drivers/media/usb/gspca/sn9c2028.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * SN9C2028 common functions
   4  *
   5  * Copyright (C) 2009 Theodore Kilgore <kilgota@auburn,edu>
   6  *
   7  * Based closely upon the file gspca/pac_common.h
   8  */
   9
  10 static const unsigned char sn9c2028_sof_marker[] = {
  11         0xff, 0xff, 0x00, 0xc4, 0xc4, 0x96,
  12         0x00,
  13         0x00, /* seq */
  14         0x00,
  15         0x00,
  16         0x00, /* avg luminance lower 8 bit */
  17         0x00, /* avg luminance higher 8 bit */
  18 };
  19
  20 static unsigned char *sn9c2028_find_sof(struct gspca_dev *gspca_dev,
  21                                         unsigned char *m, int len)
  22 {
  23         struct sd *sd = (struct sd *) gspca_dev;
  24         int i;
  25
  26         /* Search for the SOF marker (fixed part) in the header */
  27         for (i = 0; i < len; i++) {
  28                 if ((m[i] == sn9c2028_sof_marker[sd->sof_read]) ||
  29                     (sd->sof_read > 5)) {
  30                         sd->sof_read++;
  31                         if (sd->sof_read == 11)
  32                                 sd->avg_lum_l = m[i];
  33                         if (sd->sof_read == 12)
  34                                 sd->avg_lum = (m[i] << 8) + sd->avg_lum_l;
  35                         if (sd->sof_read == sizeof(sn9c2028_sof_marker)) {
  36                                 gspca_dbg(gspca_dev, D_FRAM,
  37                                           "SOF found, bytes to analyze: %u - Frame starts at byte #%u\n",
  38                                           len, i + 1);
  39                                 sd->sof_read = 0;
  40                                 return m + i + 1;
  41                         }
  42                 } else {
  43                         sd->sof_read = 0;
  44                 }
  45         }
  46
  47         return NULL;
  48 }