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 
22 enum 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  */
35 static 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.reset)
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 
192 static 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 
198 static 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 
206 static void __exit ir_xmp_decode_exit(void)
207 {
208 	ir_raw_handler_unregister(&xmp_handler);
209 }
210 
211 module_init(ir_xmp_decode_init);
212 module_exit(ir_xmp_decode_exit);
213 
214 MODULE_LICENSE("GPL");
215 MODULE_AUTHOR("Marcel Mol <marcel@mesa.nl>");
216 MODULE_AUTHOR("MESA Consulting (http://www.mesa.nl)");
217 MODULE_DESCRIPTION("XMP IR protocol decoder");
218