ir-xmp-decoder.c

  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");