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		563  /* us */
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
23enum 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 */
39static 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.overflow)
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, 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, 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 */
176static 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
209static 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 */
232static 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
250static 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
259static 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
267static void __exit ir_nec_decode_exit(void)
268{
269	ir_raw_handler_unregister(&nec_handler);
270}
271
272module_init(ir_nec_decode_init);
273module_exit(ir_nec_decode_exit);
274
275MODULE_LICENSE("GPL v2");
276MODULE_AUTHOR("Mauro Carvalho Chehab");
277MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
278MODULE_DESCRIPTION("NEC IR protocol decoder");
279