/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * SN9C2028 common functions
 *
 * Copyright (C) 2009 Theodore Kilgore <kilgota@auburn,edu>
 *
 * Based closely upon the file gspca/pac_common.h
 */

static const unsigned char sn9c2028_sof_marker[] = {
        0xff, 0xff, 0x00, 0xc4, 0xc4, 0x96,
        0x00,
        0x00, /* seq */
        0x00,
        0x00,
        0x00, /* avg luminance lower 8 bit */
        0x00, /* avg luminance higher 8 bit */
};

static unsigned char *sn9c2028_find_sof(struct gspca_dev *gspca_dev,
                                        unsigned char *m, int len)
{
        struct sd *sd = (struct sd *) gspca_dev;
        int i;

        /* Search for the SOF marker (fixed part) in the header */
        for (i = 0; i < len; i++) {
                if ((m[i] == sn9c2028_sof_marker[sd->sof_read]) ||
                    (sd->sof_read > 5)) {
                        sd->sof_read++;
                        if (sd->sof_read == 11)
                                sd->avg_lum_l = m[i];
                        if (sd->sof_read == 12)
                                sd->avg_lum = (m[i] << 8) + sd->avg_lum_l;
                        if (sd->sof_read == sizeof(sn9c2028_sof_marker)) {
                                gspca_dbg(gspca_dev, D_FRAM,
                                          "SOF found, bytes to analyze: %u - Frame starts at byte #%u\n",
                                          len, i + 1);
                                sd->sof_read = 0;
                                return m + i + 1;
                        }
                } else {
                        sd->sof_read = 0;
                }
        }

        return NULL;
}