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 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 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 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