1 /* ir-nec-decoder.c - handle NEC IR Pulse/Space protocol
3 * Copyright (C) 2010 by Mauro Carvalho Chehab <mchehab@redhat.com>
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 "ir-core-priv.h"
19 #define NEC_UNIT 562500 /* ns */
20 #define NEC_HEADER_PULSE (16 * NEC_UNIT)
21 #define NECX_HEADER_PULSE (8 * NEC_UNIT) /* Less common NEC variant */
22 #define NEC_HEADER_SPACE (8 * NEC_UNIT)
23 #define NEC_REPEAT_SPACE (8 * NEC_UNIT)
24 #define NEC_BIT_PULSE (1 * NEC_UNIT)
25 #define NEC_BIT_0_SPACE (1 * NEC_UNIT)
26 #define NEC_BIT_1_SPACE (3 * NEC_UNIT)
27 #define NEC_TRAILER_PULSE (1 * NEC_UNIT)
28 #define NEC_TRAILER_SPACE (10 * NEC_UNIT) /* even longer in reality */
40 * ir_nec_decode() - Decode one NEC pulse or space
41 * @input_dev: the struct input_dev descriptor of the device
42 * @duration: the struct ir_raw_event descriptor of the pulse/space
44 * This function returns -EINVAL if the pulse violates the state machine
46 static int ir_nec_decode(struct input_dev *input_dev, struct ir_raw_event ev)
48 struct ir_input_dev *ir_dev = input_get_drvdata(input_dev);
49 struct nec_dec *data = &ir_dev->raw->nec;
51 u8 address, not_address, command, not_command;
53 if (!(ir_dev->raw->enabled_protocols & IR_TYPE_NEC))
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 !eq_margin(ev.duration, NECX_HEADER_PULSE, NEC_UNIT / 2))
75 data->state = STATE_HEADER_SPACE;
78 case STATE_HEADER_SPACE:
82 if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT / 2)) {
83 data->state = STATE_BIT_PULSE;
85 } else if (eq_margin(ev.duration, NEC_REPEAT_SPACE, NEC_UNIT / 2)) {
87 IR_dprintk(1, "Repeat last key\n");
88 data->state = STATE_TRAILER_PULSE;
98 if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
101 data->state = STATE_BIT_SPACE;
104 case STATE_BIT_SPACE:
109 if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
111 else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
115 if (data->count == NEC_NBITS)
116 data->state = STATE_TRAILER_PULSE;
118 data->state = STATE_BIT_PULSE;
122 case STATE_TRAILER_PULSE:
126 if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
129 data->state = STATE_TRAILER_SPACE;
132 case STATE_TRAILER_SPACE:
136 if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
139 address = bitrev8((data->bits >> 24) & 0xff);
140 not_address = bitrev8((data->bits >> 16) & 0xff);
141 command = bitrev8((data->bits >> 8) & 0xff);
142 not_command = bitrev8((data->bits >> 0) & 0xff);
144 if ((command ^ not_command) != 0xff) {
145 IR_dprintk(1, "NEC checksum error: received 0x%08x\n",
150 if ((address ^ not_address) != 0xff) {
152 scancode = address << 16 |
155 IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode);
158 scancode = address << 8 | command;
159 IR_dprintk(1, "NEC scancode 0x%04x\n", scancode);
162 ir_keydown(input_dev, scancode, 0);
163 data->state = STATE_INACTIVE;
167 IR_dprintk(1, "NEC decode failed at state %d (%uus %s)\n",
168 data->state, TO_US(ev.duration), TO_STR(ev.pulse));
169 data->state = STATE_INACTIVE;
173 static struct ir_raw_handler nec_handler = {
174 .protocols = IR_TYPE_NEC,
175 .decode = ir_nec_decode,
178 static int __init ir_nec_decode_init(void)
180 ir_raw_handler_register(&nec_handler);
182 printk(KERN_INFO "IR NEC protocol handler initialized\n");
186 static void __exit ir_nec_decode_exit(void)
188 ir_raw_handler_unregister(&nec_handler);
191 module_init(ir_nec_decode_init);
192 module_exit(ir_nec_decode_exit);
194 MODULE_LICENSE("GPL");
195 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
196 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
197 MODULE_DESCRIPTION("NEC IR protocol decoder");