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
ir_imon_decode_scancode(struct rc_dev * dev)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 */
ir_imon_decode(struct rc_dev * dev,struct ir_raw_event ev)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.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
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 */
ir_imon_encode(enum rc_proto protocol,u32 scancode,struct ir_raw_event * events,unsigned int max)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
ir_imon_register(struct rc_dev * dev)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
ir_imon_decode_init(void)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
ir_imon_decode_exit(void)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