1 // SPDX-License-Identifier: GPL-2.0
2 // ir-rc5-decoder.c - decoder for RC5(x) and StreamZap protocols
3 //
4 // Copyright (C) 2010 by Mauro Carvalho Chehab
5 // Copyright (C) 2010 by Jarod Wilson <jarod@redhat.com>
6 
7 /*
8  * This decoder handles the 14 bit RC5 protocol, 15 bit "StreamZap" protocol
9  * and 20 bit RC5x protocol.
10  */
11 
12 #include "rc-core-priv.h"
13 #include <linux/module.h>
14 
15 #define RC5_NBITS		14
16 #define RC5_SZ_NBITS		15
17 #define RC5X_NBITS		20
18 #define CHECK_RC5X_NBITS	8
19 #define RC5_UNIT		889 /* us */
20 #define RC5_BIT_START		(1 * RC5_UNIT)
21 #define RC5_BIT_END		(1 * RC5_UNIT)
22 #define RC5X_SPACE		(4 * RC5_UNIT)
23 #define RC5_TRAILER		(6 * RC5_UNIT) /* In reality, approx 100 */
24 
25 enum rc5_state {
26 	STATE_INACTIVE,
27 	STATE_BIT_START,
28 	STATE_BIT_END,
29 	STATE_CHECK_RC5X,
30 	STATE_FINISHED,
31 };
32 
33 /**
34  * ir_rc5_decode() - Decode one RC-5 pulse or space
35  * @dev:	the struct rc_dev descriptor of the device
36  * @ev:		the struct ir_raw_event descriptor of the pulse/space
37  *
38  * This function returns -EINVAL if the pulse violates the state machine
39  */
40 static int ir_rc5_decode(struct rc_dev *dev, struct ir_raw_event ev)
41 {
42 	struct rc5_dec *data = &dev->raw->rc5;
43 	u8 toggle;
44 	u32 scancode;
45 	enum rc_proto protocol;
46 
47 	if (!is_timing_event(ev)) {
48 		if (ev.overflow)
49 			data->state = STATE_INACTIVE;
50 		return 0;
51 	}
52 
53 	if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
54 		goto out;
55 
56 again:
57 	dev_dbg(&dev->dev, "RC5(x/sz) decode started at state %i (%uus %s)\n",
58 		data->state, ev.duration, TO_STR(ev.pulse));
59 
60 	if (!geq_margin(ev.duration, RC5_UNIT, RC5_UNIT / 2))
61 		return 0;
62 
63 	switch (data->state) {
64 
65 	case STATE_INACTIVE:
66 		if (!ev.pulse)
67 			break;
68 
69 		data->state = STATE_BIT_START;
70 		data->count = 1;
71 		decrease_duration(&ev, RC5_BIT_START);
72 		goto again;
73 
74 	case STATE_BIT_START:
75 		if (!ev.pulse && geq_margin(ev.duration, RC5_TRAILER, RC5_UNIT / 2)) {
76 			data->state = STATE_FINISHED;
77 			goto again;
78 		}
79 
80 		if (!eq_margin(ev.duration, RC5_BIT_START, RC5_UNIT / 2))
81 			break;
82 
83 		data->bits <<= 1;
84 		if (!ev.pulse)
85 			data->bits |= 1;
86 		data->count++;
87 		data->state = STATE_BIT_END;
88 		return 0;
89 
90 	case STATE_BIT_END:
91 		if (data->count == CHECK_RC5X_NBITS)
92 			data->state = STATE_CHECK_RC5X;
93 		else
94 			data->state = STATE_BIT_START;
95 
96 		decrease_duration(&ev, RC5_BIT_END);
97 		goto again;
98 
99 	case STATE_CHECK_RC5X:
100 		if (!ev.pulse && geq_margin(ev.duration, RC5X_SPACE, RC5_UNIT / 2)) {
101 			data->is_rc5x = true;
102 			decrease_duration(&ev, RC5X_SPACE);
103 		} else
104 			data->is_rc5x = false;
105 		data->state = STATE_BIT_START;
106 		goto again;
107 
108 	case STATE_FINISHED:
109 		if (ev.pulse)
110 			break;
111 
112 		if (data->is_rc5x && data->count == RC5X_NBITS) {
113 			/* RC5X */
114 			u8 xdata, command, system;
115 			if (!(dev->enabled_protocols & RC_PROTO_BIT_RC5X_20)) {
116 				data->state = STATE_INACTIVE;
117 				return 0;
118 			}
119 			xdata    = (data->bits & 0x0003F) >> 0;
120 			command  = (data->bits & 0x00FC0) >> 6;
121 			system   = (data->bits & 0x1F000) >> 12;
122 			toggle   = (data->bits & 0x20000) ? 1 : 0;
123 			command += (data->bits & 0x40000) ? 0 : 0x40;
124 			scancode = system << 16 | command << 8 | xdata;
125 			protocol = RC_PROTO_RC5X_20;
126 
127 		} else if (!data->is_rc5x && data->count == RC5_NBITS) {
128 			/* RC5 */
129 			u8 command, system;
130 			if (!(dev->enabled_protocols & RC_PROTO_BIT_RC5)) {
131 				data->state = STATE_INACTIVE;
132 				return 0;
133 			}
134 			command  = (data->bits & 0x0003F) >> 0;
135 			system   = (data->bits & 0x007C0) >> 6;
136 			toggle   = (data->bits & 0x00800) ? 1 : 0;
137 			command += (data->bits & 0x01000) ? 0 : 0x40;
138 			scancode = system << 8 | command;
139 			protocol = RC_PROTO_RC5;
140 
141 		} else if (!data->is_rc5x && data->count == RC5_SZ_NBITS) {
142 			/* RC5 StreamZap */
143 			u8 command, system;
144 			if (!(dev->enabled_protocols & RC_PROTO_BIT_RC5_SZ)) {
145 				data->state = STATE_INACTIVE;
146 				return 0;
147 			}
148 			command  = (data->bits & 0x0003F) >> 0;
149 			system   = (data->bits & 0x02FC0) >> 6;
150 			toggle   = (data->bits & 0x01000) ? 1 : 0;
151 			scancode = system << 6 | command;
152 			protocol = RC_PROTO_RC5_SZ;
153 
154 		} else
155 			break;
156 
157 		dev_dbg(&dev->dev, "RC5(x/sz) scancode 0x%06x (p: %u, t: %u)\n",
158 			scancode, protocol, toggle);
159 
160 		rc_keydown(dev, protocol, scancode, toggle);
161 		data->state = STATE_INACTIVE;
162 		return 0;
163 	}
164 
165 out:
166 	dev_dbg(&dev->dev, "RC5(x/sz) decode failed at state %i count %d (%uus %s)\n",
167 		data->state, data->count, ev.duration, TO_STR(ev.pulse));
168 	data->state = STATE_INACTIVE;
169 	return -EINVAL;
170 }
171 
172 static const struct ir_raw_timings_manchester ir_rc5_timings = {
173 	.leader_pulse		= RC5_UNIT,
174 	.clock			= RC5_UNIT,
175 	.trailer_space		= RC5_UNIT * 10,
176 };
177 
178 static const struct ir_raw_timings_manchester ir_rc5x_timings[2] = {
179 	{
180 		.leader_pulse		= RC5_UNIT,
181 		.clock			= RC5_UNIT,
182 		.trailer_space		= RC5X_SPACE,
183 	},
184 	{
185 		.clock			= RC5_UNIT,
186 		.trailer_space		= RC5_UNIT * 10,
187 	},
188 };
189 
190 static const struct ir_raw_timings_manchester ir_rc5_sz_timings = {
191 	.leader_pulse			= RC5_UNIT,
192 	.clock				= RC5_UNIT,
193 	.trailer_space			= RC5_UNIT * 10,
194 };
195 
196 /**
197  * ir_rc5_encode() - Encode a scancode as a stream of raw events
198  *
199  * @protocol:	protocol variant to encode
200  * @scancode:	scancode to encode
201  * @events:	array of raw ir events to write into
202  * @max:	maximum size of @events
203  *
204  * Returns:	The number of events written.
205  *		-ENOBUFS if there isn't enough space in the array to fit the
206  *		encoding. In this case all @max events will have been written.
207  *		-EINVAL if the scancode is ambiguous or invalid.
208  */
209 static int ir_rc5_encode(enum rc_proto protocol, u32 scancode,
210 			 struct ir_raw_event *events, unsigned int max)
211 {
212 	int ret;
213 	struct ir_raw_event *e = events;
214 	unsigned int data, xdata, command, commandx, system, pre_space_data;
215 
216 	/* Detect protocol and convert scancode to raw data */
217 	if (protocol == RC_PROTO_RC5) {
218 		/* decode scancode */
219 		command  = (scancode & 0x003f) >> 0;
220 		commandx = (scancode & 0x0040) >> 6;
221 		system   = (scancode & 0x1f00) >> 8;
222 		/* encode data */
223 		data = !commandx << 12 | system << 6 | command;
224 
225 		/* First bit is encoded by leader_pulse */
226 		ret = ir_raw_gen_manchester(&e, max, &ir_rc5_timings,
227 					    RC5_NBITS - 1, data);
228 		if (ret < 0)
229 			return ret;
230 	} else if (protocol == RC_PROTO_RC5X_20) {
231 		/* decode scancode */
232 		xdata    = (scancode & 0x00003f) >> 0;
233 		command  = (scancode & 0x003f00) >> 8;
234 		commandx = !(scancode & 0x004000);
235 		system   = (scancode & 0x1f0000) >> 16;
236 
237 		/* encode data */
238 		data = commandx << 18 | system << 12 | command << 6 | xdata;
239 
240 		/* First bit is encoded by leader_pulse */
241 		pre_space_data = data >> (RC5X_NBITS - CHECK_RC5X_NBITS);
242 		ret = ir_raw_gen_manchester(&e, max, &ir_rc5x_timings[0],
243 					    CHECK_RC5X_NBITS - 1,
244 					    pre_space_data);
245 		if (ret < 0)
246 			return ret;
247 		ret = ir_raw_gen_manchester(&e, max - (e - events),
248 					    &ir_rc5x_timings[1],
249 					    RC5X_NBITS - CHECK_RC5X_NBITS,
250 					    data);
251 		if (ret < 0)
252 			return ret;
253 	} else if (protocol == RC_PROTO_RC5_SZ) {
254 		/* RC5-SZ scancode is raw enough for Manchester as it is */
255 		/* First bit is encoded by leader_pulse */
256 		ret = ir_raw_gen_manchester(&e, max, &ir_rc5_sz_timings,
257 					    RC5_SZ_NBITS - 1,
258 					    scancode & 0x2fff);
259 		if (ret < 0)
260 			return ret;
261 	} else {
262 		return -EINVAL;
263 	}
264 
265 	return e - events;
266 }
267 
268 static struct ir_raw_handler rc5_handler = {
269 	.protocols	= RC_PROTO_BIT_RC5 | RC_PROTO_BIT_RC5X_20 |
270 							RC_PROTO_BIT_RC5_SZ,
271 	.decode		= ir_rc5_decode,
272 	.encode		= ir_rc5_encode,
273 	.carrier	= 36000,
274 	.min_timeout	= RC5_TRAILER,
275 };
276 
277 static int __init ir_rc5_decode_init(void)
278 {
279 	ir_raw_handler_register(&rc5_handler);
280 
281 	printk(KERN_INFO "IR RC5(x/sz) protocol handler initialized\n");
282 	return 0;
283 }
284 
285 static void __exit ir_rc5_decode_exit(void)
286 {
287 	ir_raw_handler_unregister(&rc5_handler);
288 }
289 
290 module_init(ir_rc5_decode_init);
291 module_exit(ir_rc5_decode_exit);
292 
293 MODULE_LICENSE("GPL v2");
294 MODULE_AUTHOR("Mauro Carvalho Chehab and Jarod Wilson");
295 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
296 MODULE_DESCRIPTION("RC5(x/sz) IR protocol decoder");
297