LXR linux/drivers/media/rc/ir-imon-decoder.c

   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.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
 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