drivers/media/usb/gspca/sn9c2028.h

   1 /*
   2  * SN9C2028 common functions
   3  *
   4  * Copyright (C) 2009 Theodore Kilgore <kilgota@auburn,edu>
   5  *
   6  * Based closely upon the file gspca/pac_common.h
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  */
  19
  20 static const unsigned char sn9c2028_sof_marker[] = {
  21         0xff, 0xff, 0x00, 0xc4, 0xc4, 0x96,
  22         0x00,
  23         0x00, /* seq */
  24         0x00,
  25         0x00,
  26         0x00, /* avg luminance lower 8 bit */
  27         0x00, /* avg luminance higher 8 bit */
  28 };
  29
  30 static unsigned char *sn9c2028_find_sof(struct gspca_dev *gspca_dev,
  31                                         unsigned char *m, int len)
  32 {
  33         struct sd *sd = (struct sd *) gspca_dev;
  34         int i;
  35
  36         /* Search for the SOF marker (fixed part) in the header */
  37         for (i = 0; i < len; i++) {
  38                 if ((m[i] == sn9c2028_sof_marker[sd->sof_read]) ||
  39                     (sd->sof_read > 5)) {
  40                         sd->sof_read++;
  41                         if (sd->sof_read == 11)
  42                                 sd->avg_lum_l = m[i];
  43                         if (sd->sof_read == 12)
  44                                 sd->avg_lum = (m[i] << 8) + sd->avg_lum_l;
  45                         if (sd->sof_read == sizeof(sn9c2028_sof_marker)) {
  46                                 PDEBUG(D_FRAM,
  47                                         "SOF found, bytes to analyze: %u."
  48                                         " Frame starts at byte #%u",
  49                                         len, i + 1);
  50                                 sd->sof_read = 0;
  51                                 return m + i + 1;
  52                         }
  53                 } else {
  54                         sd->sof_read = 0;
  55                 }
  56         }
  57
  58         return NULL;
  59 }