1/* ir-rc6-decoder.c - A decoder for the RC6 IR protocol
2 *
3 * Copyright (C) 2010 by David Härdeman <david@hardeman.nu>
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 "rc-core-priv.h"
16#include <linux/module.h>
17
18/*
19 * This decoder currently supports:
20 * RC6-0-16	(standard toggle bit in header)
21 * RC6-6A-20	(no toggle bit)
22 * RC6-6A-24	(no toggle bit)
23 * RC6-6A-32	(MCE version with toggle bit in body)
24 */
25
26#define RC6_UNIT		444444	/* nanosecs */
27#define RC6_HEADER_NBITS	4	/* not including toggle bit */
28#define RC6_0_NBITS		16
29#define RC6_6A_32_NBITS		32
30#define RC6_6A_NBITS		128	/* Variable 8..128 */
31#define RC6_PREFIX_PULSE	(6 * RC6_UNIT)
32#define RC6_PREFIX_SPACE	(2 * RC6_UNIT)
33#define RC6_BIT_START		(1 * RC6_UNIT)
34#define RC6_BIT_END		(1 * RC6_UNIT)
35#define RC6_TOGGLE_START	(2 * RC6_UNIT)
36#define RC6_TOGGLE_END		(2 * RC6_UNIT)
37#define RC6_SUFFIX_SPACE	(6 * RC6_UNIT)
38#define RC6_MODE_MASK		0x07	/* for the header bits */
39#define RC6_STARTBIT_MASK	0x08	/* for the header bits */
40#define RC6_6A_MCE_TOGGLE_MASK	0x8000	/* for the body bits */
41#define RC6_6A_LCC_MASK		0xffff0000 /* RC6-6A-32 long customer code mask */
42#define RC6_6A_MCE_CC		0x800f0000 /* MCE customer code */
43#ifndef CHAR_BIT
44#define CHAR_BIT 8	/* Normally in <limits.h> */
45#endif
46
47enum rc6_mode {
48	RC6_MODE_0,
49	RC6_MODE_6A,
50	RC6_MODE_UNKNOWN,
51};
52
53enum rc6_state {
54	STATE_INACTIVE,
55	STATE_PREFIX_SPACE,
56	STATE_HEADER_BIT_START,
57	STATE_HEADER_BIT_END,
58	STATE_TOGGLE_START,
59	STATE_TOGGLE_END,
60	STATE_BODY_BIT_START,
61	STATE_BODY_BIT_END,
62	STATE_FINISHED,
63};
64
65static enum rc6_mode rc6_mode(struct rc6_dec *data)
66{
67	switch (data->header & RC6_MODE_MASK) {
68	case 0:
69		return RC6_MODE_0;
70	case 6:
71		if (!data->toggle)
72			return RC6_MODE_6A;
73		/* fall through */
74	default:
75		return RC6_MODE_UNKNOWN;
76	}
77}
78
79/**
80 * ir_rc6_decode() - Decode one RC6 pulse or space
81 * @dev:	the struct rc_dev descriptor of the device
82 * @ev:		the struct ir_raw_event descriptor of the pulse/space
83 *
84 * This function returns -EINVAL if the pulse violates the state machine
85 */
86static int ir_rc6_decode(struct rc_dev *dev, struct ir_raw_event ev)
87{
88	struct rc6_dec *data = &dev->raw->rc6;
89	u32 scancode;
90	u8 toggle;
91	enum rc_type protocol;
92
93	if (!(dev->enabled_protocols &
94	      (RC_BIT_RC6_0 | RC_BIT_RC6_6A_20 | RC_BIT_RC6_6A_24 |
95	       RC_BIT_RC6_6A_32 | RC_BIT_RC6_MCE)))
96		return 0;
97
98	if (!is_timing_event(ev)) {
99		if (ev.reset)
100			data->state = STATE_INACTIVE;
101		return 0;
102	}
103
104	if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
105		goto out;
106
107again:
108	IR_dprintk(2, "RC6 decode started at state %i (%uus %s)\n",
109		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
110
111	if (!geq_margin(ev.duration, RC6_UNIT, RC6_UNIT / 2))
112		return 0;
113
114	switch (data->state) {
115
116	case STATE_INACTIVE:
117		if (!ev.pulse)
118			break;
119
120		/* Note: larger margin on first pulse since each RC6_UNIT
121		   is quite short and some hardware takes some time to
122		   adjust to the signal */
123		if (!eq_margin(ev.duration, RC6_PREFIX_PULSE, RC6_UNIT))
124			break;
125
126		data->state = STATE_PREFIX_SPACE;
127		data->count = 0;
128		return 0;
129
130	case STATE_PREFIX_SPACE:
131		if (ev.pulse)
132			break;
133
134		if (!eq_margin(ev.duration, RC6_PREFIX_SPACE, RC6_UNIT / 2))
135			break;
136
137		data->state = STATE_HEADER_BIT_START;
138		data->header = 0;
139		return 0;
140
141	case STATE_HEADER_BIT_START:
142		if (!eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2))
143			break;
144
145		data->header <<= 1;
146		if (ev.pulse)
147			data->header |= 1;
148		data->count++;
149		data->state = STATE_HEADER_BIT_END;
150		return 0;
151
152	case STATE_HEADER_BIT_END:
153		if (!is_transition(&ev, &dev->raw->prev_ev))
154			break;
155
156		if (data->count == RC6_HEADER_NBITS)
157			data->state = STATE_TOGGLE_START;
158		else
159			data->state = STATE_HEADER_BIT_START;
160
161		decrease_duration(&ev, RC6_BIT_END);
162		goto again;
163
164	case STATE_TOGGLE_START:
165		if (!eq_margin(ev.duration, RC6_TOGGLE_START, RC6_UNIT / 2))
166			break;
167
168		data->toggle = ev.pulse;
169		data->state = STATE_TOGGLE_END;
170		return 0;
171
172	case STATE_TOGGLE_END:
173		if (!is_transition(&ev, &dev->raw->prev_ev) ||
174		    !geq_margin(ev.duration, RC6_TOGGLE_END, RC6_UNIT / 2))
175			break;
176
177		if (!(data->header & RC6_STARTBIT_MASK)) {
178			IR_dprintk(1, "RC6 invalid start bit\n");
179			break;
180		}
181
182		data->state = STATE_BODY_BIT_START;
183		decrease_duration(&ev, RC6_TOGGLE_END);
184		data->count = 0;
185		data->body = 0;
186
187		switch (rc6_mode(data)) {
188		case RC6_MODE_0:
189			data->wanted_bits = RC6_0_NBITS;
190			break;
191		case RC6_MODE_6A:
192			data->wanted_bits = RC6_6A_NBITS;
193			break;
194		default:
195			IR_dprintk(1, "RC6 unknown mode\n");
196			goto out;
197		}
198		goto again;
199
200	case STATE_BODY_BIT_START:
201		if (eq_margin(ev.duration, RC6_BIT_START, RC6_UNIT / 2)) {
202			/* Discard LSB's that won't fit in data->body */
203			if (data->count++ < CHAR_BIT * sizeof data->body) {
204				data->body <<= 1;
205				if (ev.pulse)
206					data->body |= 1;
207			}
208			data->state = STATE_BODY_BIT_END;
209			return 0;
210		} else if (RC6_MODE_6A == rc6_mode(data) && !ev.pulse &&
211				geq_margin(ev.duration, RC6_SUFFIX_SPACE, RC6_UNIT / 2)) {
212			data->state = STATE_FINISHED;
213			goto again;
214		}
215		break;
216
217	case STATE_BODY_BIT_END:
218		if (!is_transition(&ev, &dev->raw->prev_ev))
219			break;
220
221		if (data->count == data->wanted_bits)
222			data->state = STATE_FINISHED;
223		else
224			data->state = STATE_BODY_BIT_START;
225
226		decrease_duration(&ev, RC6_BIT_END);
227		goto again;
228
229	case STATE_FINISHED:
230		if (ev.pulse)
231			break;
232
233		switch (rc6_mode(data)) {
234		case RC6_MODE_0:
235			scancode = data->body;
236			toggle = data->toggle;
237			protocol = RC_TYPE_RC6_0;
238			IR_dprintk(1, "RC6(0) scancode 0x%04x (toggle: %u)\n",
239				   scancode, toggle);
240			break;
241
242		case RC6_MODE_6A:
243			if (data->count > CHAR_BIT * sizeof data->body) {
244				IR_dprintk(1, "RC6 too many (%u) data bits\n",
245					data->count);
246				goto out;
247			}
248
249			scancode = data->body;
250			switch (data->count) {
251			case 20:
252				protocol = RC_TYPE_RC6_6A_20;
253				toggle = 0;
254				break;
255			case 24:
256				protocol = RC_BIT_RC6_6A_24;
257				toggle = 0;
258				break;
259			case 32:
260				if ((scancode & RC6_6A_LCC_MASK) == RC6_6A_MCE_CC) {
261					protocol = RC_TYPE_RC6_MCE;
262					toggle = !!(scancode & RC6_6A_MCE_TOGGLE_MASK);
263					scancode &= ~RC6_6A_MCE_TOGGLE_MASK;
264				} else {
265					protocol = RC_BIT_RC6_6A_32;
266					toggle = 0;
267				}
268				break;
269			default:
270				IR_dprintk(1, "RC6(6A) unsupported length\n");
271				goto out;
272			}
273
274			IR_dprintk(1, "RC6(6A) proto 0x%04x, scancode 0x%08x (toggle: %u)\n",
275				   protocol, scancode, toggle);
276			break;
277		default:
278			IR_dprintk(1, "RC6 unknown mode\n");
279			goto out;
280		}
281
282		rc_keydown(dev, protocol, scancode, toggle);
283		data->state = STATE_INACTIVE;
284		return 0;
285	}
286
287out:
288	IR_dprintk(1, "RC6 decode failed at state %i (%uus %s)\n",
289		   data->state, TO_US(ev.duration), TO_STR(ev.pulse));
290	data->state = STATE_INACTIVE;
291	return -EINVAL;
292}
293
294static struct ir_raw_handler rc6_handler = {
295	.protocols	= RC_BIT_RC6_0 | RC_BIT_RC6_6A_20 |
296			  RC_BIT_RC6_6A_24 | RC_BIT_RC6_6A_32 |
297			  RC_BIT_RC6_MCE,
298	.decode		= ir_rc6_decode,
299};
300
301static int __init ir_rc6_decode_init(void)
302{
303	ir_raw_handler_register(&rc6_handler);
304
305	printk(KERN_INFO "IR RC6 protocol handler initialized\n");
306	return 0;
307}
308
309static void __exit ir_rc6_decode_exit(void)
310{
311	ir_raw_handler_unregister(&rc6_handler);
312}
313
314module_init(ir_rc6_decode_init);
315module_exit(ir_rc6_decode_exit);
316
317MODULE_LICENSE("GPL");
318MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
319MODULE_DESCRIPTION("RC6 IR protocol decoder");
320