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 
92 	if (!(dev->enabled_protocols &
93 	      (RC_BIT_RC6_0 | RC_BIT_RC6_6A_20 | RC_BIT_RC6_6A_24 |
94 	       RC_BIT_RC6_6A_32 | RC_BIT_RC6_MCE)))
95 		return 0;
96 
97 	if (!is_timing_event(ev)) {
98 		if (ev.reset)
99 			data->state = STATE_INACTIVE;
100 		return 0;
101 	}
102 
103 	if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
104 		goto out;
105 
106 again:
107 	IR_dprintk(2, "RC6 decode started at state %i (%uus %s)\n",
108 		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
109 
110 	if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
111 		return 0;
112 
113 	switch (data->state) {
114 
115 	case STATE_INACTIVE:
116 		if (!ev.pulse)
117 			break;
118 
119 		/* Note: larger margin on first pulse since each RC6_UNIT
120 		   is quite short and some hardware takes some time to
121 		   adjust to the signal */
122 		if (!eq_margin(ev.duration, RC6_PREFIX_PULSE, RC6_UNIT))
123 			break;
124 
125 		data->state = STATE_PREFIX_SPACE;
126 		data->count = 0;
127 		return 0;
128 
129 	case STATE_PREFIX_SPACE:
130 		if (ev.pulse)
131 			break;
132 
133 		if (!eq_margin(ev.duration, RC6_PREFIX_SPACE, RC6_UNIT / 2))
134 			break;
135 
136 		data->state = STATE_HEADER_BIT_START;
137 		data->header = 0;
138 		return 0;
139 
140 	case STATE_HEADER_BIT_START:
141 		if (!eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2))
142 			break;
143 
144 		data->header <<= 1;
145 		if (ev.pulse)
146 			data->header |= 1;
147 		data->count++;
148 		data->state = STATE_HEADER_BIT_END;
149 		return 0;
150 
151 	case STATE_HEADER_BIT_END:
152 		if (!is_transition(&ev, &dev->raw->prev_ev))
153 			break;
154 
155 		if (data->count == RC6_HEADER_NBITS)
156 			data->state = STATE_TOGGLE_START;
157 		else
158 			data->state = STATE_HEADER_BIT_START;
159 
160 		decrease_duration(&ev, RC6_BIT_END);
161 		goto again;
162 
163 	case STATE_TOGGLE_START:
164 		if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
165 			break;
166 
167 		data->toggle = ev.pulse;
168 		data->state = STATE_TOGGLE_END;
169 		return 0;
170 
171 	case STATE_TOGGLE_END:
172 		if (!is_transition(&ev, &dev->raw->prev_ev) ||
173 		    !geq_margin(ev.duration, RC6_TOGGLE_END, RC6_UNIT / 2))
174 			break;
175 
176 		if (!(data->header & RC6_STARTBIT_MASK)) {
177 			IR_dprintk(1, "RC6 invalid start bit\n");
178 			break;
179 		}
180 
181 		data->state = STATE_BODY_BIT_START;
182 		decrease_duration(&ev, RC6_TOGGLE_END);
183 		data->count = 0;
184 		data->body = 0;
185 
186 		switch (rc6_mode(data)) {
187 		case RC6_MODE_0:
188 			data->wanted_bits = RC6_0_NBITS;
189 			break;
190 		case RC6_MODE_6A:
191 			data->wanted_bits = RC6_6A_NBITS;
192 			break;
193 		default:
194 			IR_dprintk(1, "RC6 unknown mode\n");
195 			goto out;
196 		}
197 		goto again;
198 
199 	case STATE_BODY_BIT_START:
200 		if (eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2)) {
201 			/* Discard LSB's that won't fit in data->body */
202 			if (data->count++ < CHAR_BIT * sizeof data->body) {
203 				data->body <<= 1;
204 				if (ev.pulse)
205 					data->body |= 1;
206 			}
207 			data->state = STATE_BODY_BIT_END;
208 			return 0;
209 		} else if (RC6_MODE_6A == rc6_mode(data) && !ev.pulse &&
210 				geq_margin(ev.duration, RC6_SUFFIX_SPACE, RC6_UNIT / 2)) {
211 			data->state = STATE_FINISHED;
212 			goto again;
213 		}
214 		break;
215 
216 	case STATE_BODY_BIT_END:
217 		if (!is_transition(&ev, &dev->raw->prev_ev))
218 			break;
219 
220 		if (data->count == data->wanted_bits)
221 			data->state = STATE_FINISHED;
222 		else
223 			data->state = STATE_BODY_BIT_START;
224 
225 		decrease_duration(&ev, RC6_BIT_END);
226 		goto again;
227 
228 	case STATE_FINISHED:
229 		if (ev.pulse)
230 			break;
231 
232 		switch (rc6_mode(data)) {
233 		case RC6_MODE_0:
234 			scancode = data->body;
235 			toggle = data->toggle;
236 			IR_dprintk(1, "RC6(0) scancode 0x%04x (toggle: %u)\n",
237 				   scancode, toggle);
238 			break;
239 		case RC6_MODE_6A:
240 			if (data->count > CHAR_BIT * sizeof data->body) {
241 				IR_dprintk(1, "RC6 too many (%u) data bits\n",
242 					data->count);
243 				goto out;
244 			}
245 
246 			scancode = data->body;
247 			if (data->count == RC6_6A_32_NBITS &&
248 					(scancode & RC6_6A_LCC_MASK) == RC6_6A_MCE_CC) {
249 				/* MCE RC */
250 				toggle = (scancode & RC6_6A_MCE_TOGGLE_MASK) ? 1 : 0;
251 				scancode &= ~RC6_6A_MCE_TOGGLE_MASK;
252 			} else {
253 				toggle = 0;
254 			}
255 			IR_dprintk(1, "RC6(6A) scancode 0x%08x (toggle: %u)\n",
256 				   scancode, toggle);
257 			break;
258 		default:
259 			IR_dprintk(1, "RC6 unknown mode\n");
260 			goto out;
261 		}
262 
263 		rc_keydown(dev, scancode, toggle);
264 		data->state = STATE_INACTIVE;
265 		return 0;
266 	}
267 
268 out:
269 	IR_dprintk(1, "RC6 decode failed at state %i (%uus %s)\n",
270 		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
271 	data->state = STATE_INACTIVE;
272 	return -EINVAL;
273 }
274 
275 static struct ir_raw_handler rc6_handler = {
276 	.protocols	= RC_BIT_RC6_0 | RC_BIT_RC6_6A_20 |
277 			  RC_BIT_RC6_6A_24 | RC_BIT_RC6_6A_32 |
278 			  RC_BIT_RC6_MCE,
279 	.decode		= ir_rc6_decode,
280 };
281 
282 static int __init ir_rc6_decode_init(void)
283 {
284 	ir_raw_handler_register(&rc6_handler);
285 
286 	printk(KERN_INFO "IR RC6 protocol handler initialized\n");
287 	return 0;
288 }
289 
290 static void __exit ir_rc6_decode_exit(void)
291 {
292 	ir_raw_handler_unregister(&rc6_handler);
293 }
294 
295 module_init(ir_rc6_decode_init);
296 module_exit(ir_rc6_decode_exit);
297 
298 MODULE_LICENSE("GPL");
299 MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
300 MODULE_DESCRIPTION("RC6 IR protocol decoder");
301