drivers/media/video/gspca/pac_common.h

   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 transmitted, and a frame is
  28    being captured with the old settings. So if we adjust the autogain we must
  29    ignore atleast the 2 next frames for the new settings to come into effect
  30    before doing any other adjustments */
  31 #define PAC_AUTOGAIN_IGNORE_FRAMES      3
  32
  33 static const unsigned char pac_sof_marker[5] =
  34                 { 0xff, 0xff, 0x00, 0xff, 0x96 };
  35
  36 static unsigned char *pac_find_sof(struct gspca_dev *gspca_dev,
  37                                         unsigned char *m, int len)
  38 {
  39         struct sd *sd = (struct sd *) gspca_dev;
  40         int i;
  41
  42         /* Search for the SOF marker (fixed part) in the header */
  43         for (i = 0; i < len; i++) {
  44                 if (m[i] == pac_sof_marker[sd->sof_read]) {
  45                         sd->sof_read++;
  46                         if (sd->sof_read == sizeof(pac_sof_marker)) {
  47                                 PDEBUG(D_FRAM,
  48                                         "SOF found, bytes to analyze: %u."
  49                                         " Frame starts at byte #%u",
  50                                         len, i + 1);
  51                                 sd->sof_read = 0;
  52                                 return m + i + 1;
  53                         }
  54                 } else {
  55                         sd->sof_read = 0;
  56                 }
  57         }
  58
  59         return NULL;
  60 }