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 <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 * @duration: 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 u8 address
, not_address
, command
, not_command
;
53 bool send_32bits
= false;
55 if (!(dev
->raw
->enabled_protocols
& RC_TYPE_NEC
))
58 if (!is_timing_event(ev
)) {
60 data
->state
= STATE_INACTIVE
;
64 IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n",
65 data
->state
, TO_US(ev
.duration
), TO_STR(ev
.pulse
));
67 switch (data
->state
) {
73 if (eq_margin(ev
.duration
, NEC_HEADER_PULSE
, NEC_UNIT
/ 2)) {
74 data
->is_nec_x
= false;
75 data
->necx_repeat
= false;
76 } else if (eq_margin(ev
.duration
, NECX_HEADER_PULSE
, NEC_UNIT
/ 2))
77 data
->is_nec_x
= true;
82 data
->state
= STATE_HEADER_SPACE
;
85 case STATE_HEADER_SPACE
:
89 if (eq_margin(ev
.duration
, NEC_HEADER_SPACE
, NEC_UNIT
/ 2)) {
90 data
->state
= STATE_BIT_PULSE
;
92 } else if (eq_margin(ev
.duration
, NEC_REPEAT_SPACE
, NEC_UNIT
/ 2)) {
93 if (!dev
->keypressed
) {
94 IR_dprintk(1, "Discarding last key repeat: event after key up\n");
97 IR_dprintk(1, "Repeat last key\n");
98 data
->state
= STATE_TRAILER_PULSE
;
105 case STATE_BIT_PULSE
:
109 if (!eq_margin(ev
.duration
, NEC_BIT_PULSE
, NEC_UNIT
/ 2))
112 data
->state
= STATE_BIT_SPACE
;
115 case STATE_BIT_SPACE
:
119 if (data
->necx_repeat
&& data
->count
== NECX_REPEAT_BITS
&&
120 geq_margin(ev
.duration
,
121 NEC_TRAILER_SPACE
, NEC_UNIT
/ 2)) {
122 IR_dprintk(1, "Repeat last key\n");
124 data
->state
= STATE_INACTIVE
;
127 } else if (data
->count
> NECX_REPEAT_BITS
)
128 data
->necx_repeat
= false;
131 if (eq_margin(ev
.duration
, NEC_BIT_1_SPACE
, NEC_UNIT
/ 2))
133 else if (!eq_margin(ev
.duration
, NEC_BIT_0_SPACE
, NEC_UNIT
/ 2))
137 if (data
->count
== NEC_NBITS
)
138 data
->state
= STATE_TRAILER_PULSE
;
140 data
->state
= STATE_BIT_PULSE
;
144 case STATE_TRAILER_PULSE
:
148 if (!eq_margin(ev
.duration
, NEC_TRAILER_PULSE
, NEC_UNIT
/ 2))
151 data
->state
= STATE_TRAILER_SPACE
;
154 case STATE_TRAILER_SPACE
:
158 if (!geq_margin(ev
.duration
, NEC_TRAILER_SPACE
, NEC_UNIT
/ 2))
161 address
= bitrev8((data
->bits
>> 24) & 0xff);
162 not_address
= bitrev8((data
->bits
>> 16) & 0xff);
163 command
= bitrev8((data
->bits
>> 8) & 0xff);
164 not_command
= bitrev8((data
->bits
>> 0) & 0xff);
166 if ((command
^ not_command
) != 0xff) {
167 IR_dprintk(1, "NEC checksum error: received 0x%08x\n",
173 /* NEC transport, but modified protocol, used by at
174 * least Apple and TiVo remotes */
175 scancode
= data
->bits
;
176 IR_dprintk(1, "NEC (modified) scancode 0x%08x\n", scancode
);
177 } else if ((address
^ not_address
) != 0xff) {
179 scancode
= address
<< 16 |
182 IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode
);
185 scancode
= address
<< 8 | command
;
186 IR_dprintk(1, "NEC scancode 0x%04x\n", scancode
);
190 data
->necx_repeat
= true;
192 rc_keydown(dev
, scancode
, 0);
193 data
->state
= STATE_INACTIVE
;
197 IR_dprintk(1, "NEC decode failed at state %d (%uus %s)\n",
198 data
->state
, TO_US(ev
.duration
), TO_STR(ev
.pulse
));
199 data
->state
= STATE_INACTIVE
;
203 static struct ir_raw_handler nec_handler
= {
204 .protocols
= RC_TYPE_NEC
,
205 .decode
= ir_nec_decode
,
208 static int __init
ir_nec_decode_init(void)
210 ir_raw_handler_register(&nec_handler
);
212 printk(KERN_INFO
"IR NEC protocol handler initialized\n");
216 static void __exit
ir_nec_decode_exit(void)
218 ir_raw_handler_unregister(&nec_handler
);
221 module_init(ir_nec_decode_init
);
222 module_exit(ir_nec_decode_exit
);
224 MODULE_LICENSE("GPL");
225 MODULE_AUTHOR("Mauro Carvalho Chehab <mchehab@redhat.com>");
226 MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
227 MODULE_DESCRIPTION("NEC IR protocol decoder");