1 /* 2 * Pixart PAC207BCA / PAC73xx common functions 3 * 4 * Copyright (C) 2008 Hans de Goede <j.w.r.degoede@hhs.nl> 5 * Copyright (C) 2005 Thomas Kaiser thomas@kaiser-linux.li 6 * Copyleft (C) 2005 Michel Xhaard mxhaard@magic.fr 7 * 8 * V4L2 by Jean-Francois Moine <http://moinejf.free.fr> 9 * 10 * This program is free software; you can redistribute it and/or modify 11 * it under the terms of the GNU General Public License as published by 12 * the Free Software Foundation; either version 2 of the License, or 13 * (at your option) any later version. 14 * 15 * This program is distributed in the hope that it will be useful, 16 * but WITHOUT ANY WARRANTY; without even the implied warranty of 17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 18 * GNU General Public License for more details. 19 * 20 * You should have received a copy of the GNU General Public License 21 * along with this program; if not, write to the Free Software 22 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 23 * 24 */ 25 26 /* We calculate the autogain at the end of the transfer of a frame, at this 27 moment a frame with the old settings is being captured and transmitted. So 28 if we adjust the gain or exposure we must ignore atleast the next frame for 29 the new settings to come into effect before doing any other adjustments. */ 30 #define PAC_AUTOGAIN_IGNORE_FRAMES 2 31 32 static const unsigned char pac_sof_marker[5] = 33 { 0xff, 0xff, 0x00, 0xff, 0x96 }; 34 35 /* 36 The following state machine finds the SOF marker sequence 37 0xff, 0xff, 0x00, 0xff, 0x96 in a byte stream. 38 39 +----------+ 40 | 0: START |<---------------\ 41 +----------+<-\ | 42 | \---/otherwise | 43 v 0xff | 44 +----------+ otherwise | 45 | 1 |--------------->* 46 | | ^ 47 +----------+ | 48 | | 49 v 0xff | 50 +----------+<-\0xff | 51 /->| |--/ | 52 | | 2 |--------------->* 53 | | | otherwise ^ 54 | +----------+ | 55 | | | 56 | v 0x00 | 57 | +----------+ | 58 | | 3 | | 59 | | |--------------->* 60 | +----------+ otherwise ^ 61 | | | 62 0xff | v 0xff | 63 | +----------+ | 64 \--| 4 | | 65 | |----------------/ 66 +----------+ otherwise 67 | 68 v 0x96 69 +----------+ 70 | FOUND | 71 +----------+ 72 */ 73 74 static unsigned char *pac_find_sof(struct gspca_dev *gspca_dev, u8 *sof_read, 75 unsigned char *m, int len) 76 { 77 int i; 78 79 /* Search for the SOF marker (fixed part) in the header */ 80 for (i = 0; i < len; i++) { 81 switch (*sof_read) { 82 case 0: 83 if (m[i] == 0xff) 84 *sof_read = 1; 85 break; 86 case 1: 87 if (m[i] == 0xff) 88 *sof_read = 2; 89 else 90 *sof_read = 0; 91 break; 92 case 2: 93 switch (m[i]) { 94 case 0x00: 95 *sof_read = 3; 96 break; 97 case 0xff: 98 /* stay in this state */ 99 break; 100 default: 101 *sof_read = 0; 102 } 103 break; 104 case 3: 105 if (m[i] == 0xff) 106 *sof_read = 4; 107 else 108 *sof_read = 0; 109 break; 110 case 4: 111 switch (m[i]) { 112 case 0x96: 113 /* Pattern found */ 114 PDEBUG(D_FRAM, 115 "SOF found, bytes to analyze: %u." 116 " Frame starts at byte #%u", 117 len, i + 1); 118 *sof_read = 0; 119 return m + i + 1; 120 break; 121 case 0xff: 122 *sof_read = 2; 123 break; 124 default: 125 *sof_read = 0; 126 } 127 break; 128 default: 129 *sof_read = 0; 130 } 131 } 132 133 return NULL; 134 } 135