1 // SPDX-License-Identifier: GPL-2.0+
2 // ir-imon-decoder.c - handle iMon protocol
3 //
4 // Copyright (C) 2018 by Sean Young <sean@mess.org>
5 
6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
7 
8 #include <linux/module.h>
9 #include "rc-core-priv.h"
10 
11 #define IMON_UNIT		416 /* us */
12 #define IMON_BITS		30
13 #define IMON_CHKBITS		(BIT(30) | BIT(25) | BIT(24) | BIT(22) | \
14 				 BIT(21) | BIT(20) | BIT(19) | BIT(18) | \
15 				 BIT(17) | BIT(16) | BIT(14) | BIT(13) | \
16 				 BIT(12) | BIT(11) | BIT(10) | BIT(9))
17 
18 /*
19  * This protocol has 30 bits. The format is one IMON_UNIT header pulse,
20  * followed by 30 bits. Each bit is one IMON_UNIT check field, and then
21  * one IMON_UNIT field with the actual bit (1=space, 0=pulse).
22  * The check field is always space for some bits, for others it is pulse if
23  * both the preceding and current bit are zero, else space. IMON_CHKBITS
24  * defines which bits are of type check.
25  *
26  * There is no way to distinguish an incomplete message from one where
27  * the lower bits are all set, iow. the last pulse is for the lowest
28  * bit which is 0.
29  */
30 enum imon_state {
31 	STATE_INACTIVE,
32 	STATE_BIT_CHK,
33 	STATE_BIT_START,
34 	STATE_FINISHED,
35 	STATE_ERROR,
36 };
37 
38 static void ir_imon_decode_scancode(struct rc_dev *dev)
39 {
40 	struct imon_dec *imon = &dev->raw->imon;
41 
42 	/* Keyboard/Mouse toggle */
43 	if (imon->bits == 0x299115b7)
44 		imon->stick_keyboard = !imon->stick_keyboard;
45 
46 	if ((imon->bits & 0xfc0000ff) == 0x680000b7) {
47 		int rel_x, rel_y;
48 		u8 buf;
49 
50 		buf = imon->bits >> 16;
51 		rel_x = (buf & 0x08) | (buf & 0x10) >> 2 |
52 			(buf & 0x20) >> 4 | (buf & 0x40) >> 6;
53 		if (imon->bits & 0x02000000)
54 			rel_x |= ~0x0f;
55 		buf = imon->bits >> 8;
56 		rel_y = (buf & 0x08) | (buf & 0x10) >> 2 |
57 			(buf & 0x20) >> 4 | (buf & 0x40) >> 6;
58 		if (imon->bits & 0x01000000)
59 			rel_y |= ~0x0f;
60 
61 		if (rel_x && rel_y && imon->stick_keyboard) {
62 			if (abs(rel_y) > abs(rel_x))
63 				imon->bits = rel_y > 0 ?
64 					0x289515b7 : /* KEY_DOWN */
65 					0x2aa515b7;  /* KEY_UP */
66 			else
67 				imon->bits = rel_x > 0 ?
68 					0x2ba515b7 : /* KEY_RIGHT */
69 					0x29a515b7;  /* KEY_LEFT */
70 		}
71 
72 		if (!imon->stick_keyboard) {
73 			input_report_rel(dev->input_dev, REL_X, rel_x);
74 			input_report_rel(dev->input_dev, REL_Y, rel_y);
75 
76 			input_report_key(dev->input_dev, BTN_LEFT,
77 					 (imon->bits & 0x00010000) != 0);
78 			input_report_key(dev->input_dev, BTN_RIGHT,
79 					 (imon->bits & 0x00040000) != 0);
80 		}
81 	}
82 
83 	rc_keydown(dev, RC_PROTO_IMON, imon->bits, 0);
84 }
85 
86 /**
87  * ir_imon_decode() - Decode one iMON pulse or space
88  * @dev:	the struct rc_dev descriptor of the device
89  * @ev:		the struct ir_raw_event descriptor of the pulse/space
90  *
91  * This function returns -EINVAL if the pulse violates the state machine
92  */
93 static int ir_imon_decode(struct rc_dev *dev, struct ir_raw_event ev)
94 {
95 	struct imon_dec *data = &dev->raw->imon;
96 
97 	if (!is_timing_event(ev)) {
98 		if (ev.reset)
99 			data->state = STATE_INACTIVE;
100 		return 0;
101 	}
102 
103 	dev_dbg(&dev->dev,
104 		"iMON decode started at state %d bitno %d (%uus %s)\n",
105 		data->state, data->count, ev.duration, TO_STR(ev.pulse));
106 
107 	/*
108 	 * Since iMON protocol is a series of bits, if at any point
109 	 * we encounter an error, make sure that any remaining bits
110 	 * aren't parsed as a scancode made up of less bits.
111 	 *
112 	 * Note that if the stick is held, then the remote repeats
113 	 * the scancode with about 12ms between them. So, make sure
114 	 * we have at least 10ms of space after an error. That way,
115 	 * we're at a new scancode.
116 	 */
117 	if (data->state == STATE_ERROR) {
118 		if (!ev.pulse && ev.duration > MS_TO_US(10))
119 			data->state = STATE_INACTIVE;
120 		return 0;
121 	}
122 
123 	for (;;) {
124 		if (!geq_margin(ev.duration, IMON_UNIT, IMON_UNIT / 2))
125 			return 0;
126 
127 		decrease_duration(&ev, IMON_UNIT);
128 
129 		switch (data->state) {
130 		case STATE_INACTIVE:
131 			if (ev.pulse) {
132 				data->state = STATE_BIT_CHK;
133 				data->bits = 0;
134 				data->count = IMON_BITS;
135 			}
136 			break;
137 		case STATE_BIT_CHK:
138 			if (IMON_CHKBITS & BIT(data->count))
139 				data->last_chk = ev.pulse;
140 			else if (ev.pulse)
141 				goto err_out;
142 			data->state = STATE_BIT_START;
143 			break;
144 		case STATE_BIT_START:
145 			data->bits <<= 1;
146 			if (!ev.pulse)
147 				data->bits |= 1;
148 
149 			if (IMON_CHKBITS & BIT(data->count)) {
150 				if (data->last_chk != !(data->bits & 3))
151 					goto err_out;
152 			}
153 
154 			if (!data->count--)
155 				data->state = STATE_FINISHED;
156 			else
157 				data->state = STATE_BIT_CHK;
158 			break;
159 		case STATE_FINISHED:
160 			if (ev.pulse)
161 				goto err_out;
162 			ir_imon_decode_scancode(dev);
163 			data->state = STATE_INACTIVE;
164 			break;
165 		}
166 	}
167 
168 err_out:
169 	dev_dbg(&dev->dev,
170 		"iMON decode failed at state %d bitno %d (%uus %s)\n",
171 		data->state, data->count, ev.duration, TO_STR(ev.pulse));
172 
173 	data->state = STATE_ERROR;
174 
175 	return -EINVAL;
176 }
177 
178 /**
179  * ir_imon_encode() - Encode a scancode as a stream of raw events
180  *
181  * @protocol:	protocol to encode
182  * @scancode:	scancode to encode
183  * @events:	array of raw ir events to write into
184  * @max:	maximum size of @events
185  *
186  * Returns:	The number of events written.
187  *		-ENOBUFS if there isn't enough space in the array to fit the
188  *		encoding. In this case all @max events will have been written.
189  */
190 static int ir_imon_encode(enum rc_proto protocol, u32 scancode,
191 			  struct ir_raw_event *events, unsigned int max)
192 {
193 	struct ir_raw_event *e = events;
194 	int i, pulse;
195 
196 	if (!max--)
197 		return -ENOBUFS;
198 	init_ir_raw_event_duration(e, 1, IMON_UNIT);
199 
200 	for (i = IMON_BITS; i >= 0; i--) {
201 		if (BIT(i) & IMON_CHKBITS)
202 			pulse = !(scancode & (BIT(i) | BIT(i + 1)));
203 		else
204 			pulse = 0;
205 
206 		if (pulse == e->pulse) {
207 			e->duration += IMON_UNIT;
208 		} else {
209 			if (!max--)
210 				return -ENOBUFS;
211 			init_ir_raw_event_duration(++e, pulse, IMON_UNIT);
212 		}
213 
214 		pulse = !(scancode & BIT(i));
215 
216 		if (pulse == e->pulse) {
217 			e->duration += IMON_UNIT;
218 		} else {
219 			if (!max--)
220 				return -ENOBUFS;
221 			init_ir_raw_event_duration(++e, pulse, IMON_UNIT);
222 		}
223 	}
224 
225 	if (e->pulse)
226 		e++;
227 
228 	return e - events;
229 }
230 
231 static int ir_imon_register(struct rc_dev *dev)
232 {
233 	struct imon_dec *imon = &dev->raw->imon;
234 
235 	imon->stick_keyboard = false;
236 
237 	return 0;
238 }
239 
240 static struct ir_raw_handler imon_handler = {
241 	.protocols	= RC_PROTO_BIT_IMON,
242 	.decode		= ir_imon_decode,
243 	.encode		= ir_imon_encode,
244 	.carrier	= 38000,
245 	.raw_register	= ir_imon_register,
246 	.min_timeout	= IMON_UNIT * IMON_BITS * 2,
247 };
248 
249 static int __init ir_imon_decode_init(void)
250 {
251 	ir_raw_handler_register(&imon_handler);
252 
253 	pr_info("IR iMON protocol handler initialized\n");
254 	return 0;
255 }
256 
257 static void __exit ir_imon_decode_exit(void)
258 {
259 	ir_raw_handler_unregister(&imon_handler);
260 }
261 
262 module_init(ir_imon_decode_init);
263 module_exit(ir_imon_decode_exit);
264 
265 MODULE_LICENSE("GPL");
266 MODULE_AUTHOR("Sean Young <sean@mess.org>");
267 MODULE_DESCRIPTION("iMON IR protocol decoder");
268