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 */
30enum imon_state {
31	STATE_INACTIVE,
32	STATE_BIT_CHK,
33	STATE_BIT_START,
34	STATE_FINISHED,
35	STATE_ERROR,
36};
37
38static 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 */
93static 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.overflow)
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
168err_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 */
190static 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
231static 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
240static 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
249static 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
257static void __exit ir_imon_decode_exit(void)
258{
259	ir_raw_handler_unregister(&imon_handler);
260}
261
262module_init(ir_imon_decode_init);
263module_exit(ir_imon_decode_exit);
264
265MODULE_LICENSE("GPL");
266MODULE_AUTHOR("Sean Young <sean@mess.org>");
267MODULE_DESCRIPTION("iMON IR protocol decoder");
268