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 
30 enum 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  */
46 static 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 (!is_timing_event(ev)) {
52 		if (ev.reset)
53 			data->state = STATE_INACTIVE;
54 		return 0;
55 	}
56 
57 	IR_dprintk(2, "Sharp decode started at state %d (%uus %s)\n",
58 		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
59 
60 	switch (data->state) {
61 
62 	case STATE_INACTIVE:
63 		if (!ev.pulse)
64 			break;
65 
66 		if (!eq_margin(ev.duration, SHARP_BIT_PULSE,
67 			       SHARP_BIT_PULSE / 2))
68 			break;
69 
70 		data->count = 0;
71 		data->pulse_len = ev.duration;
72 		data->state = STATE_BIT_SPACE;
73 		return 0;
74 
75 	case STATE_BIT_PULSE:
76 		if (!ev.pulse)
77 			break;
78 
79 		if (!eq_margin(ev.duration, SHARP_BIT_PULSE,
80 			       SHARP_BIT_PULSE / 2))
81 			break;
82 
83 		data->pulse_len = ev.duration;
84 		data->state = STATE_BIT_SPACE;
85 		return 0;
86 
87 	case STATE_BIT_SPACE:
88 		if (ev.pulse)
89 			break;
90 
91 		data->bits <<= 1;
92 		if (eq_margin(data->pulse_len + ev.duration, SHARP_BIT_1_PERIOD,
93 			      SHARP_BIT_PULSE * 2))
94 			data->bits |= 1;
95 		else if (!eq_margin(data->pulse_len + ev.duration,
96 				    SHARP_BIT_0_PERIOD, SHARP_BIT_PULSE * 2))
97 			break;
98 		data->count++;
99 
100 		if (data->count == SHARP_NBITS ||
101 		    data->count == SHARP_NBITS * 2)
102 			data->state = STATE_TRAILER_PULSE;
103 		else
104 			data->state = STATE_BIT_PULSE;
105 
106 		return 0;
107 
108 	case STATE_TRAILER_PULSE:
109 		if (!ev.pulse)
110 			break;
111 
112 		if (!eq_margin(ev.duration, SHARP_BIT_PULSE,
113 			       SHARP_BIT_PULSE / 2))
114 			break;
115 
116 		if (data->count == SHARP_NBITS) {
117 			/* exp,chk bits should be 1,0 */
118 			if ((data->bits & 0x3) != 0x2 &&
119 			/* DENON variant, both chk bits 0 */
120 			    (data->bits & 0x3) != 0x0)
121 				break;
122 			data->state = STATE_ECHO_SPACE;
123 		} else {
124 			data->state = STATE_TRAILER_SPACE;
125 		}
126 		return 0;
127 
128 	case STATE_ECHO_SPACE:
129 		if (ev.pulse)
130 			break;
131 
132 		if (!eq_margin(ev.duration, SHARP_ECHO_SPACE,
133 			       SHARP_ECHO_SPACE / 4))
134 			break;
135 
136 		data->state = STATE_BIT_PULSE;
137 
138 		return 0;
139 
140 	case STATE_TRAILER_SPACE:
141 		if (ev.pulse)
142 			break;
143 
144 		if (!geq_margin(ev.duration, SHARP_TRAILER_SPACE,
145 				SHARP_BIT_PULSE / 2))
146 			break;
147 
148 		/* Validate - command, ext, chk should be inverted in 2nd */
149 		msg = (data->bits >> 15) & 0x7fff;
150 		echo = data->bits & 0x7fff;
151 		if ((msg ^ echo) != 0x3ff) {
152 			IR_dprintk(1,
153 				   "Sharp checksum error: received 0x%04x, 0x%04x\n",
154 				   msg, echo);
155 			break;
156 		}
157 
158 		address = bitrev8((msg >> 7) & 0xf8);
159 		command = bitrev8((msg >> 2) & 0xff);
160 
161 		scancode = address << 8 | command;
162 		IR_dprintk(1, "Sharp scancode 0x%04x\n", scancode);
163 
164 		rc_keydown(dev, RC_PROTO_SHARP, scancode, 0);
165 		data->state = STATE_INACTIVE;
166 		return 0;
167 	}
168 
169 	IR_dprintk(1, "Sharp decode failed at count %d state %d (%uus %s)\n",
170 		   data->count, data->state, TO_US(ev.duration),
171 		   TO_STR(ev.pulse));
172 	data->state = STATE_INACTIVE;
173 	return -EINVAL;
174 }
175 
176 static const struct ir_raw_timings_pd ir_sharp_timings = {
177 	.header_pulse  = 0,
178 	.header_space  = 0,
179 	.bit_pulse     = SHARP_BIT_PULSE,
180 	.bit_space[0]  = SHARP_BIT_0_PERIOD,
181 	.bit_space[1]  = SHARP_BIT_1_PERIOD,
182 	.trailer_pulse = SHARP_BIT_PULSE,
183 	.trailer_space = SHARP_ECHO_SPACE,
184 	.msb_first     = 1,
185 };
186 
187 /**
188  * ir_sharp_encode() - Encode a scancode as a stream of raw events
189  *
190  * @protocol:	protocol to encode
191  * @scancode:	scancode to encode
192  * @events:	array of raw ir events to write into
193  * @max:	maximum size of @events
194  *
195  * Returns:	The number of events written.
196  *		-ENOBUFS if there isn't enough space in the array to fit the
197  *		encoding. In this case all @max events will have been written.
198  */
199 static int ir_sharp_encode(enum rc_proto protocol, u32 scancode,
200 			   struct ir_raw_event *events, unsigned int max)
201 {
202 	struct ir_raw_event *e = events;
203 	int ret;
204 	u32 raw;
205 
206 	raw = (((bitrev8(scancode >> 8) >> 3) << 8) & 0x1f00) |
207 		bitrev8(scancode);
208 	ret = ir_raw_gen_pd(&e, max, &ir_sharp_timings, SHARP_NBITS,
209 			    (raw << 2) | 2);
210 	if (ret < 0)
211 		return ret;
212 
213 	max -= ret;
214 
215 	raw = (((bitrev8(scancode >> 8) >> 3) << 8) & 0x1f00) |
216 		bitrev8(~scancode);
217 	ret = ir_raw_gen_pd(&e, max, &ir_sharp_timings, SHARP_NBITS,
218 			    (raw << 2) | 1);
219 	if (ret < 0)
220 		return ret;
221 
222 	return e - events;
223 }
224 
225 static struct ir_raw_handler sharp_handler = {
226 	.protocols	= RC_PROTO_BIT_SHARP,
227 	.decode		= ir_sharp_decode,
228 	.encode		= ir_sharp_encode,
229 };
230 
231 static int __init ir_sharp_decode_init(void)
232 {
233 	ir_raw_handler_register(&sharp_handler);
234 
235 	pr_info("IR Sharp protocol handler initialized\n");
236 	return 0;
237 }
238 
239 static void __exit ir_sharp_decode_exit(void)
240 {
241 	ir_raw_handler_unregister(&sharp_handler);
242 }
243 
244 module_init(ir_sharp_decode_init);
245 module_exit(ir_sharp_decode_exit);
246 
247 MODULE_LICENSE("GPL");
248 MODULE_AUTHOR("James Hogan <jhogan@kernel.org>");
249 MODULE_DESCRIPTION("Sharp IR protocol decoder");
250