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		  136000 /* ns */
16 #define XMP_LEADER		  210000 /* ns */
17 #define XMP_NIBBLE_PREFIX	  760000 /* ns */
18 #define	XMP_HALFFRAME_SPACE	13800000 /* ns */
19 #define	XMP_TRAILER_SPACE	20000000 /* should be 80ms but not all dureation supliers can go that high */
20 
21 enum xmp_state {
22 	STATE_INACTIVE,
23 	STATE_LEADER_PULSE,
24 	STATE_NIBBLE_SPACE,
25 };
26 
27 /**
28  * ir_xmp_decode() - Decode one XMP pulse or space
29  * @dev:	the struct rc_dev descriptor of the device
30  * @ev:		the struct ir_raw_event descriptor of the pulse/space
31  *
32  * This function returns -EINVAL if the pulse violates the state machine
33  */
34 static int ir_xmp_decode(struct rc_dev *dev, struct ir_raw_event ev)
35 {
36 	struct xmp_dec *data = &dev->raw->xmp;
37 
38 	if (!is_timing_event(ev)) {
39 		if (ev.reset)
40 			data->state = STATE_INACTIVE;
41 		return 0;
42 	}
43 
44 	dev_dbg(&dev->dev, "XMP decode started at state %d %d (%uus %s)\n",
45 		data->state, data->count, TO_US(ev.duration), TO_STR(ev.pulse));
46 
47 	switch (data->state) {
48 
49 	case STATE_INACTIVE:
50 		if (!ev.pulse)
51 			break;
52 
53 		if (eq_margin(ev.duration, XMP_LEADER, XMP_UNIT / 2)) {
54 			data->count = 0;
55 			data->state = STATE_NIBBLE_SPACE;
56 		}
57 
58 		return 0;
59 
60 	case STATE_LEADER_PULSE:
61 		if (!ev.pulse)
62 			break;
63 
64 		if (eq_margin(ev.duration, XMP_LEADER, XMP_UNIT / 2))
65 			data->state = STATE_NIBBLE_SPACE;
66 
67 		return 0;
68 
69 	case STATE_NIBBLE_SPACE:
70 		if (ev.pulse)
71 			break;
72 
73 		if (geq_margin(ev.duration, XMP_TRAILER_SPACE, XMP_NIBBLE_PREFIX)) {
74 			int divider, i;
75 			u8 addr, subaddr, subaddr2, toggle, oem, obc1, obc2, sum1, sum2;
76 			u32 *n;
77 			u32 scancode;
78 
79 			if (data->count != 16) {
80 				dev_dbg(&dev->dev, "received TRAILER period at index %d: %u\n",
81 					data->count, ev.duration);
82 				data->state = STATE_INACTIVE;
83 				return -EINVAL;
84 			}
85 
86 			n = data->durations;
87 			/*
88 			 * the 4th nibble should be 15 so base the divider on this
89 			 * to transform durations into nibbles. Subtract 2000 from
90 			 * the divider to compensate for fluctuations in the signal
91 			 */
92 			divider = (n[3] - XMP_NIBBLE_PREFIX) / 15 - 2000;
93 			if (divider < 50) {
94 				dev_dbg(&dev->dev, "divider to small %d.\n",
95 					divider);
96 				data->state = STATE_INACTIVE;
97 				return -EINVAL;
98 			}
99 
100 			/* convert to nibbles and do some sanity checks */
101 			for (i = 0; i < 16; i++)
102 				n[i] = (n[i] - XMP_NIBBLE_PREFIX) / divider;
103 			sum1 = (15 + n[0] + n[1] + n[2] + n[3] +
104 				n[4] + n[5] + n[6] + n[7]) % 16;
105 			sum2 = (15 + n[8] + n[9] + n[10] + n[11] +
106 				n[12] + n[13] + n[14] + n[15]) % 16;
107 
108 			if (sum1 != 15 || sum2 != 15) {
109 				dev_dbg(&dev->dev, "checksum errors sum1=0x%X sum2=0x%X\n",
110 					sum1, sum2);
111 				data->state = STATE_INACTIVE;
112 				return -EINVAL;
113 			}
114 
115 			subaddr  = n[0] << 4 | n[2];
116 			subaddr2 = n[8] << 4 | n[11];
117 			oem      = n[4] << 4 | n[5];
118 			addr     = n[6] << 4 | n[7];
119 			toggle   = n[10];
120 			obc1 = n[12] << 4 | n[13];
121 			obc2 = n[14] << 4 | n[15];
122 			if (subaddr != subaddr2) {
123 				dev_dbg(&dev->dev, "subaddress nibbles mismatch 0x%02X != 0x%02X\n",
124 					subaddr, subaddr2);
125 				data->state = STATE_INACTIVE;
126 				return -EINVAL;
127 			}
128 			if (oem != 0x44)
129 				dev_dbg(&dev->dev, "Warning: OEM nibbles 0x%02X. Expected 0x44\n",
130 					oem);
131 
132 			scancode = addr << 24 | subaddr << 16 |
133 				   obc1 << 8 | obc2;
134 			dev_dbg(&dev->dev, "XMP scancode 0x%06x\n", scancode);
135 
136 			if (toggle == 0) {
137 				rc_keydown(dev, RC_PROTO_XMP, scancode, 0);
138 			} else {
139 				rc_repeat(dev);
140 				dev_dbg(&dev->dev, "Repeat last key\n");
141 			}
142 			data->state = STATE_INACTIVE;
143 
144 			return 0;
145 
146 		} else if (geq_margin(ev.duration, XMP_HALFFRAME_SPACE, XMP_NIBBLE_PREFIX)) {
147 			/* Expect 8 or 16 nibble pulses. 16 in case of 'final' frame */
148 			if (data->count == 16) {
149 				dev_dbg(&dev->dev, "received half frame pulse at index %d. Probably a final frame key-up event: %u\n",
150 					data->count, ev.duration);
151 				/*
152 				 * TODO: for now go back to half frame position
153 				 *	 so trailer can be found and key press
154 				 *	 can be handled.
155 				 */
156 				data->count = 8;
157 			}
158 
159 			else if (data->count != 8)
160 				dev_dbg(&dev->dev, "received half frame pulse at index %d: %u\n",
161 					data->count, ev.duration);
162 			data->state = STATE_LEADER_PULSE;
163 
164 			return 0;
165 
166 		} else if (geq_margin(ev.duration, XMP_NIBBLE_PREFIX, XMP_UNIT)) {
167 			/* store nibble raw data, decode after trailer */
168 			if (data->count == 16) {
169 				dev_dbg(&dev->dev, "to many pulses (%d) ignoring: %u\n",
170 					data->count, ev.duration);
171 				data->state = STATE_INACTIVE;
172 				return -EINVAL;
173 			}
174 			data->durations[data->count] = ev.duration;
175 			data->count++;
176 			data->state = STATE_LEADER_PULSE;
177 
178 			return 0;
179 
180 		}
181 
182 		break;
183 	}
184 
185 	dev_dbg(&dev->dev, "XMP decode failed at count %d state %d (%uus %s)\n",
186 		data->count, data->state, TO_US(ev.duration), TO_STR(ev.pulse));
187 	data->state = STATE_INACTIVE;
188 	return -EINVAL;
189 }
190 
191 static struct ir_raw_handler xmp_handler = {
192 	.protocols	= RC_PROTO_BIT_XMP,
193 	.decode		= ir_xmp_decode,
194 	.min_timeout	= XMP_TRAILER_SPACE,
195 };
196 
197 static int __init ir_xmp_decode_init(void)
198 {
199 	ir_raw_handler_register(&xmp_handler);
200 
201 	printk(KERN_INFO "IR XMP protocol handler initialized\n");
202 	return 0;
203 }
204 
205 static void __exit ir_xmp_decode_exit(void)
206 {
207 	ir_raw_handler_unregister(&xmp_handler);
208 }
209 
210 module_init(ir_xmp_decode_init);
211 module_exit(ir_xmp_decode_exit);
212 
213 MODULE_LICENSE("GPL");
214 MODULE_AUTHOR("Marcel Mol <marcel@mesa.nl>");
215 MODULE_AUTHOR("MESA Consulting (http://www.mesa.nl)");
216 MODULE_DESCRIPTION("XMP IR protocol decoder");
217