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
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 */
ir_nec_decode(struct rc_dev * dev,struct ir_raw_event ev)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.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 */
ir_nec_scancode_to_raw(enum rc_proto protocol,u32 scancode)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 */
ir_nec_encode(enum rc_proto protocol,u32 scancode,struct ir_raw_event * events,unsigned int max)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
ir_nec_decode_init(void)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
ir_nec_decode_exit(void)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