev) ||
174 		    !geq_margin(ev.duration, RC6_TOGGLE_END, RC6_UNIT / 2))
175 			break;
176 
177 		if (!(data->header & RC6_STARTBIT_MASK)) {
178 			IR_dprintk(1, "RC6 invalid start bit\n");
179 			break;
180 		}
181 
182 		data->state = STATE_BODY_BIT_START;
183 		decrease_duration(&ev, RC6_TOGGLE_END);
184 		data->count = 0;
185 		data->body = 0;
186 
187 		switch (rc6_mode(data)) {
188 		case RC6_MODE_0:
189 			data->wanted_bits = RC6_0_NBITS;
190 			break;
191 		case RC6_MODE_6A:
192 			data->wanted_bits = RC6_6A_NBITS;
193 			break;
194 		default:
195 			IR_dprintk(1, "RC6 unknown mode\n");
196 			goto out;
197 		}
198 		goto again;
199 
200 	case STATE_BODY_BIT_START:
201 		if (eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2)) {
202 			/* Discard LSB's that won't fit in data->body */
203 			if (data->count++ < CHAR_BIT * sizeof data->body) {
204 				data->body <<= 1;
205 				if (ev.pulse)
206 					data->body |= 1;
207 			}
208 			data->state = STATE_BODY_BIT_END;
209 			return 0;
210 		} else if (RC6_MODE_6A == rc6_mode(data) && !ev.pulse &&
211 				geq_margin(ev.duration, RC6_SUFFIX_SPACE, RC6_UNIT / 2)) {
212 			data->state = STATE_FINISHED;
213 			goto again;
214 		}
215 		break;
216 
217 	case STATE_BODY_BIT_END:
218 		if (!is_transition(&ev, &dev->raw->prev_ev))
219 			break;
220 
221 		if (data->count == data->wanted_bits)
222 			data->state = STATE_FINISHED;
223 		else
224 			data->state = STATE_BODY_BIT_START;
225 
226 		decrease_duration(&ev, RC6_BIT_END);
227 		goto again;
228 
229 	case STATE_FINISHED:
230 		if (ev.pulse)
231 			break;
232 
233 		switch (rc6_mode(data)) {
234 		case RC6_MODE_0:
235 			scancode = data->body;
236 			toggle = data->toggle;
237 			protocol = RC_TYPE_RC6_0;
238 			IR_dprintk(1, "RC6(0) scancode 0x%04x (toggle: %u)\n",
239 				   scancode, toggle);
240 			break;
241 
242 		case RC6_MODE_6A:
243 			if (data->count > CHAR_BIT * sizeof data->body) {
244 				IR_dprintk(1, "RC6 too many (%u) data bits\n",
245 					data->count);
246 				goto out;
247 			}
248 
249 			scancode = data->body;
250 			switch (data->count) {
251 			case 20:
252 				protocol = RC_TYPE_RC6_6A_20;
253 				toggle = 0;
254 				break;
255 			case 24:
256 				protocol = RC_BIT_RC6_6A_24;
257 				toggle = 0;
258 				break;
259 			case 32:
260 				if ((scancode & RC6_6A_LCC_MASK) == RC6_6A_MCE_CC) {
261 					protocol = RC_TYPE_RC6_MCE;
262 					toggle = !!(scancode & RC6_6A_MCE_TOGGLE_MASK);
263 					scancode &= ~RC6_6A_MCE_TOGGLE_MASK;
264 				} else {
265 					protocol = RC_BIT_RC6_6A_32;
266 					toggle = 0;
267 				}
268 				break;
269 			default:
270 				IR_dprintk(1, "RC6(6A) unsupported length\n");
271 				goto out;
272 			}
273 
274 			IR_dprintk(1, "RC6(6A) proto 0x%04x, scancode 0x%08x (toggle: %u)\n",
275 				   protocol, scancode, toggle);
276 			break;
277 		default:
278 			IR_dprintk(1, "RC6 unknown mode\n");
279 			goto out;
280 		}
281 
282 		rc_keydown(dev, protocol, scancode, toggle);
283 		data->state = STATE_INACTIVE;
284 		return 0;
285 	}
286 
287 out:
288 	IR_dprintk(1, "RC6 decode failed at state %i (%uus %s)\n",
289 		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
290 	data->state = STATE_INACTIVE;
291 	return -EINVAL;
292 }
293 
294 static struct ir_raw_handler rc6_handler = {
295 	.protocols	= RC_BIT_RC6_0 | RC_BIT_RC6_6A_20 |
296 			  RC_BIT_RC6_6A_24 | RC_BIT_RC6_6A_32 |
297 			  RC_BIT_RC6_MCE,
298 	.decode		= ir_rc6_decode,
299 };
300 
301 static int __init ir_rc6_decode_init(void)
302 {
303 	ir_raw_handler_register(&rc6_handler);
304 
305 	printk(KERN_INFO "IR RC6 protocol handler initialized\n");
306 	return 0;
307 }
308 
309 static void __exit ir_rc6_decode_exit(void)
310 {
311 	ir_raw_handler_unregister(&rc6_handler);
312 }
313 
314 module_init(ir_rc6_decode_init);
315 module_exit(ir_rc6_decode_exit);
316 
317 MODULE_LICENSE("GPL");
318 MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
319 MODULE_DESCRIPTION("RC6 IR protocol decoder");
320