1/* ir-sharp-decoder.c - handle Sharp IR Pulse/Space protocol
2 *
3 * Copyright (C) 2013-2014 Imagination Technologies Ltd.
4 *
5 * Based on NEC decoder:
6 * Copyright (C) 2010 by Mauro Carvalho Chehab
7 *
8 * This program is free software; you can redistribute it and/or modify
9 *  it under the terms of the GNU General Public License as published by
10 *  the Free Software Foundation version 2 of the License.
11 *
12 *  This program is distributed in the hope that it will be useful,
13 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
14 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 *  GNU General Public License for more details.
16 */
17
18#include <linux/bitrev.h>
19#include <linux/module.h>
20#include "rc-core-priv.h"
21
22#define SHARP_NBITS		15
23#define SHARP_UNIT		40000  /* ns */
24#define SHARP_BIT_PULSE		(8    * SHARP_UNIT) /* 320us */
25#define SHARP_BIT_0_PERIOD	(25   * SHARP_UNIT) /* 1ms (680us space) */
26#define SHARP_BIT_1_PERIOD	(50   * SHARP_UNIT) /* 2ms (1680ms space) */
27#define SHARP_ECHO_SPACE	(1000 * SHARP_UNIT) /* 40 ms */
28#define SHARP_TRAILER_SPACE	(125  * SHARP_UNIT) /* 5 ms (even longer) */
29
30enum sharp_state {
31	STATE_INACTIVE,
32	STATE_BIT_PULSE,
33	STATE_BIT_SPACE,
34	STATE_TRAILER_PULSE,
35	STATE_ECHO_SPACE,
36	STATE_TRAILER_SPACE,
37};
38
39/**
40 * ir_sharp_decode() - Decode one Sharp pulse or space
41 * @dev:	the struct rc_dev descriptor of the device
42 * @duration:	the struct ir_raw_event descriptor of the pulse/space
43 *
44 * This function returns -EINVAL if the pulse violates the state machine
45 */
46static int ir_sharp_decode(struct rc_dev *dev, struct ir_raw_event ev)
47{
48	struct sharp_dec *data = &dev->raw->sharp;
49	u32 msg, echo, address, command, scancode;
50
51	if (!(dev->enabled_protocols & RC_BIT_SHARP))
52		return 0;
53
54	if (!is_timing_event(ev)) {
55		if (ev.reset)
56			data->state = STATE_INACTIVE;
57		return 0;
58	}
59
60	IR_dprintk(2, "Sharp decode started at state %d (%uus %s)\n",
61		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
62
63	switch (data->state) {
64
65	case STATE_INACTIVE:
66		if (!ev.pulse)
67			break;
68
69		if (!eq_margin(ev.duration, SHARP_BIT_PULSE,
70			       SHARP_BIT_PULSE / 2))
71			break;
72
73		data->count = 0;
74		data->pulse_len = ev.duration;
75		data->state = STATE_BIT_SPACE;
76		return 0;
77
78	case STATE_BIT_PULSE:
79		if (!ev.pulse)
80			break;
81
82		if (!eq_margin(ev.duration, SHARP_BIT_PULSE,
83			       SHARP_BIT_PULSE / 2))
84			break;
85
86		data->pulse_len = ev.duration;
87		data->state = STATE_BIT_SPACE;
88		return 0;
89
90	case STATE_BIT_SPACE:
91		if (ev.pulse)
92			break;
93
94		data->bits <<= 1;
95		if (eq_margin(data->pulse_len + ev.duration, SHARP_BIT_1_PERIOD,
96			      SHARP_BIT_PULSE * 2))
97			data->bits |= 1;
98		else if (!eq_margin(data->pulse_len + ev.duration,
99				    SHARP_BIT_0_PERIOD, SHARP_BIT_PULSE * 2))
100			break;
101		data->count++;
102
103		if (data->count == SHARP_NBITS ||
104		    data->count == SHARP_NBITS * 2)
105			data->state = STATE_TRAILER_PULSE;
106		else
107			data->state = STATE_BIT_PULSE;
108
109		return 0;
110
111	case STATE_TRAILER_PULSE:
112		if (!ev.pulse)
113			break;
114
115		if (!eq_margin(ev.duration, SHARP_BIT_PULSE,
116			       SHARP_BIT_PULSE / 2))
117			break;
118
119		if (data->count == SHARP_NBITS) {
120			/* exp,chk bits should be 1,0 */
121			if ((data->bits & 0x3) != 0x2)
122				break;
123			data->state = STATE_ECHO_SPACE;
124		} else {
125			data->state = STATE_TRAILER_SPACE;
126		}
127		return 0;
128
129	case STATE_ECHO_SPACE:
130		if (ev.pulse)
131			break;
132
133		if (!eq_margin(ev.duration, SHARP_ECHO_SPACE,
134			       SHARP_ECHO_SPACE / 4))
135			break;
136
137		data->state = STATE_BIT_PULSE;
138
139		return 0;
140
141	case STATE_TRAILER_SPACE:
142		if (ev.pulse)
143			break;
144
145		if (!geq_margin(ev.duration, SHARP_TRAILER_SPACE,
146				SHARP_BIT_PULSE / 2))
147			break;
148
149		/* Validate - command, ext, chk should be inverted in 2nd */
150		msg = (data->bits >> 15) & 0x7fff;
151		echo = data->bits & 0x7fff;
152		if ((msg ^ echo) != 0x3ff) {
153			IR_dprintk(1,
154				   "Sharp checksum error: received 0x%04x, 0x%04x\n",
155				   msg, echo);
156			break;
157		}
158
159		address = bitrev8((msg >> 7) & 0xf8);
160		command = bitrev8((msg >> 2) & 0xff);
161
162		scancode = address << 8 | command;
163		IR_dprintk(1, "Sharp scancode 0x%04x\n", scancode);
164
165		rc_keydown(dev, RC_TYPE_SHARP, scancode, 0);
166		data->state = STATE_INACTIVE;
167		return 0;
168	}
169
170	IR_dprintk(1, "Sharp decode failed at count %d state %d (%uus %s)\n",
171		   data->count, data->state, TO_US(ev.duration),
172		   TO_STR(ev.pulse));
173	data->state = STATE_INACTIVE;
174	return -EINVAL;
175}
176
177static struct ir_raw_handler sharp_handler = {
178	.protocols	= RC_BIT_SHARP,
179	.decode		= ir_sharp_decode,
180};
181
182static int __init ir_sharp_decode_init(void)
183{
184	ir_raw_handler_register(&sharp_handler);
185
186	pr_info("IR Sharp protocol handler initialized\n");
187	return 0;
188}
189
190static void __exit ir_sharp_decode_exit(void)
191{
192	ir_raw_handler_unregister(&sharp_handler);
193}
194
195module_init(ir_sharp_decode_init);
196module_exit(ir_sharp_decode_exit);
197
198MODULE_LICENSE("GPL");
199MODULE_AUTHOR("James Hogan <james.hogan@imgtec.com>");
200MODULE_DESCRIPTION("Sharp IR protocol decoder");
201