1 /* ir-nec-decoder.c - handle NEC IR Pulse/Space protocol
3 * Copyright (C) 2010 by Mauro Carvalho Chehab
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation version 2 of the License.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
15 #include <linux/bitrev.h>
16 #include <linux/module.h>
17 #include "rc-core-priv.h"
20 #define NEC_UNIT 562500 /* ns */
21 #define NEC_HEADER_PULSE (16 * NEC_UNIT)
22 #define NECX_HEADER_PULSE (8 * NEC_UNIT) /* Less common NEC variant */
23 #define NEC_HEADER_SPACE (8 * NEC_UNIT)
24 #define NEC_REPEAT_SPACE (4 * NEC_UNIT)
25 #define NEC_BIT_PULSE (1 * NEC_UNIT)
26 #define NEC_BIT_0_SPACE (1 * NEC_UNIT)
27 #define NEC_BIT_1_SPACE (3 * NEC_UNIT)
28 #define NEC_TRAILER_PULSE (1 * NEC_UNIT)
29 #define NEC_TRAILER_SPACE (10 * NEC_UNIT) /* even longer in reality */
30 #define NECX_REPEAT_BITS 1
42 * ir_nec_decode() - Decode one NEC pulse or space
43 * @dev: the struct rc_dev descriptor of the device
44 * @ev: the struct ir_raw_event descriptor of the pulse/space
46 * This function returns -EINVAL if the pulse violates the state machine
48 static int ir_nec_decode(struct rc_dev *dev, struct ir_raw_event ev)
50 struct nec_dec *data = &dev->raw->nec;
52 enum rc_proto rc_proto;
53 u8 address, not_address, command, not_command;
55 if (!is_timing_event(ev)) {
57 data->state = STATE_INACTIVE;
61 IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n",
62 data->state, TO_US(ev.duration), TO_STR(ev.pulse));
64 switch (data->state) {
70 if (eq_margin(ev.duration, NEC_HEADER_PULSE, NEC_UNIT * 2)) {
71 data->is_nec_x = false;
72 data->necx_repeat = false;
73 } else if (eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2))
74 data->is_nec_x = true;
79 data->state = STATE_HEADER_SPACE;
82 case STATE_HEADER_SPACE:
86 if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT)) {
87 data->state = STATE_BIT_PULSE;
89 } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {
90 data->state = STATE_TRAILER_PULSE;
100 if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
103 data->state = STATE_BIT_SPACE;
106 case STATE_BIT_SPACE:
110 if (data->necx_repeat && data->count == NECX_REPEAT_BITS &&
111 geq_margin(ev.duration,
112 NEC_TRAILER_SPACE, NEC_UNIT / 2)) {
113 IR_dprintk(1, "Repeat last key\n");
115 data->state = STATE_INACTIVE;
118 } else if (data->count > NECX_REPEAT_BITS)
119 data->necx_repeat = false;
122 if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
124 else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
128 if (data->count == NEC_NBITS)
129 data->state = STATE_TRAILER_PULSE;
131 data->state = STATE_BIT_PULSE;
135 case STATE_TRAILER_PULSE:
139 if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
142 data->state = STATE_TRAILER_SPACE;
145 case STATE_TRAILER_SPACE:
149 if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
152 if (data->count == NEC_NBITS) {
153 address = bitrev8((data->bits >> 24) & 0xff);
154 not_address = bitrev8((data->bits >> 16) & 0xff);
155 command = bitrev8((data->bits >> 8) & 0xff);
156 not_command = bitrev8((data->bits >> 0) & 0xff);
158 scancode = ir_nec_bytes_to_scancode(address,
165 data->necx_repeat = true;
167 rc_keydown(dev, rc_proto, scancode, 0);
172 data->state = STATE_INACTIVE;
176 IR_dprintk(1, "NEC decode failed at count %d state %d (%uus %s)\n",
177 data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse));
178 data->state = STATE_INACTIVE;
183 * ir_nec_scancode_to_raw() - encode an NEC scancode ready for modulation.
184 * @protocol: specific protocol to use
185 * @scancode: a single NEC scancode.
187 static u32 ir_nec_scancode_to_raw(enum rc_proto protocol, u32 scancode)
189 unsigned int addr, addr_inv, data, data_inv;
191 data = scancode & 0xff;
193 if (protocol == RC_PROTO_NEC32) {
194 /* 32-bit NEC (used by Apple and TiVo remotes) */
195 /* scan encoding: aaAAddDD */
196 addr_inv = (scancode >> 24) & 0xff;
197 addr = (scancode >> 16) & 0xff;
198 data_inv = (scancode >> 8) & 0xff;
199 } else if (protocol == RC_PROTO_NECX) {
201 /* scan encoding AAaaDD */
202 addr = (scancode >> 16) & 0xff;
203 addr_inv = (scancode >> 8) & 0xff;
204 data_inv = data ^ 0xff;
207 /* scan encoding: AADD */
208 addr = (scancode >> 8) & 0xff;
209 addr_inv = addr ^ 0xff;
210 data_inv = data ^ 0xff;
213 /* raw encoding: ddDDaaAA */
214 return data_inv << 24 |
220 static const struct ir_raw_timings_pd ir_nec_timings = {
221 .header_pulse = NEC_HEADER_PULSE,
222 .header_space = NEC_HEADER_SPACE,
223 .bit_pulse = NEC_BIT_PULSE,
224 .bit_space[0] = NEC_BIT_0_SPACE,
225 .bit_space[1] = NEC_BIT_1_SPACE,
226 .trailer_pulse = NEC_TRAILER_PULSE,
227 .trailer_space = NEC_TRAILER_SPACE,
232 * ir_nec_encode() - Encode a scancode as a stream of raw events
234 * @protocol: protocol to encode
235 * @scancode: scancode to encode
236 * @events: array of raw ir events to write into
237 * @max: maximum size of @events
239 * Returns: The number of events written.
240 * -ENOBUFS if there isn't enough space in the array to fit the
241 * encoding. In this case all @max events will have been written.
243 static int ir_nec_encode(enum rc_proto protocol, u32 scancode,
244 struct ir_raw_event *events, unsigned int max)
246 struct ir_raw_event *e = events;
250 /* Convert a NEC scancode to raw NEC data */
251 raw = ir_nec_scancode_to_raw(protocol, scancode);
253 /* Modulate the raw data using a pulse distance modulation */
254 ret = ir_raw_gen_pd(&e, max, &ir_nec_timings, NEC_NBITS, raw);
261 static struct ir_raw_handler nec_handler = {
262 .protocols = RC_PROTO_BIT_NEC | RC_PROTO_BIT_NECX |
264 .decode = ir_nec_decode,
265 .encode = ir_nec_encode,
268 static int __init ir_nec_decode_init(void)
270 ir_raw_handler_register(&nec_handler);
272 printk(KERN_INFO "IR NEC protocol handler initialized\n");
276 static void __exit ir_nec_decode_exit(void)
278 ir_raw_handler_unregister(&nec_handler);
281 module_init(ir_nec_decode_init);
282 module_exit(ir_nec_decode_exit);
284 MODULE_LICENSE("GPL");
285 MODULE_AUTHOR("Mauro Carvalho Chehab");
286 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
287 MODULE_DESCRIPTION("NEC IR protocol decoder");