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
10static 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
20static 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}
49