1 // SPDX-License-Identifier: GPL-2.0
2 // ir-nec-decoder.c - handle NEC IR Pulse/Space protocol
3 //
4 // Copyright (C) 2010 by Mauro Carvalho Chehab
5 
6 #include <linux/bitrev.h>
7 #include <linux/module.h>
8 #include "rc-core-priv.h"
9 
10 #define NEC_NBITS		32
11 #define NEC_UNIT		562500  /* ns */
12 #define NEC_HEADER_PULSE	(16 * NEC_UNIT)
13 #define NECX_HEADER_PULSE	(8  * NEC_UNIT) /* Less common NEC variant */
14 #define NEC_HEADER_SPACE	(8  * NEC_UNIT)
15 #define NEC_REPEAT_SPACE	(4  * NEC_UNIT)
16 #define NEC_BIT_PULSE		(1  * NEC_UNIT)
17 #define NEC_BIT_0_SPACE		(1  * NEC_UNIT)
18 #define NEC_BIT_1_SPACE		(3  * NEC_UNIT)
19 #define	NEC_TRAILER_PULSE	(1  * NEC_UNIT)
20 #define	NEC_TRAILER_SPACE	(10 * NEC_UNIT) /* even longer in reality */
21 #define NECX_REPEAT_BITS	1
22 
23 enum nec_state {
24 	STATE_INACTIVE,
25 	STATE_HEADER_SPACE,
26 	STATE_BIT_PULSE,
27 	STATE_BIT_SPACE,
28 	STATE_TRAILER_PULSE,
29 	STATE_TRAILER_SPACE,
30 };
31 
32 /**
33  * ir_nec_decode() - Decode one NEC pulse or space
34  * @dev:	the struct rc_dev descriptor of the device
35  * @ev:		the struct ir_raw_event descriptor of the pulse/space
36  *
37  * This function returns -EINVAL if the pulse violates the state machine
38  */
39 static int ir_nec_decode(struct rc_dev *dev, struct ir_raw_event ev)
40 {
41 	struct nec_dec *data = &dev->raw->nec;
42 	u32 scancode;
43 	enum rc_proto rc_proto;
44 	u8 address, not_address, command, not_command;
45 
46 	if (!is_timing_event(ev)) {
47 		if (ev.reset)
48 			data->state = STATE_INACTIVE;
49 		return 0;
50 	}
51 
52 	dev_dbg(&dev->dev, "NEC decode started at state %d (%uus %s)\n",
53 		data->state, TO_US(ev.duration), TO_STR(ev.pulse));
54 
55 	switch (data->state) {
56 
57 	case STATE_INACTIVE:
58 		if (!ev.pulse)
59 			break;
60 
61 		if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT * 2)) {
62 			data->is_nec_x = false;
63 			data->necx_repeat = false;
64 		} else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2))
65 			data->is_nec_x = true;
66 		else
67 			break;
68 
69 		data->count = 0;
70 		data->state = STATE_HEADER_SPACE;
71 		return 0;
72 
73 	case STATE_HEADER_SPACE:
74 		if (ev.pulse)
75 			break;
76 
77 		if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT)) {
78 			data->state = STATE_BIT_PULSE;
79 			return 0;
80 		} else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {
81 			data->state = STATE_TRAILER_PULSE;
82 			return 0;
83 		}
84 
85 		break;
86 
87 	case STATE_BIT_PULSE:
88 		if (!ev.pulse)
89 			break;
90 
91 		if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
92 			break;
93 
94 		data->state = STATE_BIT_SPACE;
95 		return 0;
96 
97 	case STATE_BIT_SPACE:
98 		if (ev.pulse)
99 			break;
100 
101 		if (data->necx_repeat && data->count == NECX_REPEAT_BITS &&
102 		    geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2)) {
103 			dev_dbg(&dev->dev, "Repeat last key\n");
104 			rc_repeat(dev);
105 			data->state = STATE_INACTIVE;
106 			return 0;
107 		} else if (data->count > NECX_REPEAT_BITS)
108 			data->necx_repeat = false;
109 
110 		data->bits <<= 1;
111 		if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
112 			data->bits |= 1;
113 		else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
114 			break;
115 		data->count++;
116 
117 		if (data->count == NEC_NBITS)
118 			data->state = STATE_TRAILER_PULSE;
119 		else
120 			data->state = STATE_BIT_PULSE;
121 
122 		return 0;
123 
124 	case STATE_TRAILER_PULSE:
125 		if (!ev.pulse)
126 			break;
127 
128 		if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
129 			break;
130 
131 		data->state = STATE_TRAILER_SPACE;
132 		return 0;
133 
134 	case STATE_TRAILER_SPACE:
135 		if (ev.pulse)
136 			break;
137 
138 		if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
139 			break;
140 
141 		if (data->count == NEC_NBITS) {
142 			address     = bitrev8((data->bits >> 24) & 0xff);
143 			not_address = bitrev8((data->bits >> 16) & 0xff);
144 			command	    = bitrev8((data->bits >>  8) & 0xff);
145 			not_command = bitrev8((data->bits >>  0) & 0xff);
146 
147 			scancode = ir_nec_bytes_to_scancode(address,
148 							    not_address,
149 							    command,
150 							    not_command,
151 							    &rc_proto);
152 
153 			if (data->is_nec_x)
154 				data->necx_repeat = true;
155 
156 			rc_keydown(dev, rc_proto, scancode, 0);
157 		} else {
158 			rc_repeat(dev);
159 		}
160 
161 		data->state = STATE_INACTIVE;
162 		return 0;
163 	}
164 
165 	dev_dbg(&dev->dev, "NEC decode failed at count %d state %d (%uus %s)\n",
166 		data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse));
167 	data->state = STATE_INACTIVE;
168 	return -EINVAL;
169 }
170 
171 /**
172  * ir_nec_scancode_to_raw() - encode an NEC scancode ready for modulation.
173  * @protocol:	specific protocol to use
174  * @scancode:	a single NEC scancode.
175  */
176 static u32 ir_nec_scancode_to_raw(enum rc_proto protocol, u32 scancode)
177 {
178 	unsigned int addr, addr_inv, data, data_inv;
179 
180 	data = scancode & 0xff;
181 
182 	if (protocol == RC_PROTO_NEC32) {
183 		/* 32-bit NEC (used by Apple and TiVo remotes) */
184 		/* scan encoding: aaAAddDD */
185 		addr_inv   = (scancode >> 24) & 0xff;
186 		addr       = (scancode >> 16) & 0xff;
187 		data_inv   = (scancode >>  8) & 0xff;
188 	} else if (protocol == RC_PROTO_NECX) {
189 		/* Extended NEC */
190 		/* scan encoding AAaaDD */
191 		addr       = (scancode >> 16) & 0xff;
192 		addr_inv   = (scancode >>  8) & 0xff;
193 		data_inv   = data ^ 0xff;
194 	} else {
195 		/* Normal NEC */
196 		/* scan encoding: AADD */
197 		addr       = (scancode >>  8) & 0xff;
198 		addr_inv   = addr ^ 0xff;
199 		data_inv   = data ^ 0xff;
200 	}
201 
202 	/* raw encoding: ddDDaaAA */
203 	return data_inv << 24 |
204 	       data     << 16 |
205 	       addr_inv <<  8 |
206 	       addr;
207 }
208 
209 static const struct ir_raw_timings_pd ir_nec_timings = {
210 	.header_pulse	= NEC_HEADER_PULSE,
211 	.header_space	= NEC_HEADER_SPACE,
212 	.bit_pulse	= NEC_BIT_PULSE,
213 	.bit_space[0]	= NEC_BIT_0_SPACE,
214 	.bit_space[1]	= NEC_BIT_1_SPACE,
215 	.trailer_pulse	= NEC_TRAILER_PULSE,
216 	.trailer_space	= NEC_TRAILER_SPACE,
217 	.msb_first	= 0,
218 };
219 
220 /**
221  * ir_nec_encode() - Encode a scancode as a stream of raw events
222  *
223  * @protocol:	protocol to encode
224  * @scancode:	scancode to encode
225  * @events:	array of raw ir events to write into
226  * @max:	maximum size of @events
227  *
228  * Returns:	The number of events written.
229  *		-ENOBUFS if there isn't enough space in the array to fit the
230  *		encoding. In this case all @max events will have been written.
231  */
232 static int ir_nec_encode(enum rc_proto protocol, u32 scancode,
233 			 struct ir_raw_event *events, unsigned int max)
234 {
235 	struct ir_raw_event *e = events;
236 	int ret;
237 	u32 raw;
238 
239 	/* Convert a NEC scancode to raw NEC data */
240 	raw = ir_nec_scancode_to_raw(protocol, scancode);
241 
242 	/* Modulate the raw data using a pulse distance modulation */
243 	ret = ir_raw_gen_pd(&e, max, &ir_nec_timings, NEC_NBITS, raw);
244 	if (ret < 0)
245 		return ret;
246 
247 	return e - events;
248 }
249 
250 static struct ir_raw_handler nec_handler = {
251 	.protocols	= RC_PROTO_BIT_NEC | RC_PROTO_BIT_NECX |
252 							RC_PROTO_BIT_NEC32,
253 	.decode		= ir_nec_decode,
254 	.encode		= ir_nec_encode,
255 	.carrier	= 38000,
256 	.min_timeout	= NEC_TRAILER_SPACE,
257 };
258 
259 static int __init ir_nec_decode_init(void)
260 {
261 	ir_raw_handler_register(&nec_handler);
262 
263 	printk(KERN_INFO "IR NEC protocol handler initialized\n");
264 	return 0;
265 }
266 
267 static void __exit ir_nec_decode_exit(void)
268 {
269 	ir_raw_handler_unregister(&nec_handler);
270 }
271 
272 module_init(ir_nec_decode_init);
273 module_exit(ir_nec_decode_exit);
274 
275 MODULE_LICENSE("GPL v2");
276 MODULE_AUTHOR("Mauro Carvalho Chehab");
277 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
278 MODULE_DESCRIPTION("NEC IR protocol decoder");
279