1 /*
2 * Copyright (c) 2014 The DragonFly Project. All rights reserved.
3 *
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
34 *------------------------------------------------------------------------------
35 * Copyright 2011 Atmel Corporation. All rights reserved.
36 *
37 * Redistribution and use in source and binary forms, with or without
38 * modification, are permitted provided that the following conditions are met:
39 *
40 * 1. Redistributions of source code must retain the above copyright notice,
41 * this list of conditions and the following disclaimer.
42 *
43 * 2. Redistributions in binary form must reproduce the above copyright
44 * notice, this list of conditions and the following disclaimer in the
45 * documentation and/or other materials provided with the distribution.
46 *
47 * THIS SOFTWARE IS PROVIDED BY ATMEL ''AS IS'' AND ANY EXPRESS OR IMPLIED
48 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
49 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
50 * EVENT SHALL ATMEL OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
51 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
52 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
53 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
54 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
55 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
56 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
57 *-----------------------------------------------------------------------------
58 */
59 /*
60 * This file contains a mix of code taken from the atmel-maxtouch/obp-utils
61 * github codebase and my own for testing the atmel touchscreen chipset in
62 * the Acer C720P chromebook.
63 *
64 * This code is independent and is used by both kernel AND user mode programs.
65 */
66
67 #include <sys/types.h>
68
69 #include "obp-utils.h"
70
71 /*!
72 * @brief Information block checksum return function.
73 * @return 24-bit checksum value in 32-bit integer.
74 */
75 uint32_t
obp_convert_crc(struct mxt_raw_crc * crc)76 obp_convert_crc(struct mxt_raw_crc *crc)
77 {
78 return ((crc->CRC_hi<<16u) | (crc->CRC));
79 }
80
81 /*!
82 * @brief Information Block Checksum algorithm.
83 * @return Calculated Information Block Checksum.
84 */
85 static
86 uint32_t
crc24_2byte(uint32_t crc,uint8_t firstbyte,uint8_t secondbyte)87 crc24_2byte(uint32_t crc, uint8_t firstbyte, uint8_t secondbyte)
88 {
89 static const uint32_t CRCPOLY = 0x0080001B;
90 uint32_t result;
91 uint16_t data_word;
92
93 data_word = (uint16_t) ((uint16_t)(secondbyte << 8u) | firstbyte);
94 result = ((crc << 1u) ^ (uint32_t)data_word);
95
96 /* Check if 25th bit is set, and XOR the result to create
97 * 24-bit checksum */
98 if (result & 0x1000000) {
99 result ^= CRCPOLY;
100 }
101 return result;
102 }
103
104 /*
105 * Return 24-bit crc.
106 */
107 uint32_t
obp_crc24(uint8_t * buf,size_t bytes)108 obp_crc24(uint8_t *buf, size_t bytes)
109 {
110 uint32_t crc;
111 size_t i;
112
113 crc = 0;
114 for (i = 0; i < (bytes & ~1); i += 2) {
115 crc = crc24_2byte(crc, buf[i], buf[i+1]);
116 }
117 if (i < bytes)
118 crc = crc24_2byte(crc, buf[i], 0);
119 crc &= 0x00FFFFFF;
120
121 return crc;
122 }
123