cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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ir-xmp-decoder.c (5727B)


      1// SPDX-License-Identifier: GPL-2.0-only
      2/* ir-xmp-decoder.c - handle XMP IR Pulse/Space protocol
      3 *
      4 * Copyright (C) 2014 by Marcel Mol
      5 *
      6 * - Based on info from http://www.hifi-remote.com
      7 * - Ignore Toggle=9 frames
      8 * - Ignore XMP-1 XMP-2 difference, always store 16 bit OBC
      9 */
     10
     11#include <linux/bitrev.h>
     12#include <linux/module.h>
     13#include "rc-core-priv.h"
     14
     15#define XMP_UNIT		  136 /* us */
     16#define XMP_LEADER		  210 /* us */
     17#define XMP_NIBBLE_PREFIX	  760 /* us */
     18#define	XMP_HALFFRAME_SPACE	13800 /* us */
     19/* should be 80ms but not all duration supliers can go that high */
     20#define	XMP_TRAILER_SPACE	20000
     21
     22enum xmp_state {
     23	STATE_INACTIVE,
     24	STATE_LEADER_PULSE,
     25	STATE_NIBBLE_SPACE,
     26};
     27
     28/**
     29 * ir_xmp_decode() - Decode one XMP pulse or space
     30 * @dev:	the struct rc_dev descriptor of the device
     31 * @ev:		the struct ir_raw_event descriptor of the pulse/space
     32 *
     33 * This function returns -EINVAL if the pulse violates the state machine
     34 */
     35static int ir_xmp_decode(struct rc_dev *dev, struct ir_raw_event ev)
     36{
     37	struct xmp_dec *data = &dev->raw->xmp;
     38
     39	if (!is_timing_event(ev)) {
     40		if (ev.overflow)
     41			data->state = STATE_INACTIVE;
     42		return 0;
     43	}
     44
     45	dev_dbg(&dev->dev, "XMP decode started at state %d %d (%uus %s)\n",
     46		data->state, data->count, ev.duration, TO_STR(ev.pulse));
     47
     48	switch (data->state) {
     49
     50	case STATE_INACTIVE:
     51		if (!ev.pulse)
     52			break;
     53
     54		if (eq_margin(ev.duration, XMP_LEADER, XMP_UNIT / 2)) {
     55			data->count = 0;
     56			data->state = STATE_NIBBLE_SPACE;
     57		}
     58
     59		return 0;
     60
     61	case STATE_LEADER_PULSE:
     62		if (!ev.pulse)
     63			break;
     64
     65		if (eq_margin(ev.duration, XMP_LEADER, XMP_UNIT / 2))
     66			data->state = STATE_NIBBLE_SPACE;
     67
     68		return 0;
     69
     70	case STATE_NIBBLE_SPACE:
     71		if (ev.pulse)
     72			break;
     73
     74		if (geq_margin(ev.duration, XMP_TRAILER_SPACE, XMP_NIBBLE_PREFIX)) {
     75			int divider, i;
     76			u8 addr, subaddr, subaddr2, toggle, oem, obc1, obc2, sum1, sum2;
     77			u32 *n;
     78			u32 scancode;
     79
     80			if (data->count != 16) {
     81				dev_dbg(&dev->dev, "received TRAILER period at index %d: %u\n",
     82					data->count, ev.duration);
     83				data->state = STATE_INACTIVE;
     84				return -EINVAL;
     85			}
     86
     87			n = data->durations;
     88			/*
     89			 * the 4th nibble should be 15 so base the divider on this
     90			 * to transform durations into nibbles. Subtract 2000 from
     91			 * the divider to compensate for fluctuations in the signal
     92			 */
     93			divider = (n[3] - XMP_NIBBLE_PREFIX) / 15 - 2000;
     94			if (divider < 50) {
     95				dev_dbg(&dev->dev, "divider to small %d.\n",
     96					divider);
     97				data->state = STATE_INACTIVE;
     98				return -EINVAL;
     99			}
    100
    101			/* convert to nibbles and do some sanity checks */
    102			for (i = 0; i < 16; i++)
    103				n[i] = (n[i] - XMP_NIBBLE_PREFIX) / divider;
    104			sum1 = (15 + n[0] + n[1] + n[2] + n[3] +
    105				n[4] + n[5] + n[6] + n[7]) % 16;
    106			sum2 = (15 + n[8] + n[9] + n[10] + n[11] +
    107				n[12] + n[13] + n[14] + n[15]) % 16;
    108
    109			if (sum1 != 15 || sum2 != 15) {
    110				dev_dbg(&dev->dev, "checksum errors sum1=0x%X sum2=0x%X\n",
    111					sum1, sum2);
    112				data->state = STATE_INACTIVE;
    113				return -EINVAL;
    114			}
    115
    116			subaddr  = n[0] << 4 | n[2];
    117			subaddr2 = n[8] << 4 | n[11];
    118			oem      = n[4] << 4 | n[5];
    119			addr     = n[6] << 4 | n[7];
    120			toggle   = n[10];
    121			obc1 = n[12] << 4 | n[13];
    122			obc2 = n[14] << 4 | n[15];
    123			if (subaddr != subaddr2) {
    124				dev_dbg(&dev->dev, "subaddress nibbles mismatch 0x%02X != 0x%02X\n",
    125					subaddr, subaddr2);
    126				data->state = STATE_INACTIVE;
    127				return -EINVAL;
    128			}
    129			if (oem != 0x44)
    130				dev_dbg(&dev->dev, "Warning: OEM nibbles 0x%02X. Expected 0x44\n",
    131					oem);
    132
    133			scancode = addr << 24 | subaddr << 16 |
    134				   obc1 << 8 | obc2;
    135			dev_dbg(&dev->dev, "XMP scancode 0x%06x\n", scancode);
    136
    137			if (toggle == 0) {
    138				rc_keydown(dev, RC_PROTO_XMP, scancode, 0);
    139			} else {
    140				rc_repeat(dev);
    141				dev_dbg(&dev->dev, "Repeat last key\n");
    142			}
    143			data->state = STATE_INACTIVE;
    144
    145			return 0;
    146
    147		} else if (geq_margin(ev.duration, XMP_HALFFRAME_SPACE, XMP_NIBBLE_PREFIX)) {
    148			/* Expect 8 or 16 nibble pulses. 16 in case of 'final' frame */
    149			if (data->count == 16) {
    150				dev_dbg(&dev->dev, "received half frame pulse at index %d. Probably a final frame key-up event: %u\n",
    151					data->count, ev.duration);
    152				/*
    153				 * TODO: for now go back to half frame position
    154				 *	 so trailer can be found and key press
    155				 *	 can be handled.
    156				 */
    157				data->count = 8;
    158			}
    159
    160			else if (data->count != 8)
    161				dev_dbg(&dev->dev, "received half frame pulse at index %d: %u\n",
    162					data->count, ev.duration);
    163			data->state = STATE_LEADER_PULSE;
    164
    165			return 0;
    166
    167		} else if (geq_margin(ev.duration, XMP_NIBBLE_PREFIX, XMP_UNIT)) {
    168			/* store nibble raw data, decode after trailer */
    169			if (data->count == 16) {
    170				dev_dbg(&dev->dev, "too many pulses (%d) ignoring: %u\n",
    171					data->count, ev.duration);
    172				data->state = STATE_INACTIVE;
    173				return -EINVAL;
    174			}
    175			data->durations[data->count] = ev.duration;
    176			data->count++;
    177			data->state = STATE_LEADER_PULSE;
    178
    179			return 0;
    180
    181		}
    182
    183		break;
    184	}
    185
    186	dev_dbg(&dev->dev, "XMP decode failed at count %d state %d (%uus %s)\n",
    187		data->count, data->state, ev.duration, TO_STR(ev.pulse));
    188	data->state = STATE_INACTIVE;
    189	return -EINVAL;
    190}
    191
    192static struct ir_raw_handler xmp_handler = {
    193	.protocols	= RC_PROTO_BIT_XMP,
    194	.decode		= ir_xmp_decode,
    195	.min_timeout	= XMP_TRAILER_SPACE,
    196};
    197
    198static int __init ir_xmp_decode_init(void)
    199{
    200	ir_raw_handler_register(&xmp_handler);
    201
    202	printk(KERN_INFO "IR XMP protocol handler initialized\n");
    203	return 0;
    204}
    205
    206static void __exit ir_xmp_decode_exit(void)
    207{
    208	ir_raw_handler_unregister(&xmp_handler);
    209}
    210
    211module_init(ir_xmp_decode_init);
    212module_exit(ir_xmp_decode_exit);
    213
    214MODULE_LICENSE("GPL");
    215MODULE_AUTHOR("Marcel Mol <marcel@mesa.nl>");
    216MODULE_AUTHOR("MESA Consulting (http://www.mesa.nl)");
    217MODULE_DESCRIPTION("XMP IR protocol decoder");