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		888888 /* ns */
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.reset)
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, TO_US(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 (!is_transition(&ev, &dev->raw->prev_ev))
92 			break;
93 
94 		if (data->count == CHECK_RC5X_NBITS)
95 			data->state = STATE_CHECK_RC5X;
96 		else
97 			data->state = STATE_BIT_START;
98 
99 		decrease_duration(&ev, RC5_BIT_END);
100 		goto again;
101 
102 	case STATE_CHECK_RC5X:
103 		if (!ev.pulse && geq_margin(ev.duration, RC5X_SPACE, RC5_UNIT / 2)) {
104 			data->is_rc5x = true;
105 			decrease_duration(&ev, RC5X_SPACE);
106 		} else
107 			data->is_rc5x = false;
108 		data->state = STATE_BIT_START;
109 		goto again;
110 
111 	case STATE_FINISHED:
112 		if (ev.pulse)
113 			break;
114 
115 		if (data->is_rc5x && data->count == RC5X_NBITS) {
116 			/* RC5X */
117 			u8 xdata, command, system;
118 			if (!(dev->enabled_protocols & RC_PROTO_BIT_RC5X_20)) {
119 				data->state = STATE_INACTIVE;
120 				return 0;
121 			}
122 			xdata    = (data->bits & 0x0003F) >> 0;
123 			command  = (data->bits & 0x00FC0) >> 6;
124 			system   = (data->bits & 0x1F000) >> 12;
125 			toggle   = (data->bits & 0x20000) ? 1 : 0;
126 			command += (data->bits & 0x40000) ? 0 : 0x40;
127 			scancode = system << 16 | command << 8 | xdata;
128 			protocol = RC_PROTO_RC5X_20;
129 
130 		} else if (!data->is_rc5x && data->count == RC5_NBITS) {
131 			/* RC5 */
132 			u8 command, system;
133 			if (!(dev->enabled_protocols & RC_PROTO_BIT_RC5)) {
134 				data->state = STATE_INACTIVE;
135 				return 0;
136 			}
137 			command  = (data->bits & 0x0003F) >> 0;
138 			system   = (data->bits & 0x007C0) >> 6;
139 			toggle   = (data->bits & 0x00800) ? 1 : 0;
140 			command += (data->bits & 0x01000) ? 0 : 0x40;
141 			scancode = system << 8 | command;
142 			protocol = RC_PROTO_RC5;
143 
144 		} else if (!data->is_rc5x && data->count == RC5_SZ_NBITS) {
145 			/* RC5 StreamZap */
146 			u8 command, system;
147 			if (!(dev->enabled_protocols & RC_PROTO_BIT_RC5_SZ)) {
148 				data->state = STATE_INACTIVE;
149 				return 0;
150 			}
151 			command  = (data->bits & 0x0003F) >> 0;
152 			system   = (data->bits & 0x02FC0) >> 6;
153 			toggle   = (data->bits & 0x01000) ? 1 : 0;
154 			scancode = system << 6 | command;
155 			protocol = RC_PROTO_RC5_SZ;
156 
157 		} else
158 			break;
159 
160 		dev_dbg(&dev->dev, "RC5(x/sz) scancode 0x%06x (p: %u, t: %u)\n",
161 			scancode, protocol, toggle);
162 
163 		rc_keydown(dev, protocol, scancode, toggle);
164 		data->state = STATE_INACTIVE;
165 		return 0;
166 	}
167 
168 out:
169 	dev_dbg(&dev->dev, "RC5(x/sz) decode failed at state %i count %d (%uus %s)\n",
170 		data->state, data->count, TO_US(ev.duration), TO_STR(ev.pulse));
171 	data->state = STATE_INACTIVE;
172 	return -EINVAL;
173 }
174 
175 static const struct ir_raw_timings_manchester ir_rc5_timings = {
176 	.leader_pulse		= RC5_UNIT,
177 	.clock			= RC5_UNIT,
178 	.trailer_space		= RC5_UNIT * 10,
179 };
180 
181 static const struct ir_raw_timings_manchester ir_rc5x_timings[2] = {
182 	{
183 		.leader_pulse		= RC5_UNIT,
184 		.clock			= RC5_UNIT,
185 		.trailer_space		= RC5X_SPACE,
186 	},
187 	{
188 		.clock			= RC5_UNIT,
189 		.trailer_space		= RC5_UNIT * 10,
190 	},
191 };
192 
193 static const struct ir_raw_timings_manchester ir_rc5_sz_timings = {
194 	.leader_pulse			= RC5_UNIT,
195 	.clock				= RC5_UNIT,
196 	.trailer_space			= RC5_UNIT * 10,
197 };
198 
199 /**
200  * ir_rc5_encode() - Encode a scancode as a stream of raw events
201  *
202  * @protocol:	protocol variant to encode
203  * @scancode:	scancode to encode
204  * @events:	array of raw ir events to write into
205  * @max:	maximum size of @events
206  *
207  * Returns:	The number of events written.
208  *		-ENOBUFS if there isn't enough space in the array to fit the
209  *		encoding. In this case all @max events will have been written.
210  *		-EINVAL if the scancode is ambiguous or invalid.
211  */
212 static int ir_rc5_encode(enum rc_proto protocol, u32 scancode,
213 			 struct ir_raw_event *events, unsigned int max)
214 {
215 	int ret;
216 	struct ir_raw_event *e = events;
217 	unsigned int data, xdata, command, commandx, system, pre_space_data;
218 
219 	/* Detect protocol and convert scancode to raw data */
220 	if (protocol == RC_PROTO_RC5) {
221 		/* decode scancode */
222 		command  = (scancode & 0x003f) >> 0;
223 		commandx = (scancode & 0x0040) >> 6;
224 		system   = (scancode & 0x1f00) >> 8;
225 		/* encode data */
226 		data = !commandx << 12 | system << 6 | command;
227 
228 		/* First bit is encoded by leader_pulse */
229 		ret = ir_raw_gen_manchester(&e, max, &ir_rc5_timings,
230 					    RC5_NBITS - 1, data);
231 		if (ret < 0)
232 			return ret;
233 	} else if (protocol == RC_PROTO_RC5X_20) {
234 		/* decode scancode */
235 		xdata    = (scancode & 0x00003f) >> 0;
236 		command  = (scancode & 0x003f00) >> 8;
237 		commandx = !(scancode & 0x004000);
238 		system   = (scancode & 0x1f0000) >> 16;
239 
240 		/* encode data */
241 		data = commandx << 18 | system << 12 | command << 6 | xdata;
242 
243 		/* First bit is encoded by leader_pulse */
244 		pre_space_data = data >> (RC5X_NBITS - CHECK_RC5X_NBITS);
245 		ret = ir_raw_gen_manchester(&e, max, &ir_rc5x_timings[0],
246 					    CHECK_RC5X_NBITS - 1,
247 					    pre_space_data);
248 		if (ret < 0)
249 			return ret;
250 		ret = ir_raw_gen_manchester(&e, max - (e - events),
251 					    &ir_rc5x_timings[1],
252 					    RC5X_NBITS - CHECK_RC5X_NBITS,
253 					    data);
254 		if (ret < 0)
255 			return ret;
256 	} else if (protocol == RC_PROTO_RC5_SZ) {
257 		/* RC5-SZ scancode is raw enough for Manchester as it is */
258 		/* First bit is encoded by leader_pulse */
259 		ret = ir_raw_gen_manchester(&e, max, &ir_rc5_sz_timings,
260 					    RC5_SZ_NBITS - 1,
261 					    scancode & 0x2fff);
262 		if (ret < 0)
263 			return ret;
264 	} else {
265 		return -EINVAL;
266 	}
267 
268 	return e - events;
269 }
270 
271 static struct ir_raw_handler rc5_handler = {
272 	.protocols	= RC_PROTO_BIT_RC5 | RC_PROTO_BIT_RC5X_20 |
273 							RC_PROTO_BIT_RC5_SZ,
274 	.decode		= ir_rc5_decode,
275 	.encode		= ir_rc5_encode,
276 	.carrier	= 36000,
277 };
278 
279 static int __init ir_rc5_decode_init(void)
280 {
281 	ir_raw_handler_register(&rc5_handler);
282 
283 	printk(KERN_INFO "IR RC5(x/sz) protocol handler initialized\n");
284 	return 0;
285 }
286 
287 static void __exit ir_rc5_decode_exit(void)
288 {
289 	ir_raw_handler_unregister(&rc5_handler);
290 }
291 
292 module_init(ir_rc5_decode_init);
293 module_exit(ir_rc5_decode_exit);
294 
295 MODULE_LICENSE("GPL v2");
296 MODULE_AUTHOR("Mauro Carvalho Chehab and Jarod Wilson");
297 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
298 MODULE_DESCRIPTION("RC5(x/sz) IR protocol decoder");
299