usb/gspca/sn9c2028.h

0001 /* SPDX-License-Identifier: GPL-2.0-or-later */
0002 /*
0003  * SN9C2028 common functions
0004  *
0005  * Copyright (C) 2009 Theodore Kilgore <kilgota@auburn,edu>
0006  *
0007  * Based closely upon the file gspca/pac_common.h
0008  */
0009
0010 static const unsigned char sn9c2028_sof_marker[] = {
0011     0xff, 0xff, 0x00, 0xc4, 0xc4, 0x96,
0012     0x00,
0013     0x00, /* seq */
0014     0x00,
0015     0x00,
0016     0x00, /* avg luminance lower 8 bit */
0017     0x00, /* avg luminance higher 8 bit */
0018 };
0019
0020 static unsigned char *sn9c2028_find_sof(struct gspca_dev *gspca_dev,
0021                     unsigned char *m, int len)
0022 {
0023     struct sd *sd = (struct sd *) gspca_dev;
0024     int i;
0025
0026     /* Search for the SOF marker (fixed part) in the header */
0027     for (i = 0; i < len; i++) {
0028         if ((m[i] == sn9c2028_sof_marker[sd->sof_read]) ||
0029             (sd->sof_read > 5)) {
0030             sd->sof_read++;
0031             if (sd->sof_read == 11)
0032                 sd->avg_lum_l = m[i];
0033             if (sd->sof_read == 12)
0034                 sd->avg_lum = (m[i] << 8) + sd->avg_lum_l;
0035             if (sd->sof_read == sizeof(sn9c2028_sof_marker)) {
0036                 gspca_dbg(gspca_dev, D_FRAM,
0037                       "SOF found, bytes to analyze: %u - Frame starts at byte #%u\n",
0038                       len, i + 1);
0039                 sd->sof_read = 0;
0040                 return m + i + 1;
0041             }
0042         } else {
0043             sd->sof_read = 0;
0044         }
0045     }
0046
0047     return NULL;
0048 }