1/* ir-nec-decoder.c - handle NEC IR Pulse/Space protocol
2 *
3 * Copyright (C) 2010 by Mauro Carvalho Chehab
4 *
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.
8 *
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.
13 */
14
15#include <linux/bitrev.h>
16#include <linux/module.h>
17#include "rc-core-priv.h"
18
19#define NEC_NBITS		32
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
31
32enum nec_state {
33	STATE_INACTIVE,
34	STATE_HEADER_SPACE,
35	STATE_BIT_PULSE,
36	STATE_BIT_SPACE,
37	STATE_TRAILER_PULSE,
38	STATE_TRAILER_SPACE,
39};
40
41/**
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
45 *
46 * This function returns -EINVAL if the pulse violates the state machine
47 */
48static int ir_nec_decode(struct rc_dev *dev, struct ir_raw_event ev)
49{
50	struct nec_dec *data = &dev->raw->nec;
51	u32 scancode;
52	u8 address, not_address, command, not_command;
53	bool send_32bits = false;
54
55	if (!(dev->enabled_protocols & RC_BIT_NEC))
56		return 0;
57
58	if (!is_timing_event(ev)) {
59		if (ev.reset)
60			data->state = STATE_INACTIVE;
61		return 0;
62	}
63
64	IR_dprintk(2, "NEC decode started at state %d (%uus %s)\n",
65		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
66
67	switch (data->state) {
68
69	case STATE_INACTIVE:
70		if (!ev.pulse)
71			break;
72
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;
78		else
79			break;
80
81		data->count = 0;
82		data->state = STATE_HEADER_SPACE;
83		return 0;
84
85	case STATE_HEADER_SPACE:
86		if (ev.pulse)
87			break;
88
89		if (eq_margin(ev.duration, NEC_HEADER_SPACE, NEC_UNIT)) {
90			data->state = STATE_BIT_PULSE;
91			return 0;
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");
95			} else {
96				rc_repeat(dev);
97				IR_dprintk(1, "Repeat last key\n");
98				data->state = STATE_TRAILER_PULSE;
99			}
100			return 0;
101		}
102
103		break;
104
105	case STATE_BIT_PULSE:
106		if (!ev.pulse)
107			break;
108
109		if (!eq_margin(ev.duration, NEC_BIT_PULSE, NEC_UNIT / 2))
110			break;
111
112		data->state = STATE_BIT_SPACE;
113		return 0;
114
115	case STATE_BIT_SPACE:
116		if (ev.pulse)
117			break;
118
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");
123				rc_repeat(dev);
124				data->state = STATE_INACTIVE;
125				return 0;
126
127		} else if (data->count > NECX_REPEAT_BITS)
128			data->necx_repeat = false;
129
130		data->bits <<= 1;
131		if (eq_margin(ev.duration, NEC_BIT_1_SPACE, NEC_UNIT / 2))
132			data->bits |= 1;
133		else if (!eq_margin(ev.duration, NEC_BIT_0_SPACE, NEC_UNIT / 2))
134			break;
135		data->count++;
136
137		if (data->count == NEC_NBITS)
138			data->state = STATE_TRAILER_PULSE;
139		else
140			data->state = STATE_BIT_PULSE;
141
142		return 0;
143
144	case STATE_TRAILER_PULSE:
145		if (!ev.pulse)
146			break;
147
148		if (!eq_margin(ev.duration, NEC_TRAILER_PULSE, NEC_UNIT / 2))
149			break;
150
151		data->state = STATE_TRAILER_SPACE;
152		return 0;
153
154	case STATE_TRAILER_SPACE:
155		if (ev.pulse)
156			break;
157
158		if (!geq_margin(ev.duration, NEC_TRAILER_SPACE, NEC_UNIT / 2))
159			break;
160
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);
165
166		if ((command ^ not_command) != 0xff) {
167			IR_dprintk(1, "NEC checksum error: received 0x%08x\n",
168				   data->bits);
169			send_32bits = true;
170		}
171
172		if (send_32bits) {
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) {
178			/* Extended NEC */
179			scancode = address     << 16 |
180				   not_address <<  8 |
181				   command;
182			IR_dprintk(1, "NEC (Ext) scancode 0x%06x\n", scancode);
183		} else {
184			/* Normal NEC */
185			scancode = address << 8 | command;
186			IR_dprintk(1, "NEC scancode 0x%04x\n", scancode);
187		}
188
189		if (data->is_nec_x)
190			data->necx_repeat = true;
191
192		rc_keydown(dev, RC_TYPE_NEC, scancode, 0);
193		data->state = STATE_INACTIVE;
194		return 0;
195	}
196
197	IR_dprintk(1, "NEC decode failed at count %d state %d (%uus %s)\n",
198		   data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse));
199	data->state = STATE_INACTIVE;
200	return -EINVAL;
201}
202
203static struct ir_raw_handler nec_handler = {
204	.protocols	= RC_BIT_NEC,
205	.decode		= ir_nec_decode,
206};
207
208static int __init ir_nec_decode_init(void)
209{
210	ir_raw_handler_register(&nec_handler);
211
212	printk(KERN_INFO "IR NEC protocol handler initialized\n");
213	return 0;
214}
215
216static void __exit ir_nec_decode_exit(void)
217{
218	ir_raw_handler_unregister(&nec_handler);
219}
220
221module_init(ir_nec_decode_init);
222module_exit(ir_nec_decode_exit);
223
224MODULE_LICENSE("GPL");
225MODULE_AUTHOR("Mauro Carvalho Chehab");
226MODULE_AUTHOR("Red Hat Inc. (http://www.redhat.com)");
227MODULE_DESCRIPTION("NEC IR protocol decoder");
228