| Kyle Swenson | 8d8f654 | 2021-03-15 11:02:55 -0600 | [diff] [blame^] | 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 | } |