1*4882a593Smuzhiyun /* SPDX-License-Identifier: GPL-2.0-or-later */
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * Pixart PAC207BCA / PAC73xx common functions
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * Copyright (C) 2008 Hans de Goede <j.w.r.degoede@hhs.nl>
6*4882a593Smuzhiyun * Copyright (C) 2005 Thomas Kaiser thomas@kaiser-linux.li
7*4882a593Smuzhiyun * Copyleft (C) 2005 Michel Xhaard mxhaard@magic.fr
8*4882a593Smuzhiyun *
9*4882a593Smuzhiyun * V4L2 by Jean-Francois Moine <http://moinejf.free.fr>
10*4882a593Smuzhiyun */
11*4882a593Smuzhiyun
12*4882a593Smuzhiyun /* We calculate the autogain at the end of the transfer of a frame, at this
13*4882a593Smuzhiyun moment a frame with the old settings is being captured and transmitted. So
14*4882a593Smuzhiyun if we adjust the gain or exposure we must ignore at least the next frame for
15*4882a593Smuzhiyun the new settings to come into effect before doing any other adjustments. */
16*4882a593Smuzhiyun #define PAC_AUTOGAIN_IGNORE_FRAMES 2
17*4882a593Smuzhiyun
18*4882a593Smuzhiyun static const unsigned char pac_sof_marker[5] =
19*4882a593Smuzhiyun { 0xff, 0xff, 0x00, 0xff, 0x96 };
20*4882a593Smuzhiyun
21*4882a593Smuzhiyun /*
22*4882a593Smuzhiyun The following state machine finds the SOF marker sequence
23*4882a593Smuzhiyun 0xff, 0xff, 0x00, 0xff, 0x96 in a byte stream.
24*4882a593Smuzhiyun
25*4882a593Smuzhiyun +----------+
26*4882a593Smuzhiyun | 0: START |<---------------\
27*4882a593Smuzhiyun +----------+<-\ |
28*4882a593Smuzhiyun | \---/otherwise |
29*4882a593Smuzhiyun v 0xff |
30*4882a593Smuzhiyun +----------+ otherwise |
31*4882a593Smuzhiyun | 1 |--------------->*
32*4882a593Smuzhiyun | | ^
33*4882a593Smuzhiyun +----------+ |
34*4882a593Smuzhiyun | |
35*4882a593Smuzhiyun v 0xff |
36*4882a593Smuzhiyun +----------+<-\0xff |
37*4882a593Smuzhiyun /->| |--/ |
38*4882a593Smuzhiyun | | 2 |--------------->*
39*4882a593Smuzhiyun | | | otherwise ^
40*4882a593Smuzhiyun | +----------+ |
41*4882a593Smuzhiyun | | |
42*4882a593Smuzhiyun | v 0x00 |
43*4882a593Smuzhiyun | +----------+ |
44*4882a593Smuzhiyun | | 3 | |
45*4882a593Smuzhiyun | | |--------------->*
46*4882a593Smuzhiyun | +----------+ otherwise ^
47*4882a593Smuzhiyun | | |
48*4882a593Smuzhiyun 0xff | v 0xff |
49*4882a593Smuzhiyun | +----------+ |
50*4882a593Smuzhiyun \--| 4 | |
51*4882a593Smuzhiyun | |----------------/
52*4882a593Smuzhiyun +----------+ otherwise
53*4882a593Smuzhiyun |
54*4882a593Smuzhiyun v 0x96
55*4882a593Smuzhiyun +----------+
56*4882a593Smuzhiyun | FOUND |
57*4882a593Smuzhiyun +----------+
58*4882a593Smuzhiyun */
59*4882a593Smuzhiyun
pac_find_sof(struct gspca_dev * gspca_dev,u8 * sof_read,unsigned char * m,int len)60*4882a593Smuzhiyun static unsigned char *pac_find_sof(struct gspca_dev *gspca_dev, u8 *sof_read,
61*4882a593Smuzhiyun unsigned char *m, int len)
62*4882a593Smuzhiyun {
63*4882a593Smuzhiyun int i;
64*4882a593Smuzhiyun
65*4882a593Smuzhiyun /* Search for the SOF marker (fixed part) in the header */
66*4882a593Smuzhiyun for (i = 0; i < len; i++) {
67*4882a593Smuzhiyun switch (*sof_read) {
68*4882a593Smuzhiyun case 0:
69*4882a593Smuzhiyun if (m[i] == 0xff)
70*4882a593Smuzhiyun *sof_read = 1;
71*4882a593Smuzhiyun break;
72*4882a593Smuzhiyun case 1:
73*4882a593Smuzhiyun if (m[i] == 0xff)
74*4882a593Smuzhiyun *sof_read = 2;
75*4882a593Smuzhiyun else
76*4882a593Smuzhiyun *sof_read = 0;
77*4882a593Smuzhiyun break;
78*4882a593Smuzhiyun case 2:
79*4882a593Smuzhiyun switch (m[i]) {
80*4882a593Smuzhiyun case 0x00:
81*4882a593Smuzhiyun *sof_read = 3;
82*4882a593Smuzhiyun break;
83*4882a593Smuzhiyun case 0xff:
84*4882a593Smuzhiyun /* stay in this state */
85*4882a593Smuzhiyun break;
86*4882a593Smuzhiyun default:
87*4882a593Smuzhiyun *sof_read = 0;
88*4882a593Smuzhiyun }
89*4882a593Smuzhiyun break;
90*4882a593Smuzhiyun case 3:
91*4882a593Smuzhiyun if (m[i] == 0xff)
92*4882a593Smuzhiyun *sof_read = 4;
93*4882a593Smuzhiyun else
94*4882a593Smuzhiyun *sof_read = 0;
95*4882a593Smuzhiyun break;
96*4882a593Smuzhiyun case 4:
97*4882a593Smuzhiyun switch (m[i]) {
98*4882a593Smuzhiyun case 0x96:
99*4882a593Smuzhiyun /* Pattern found */
100*4882a593Smuzhiyun gspca_dbg(gspca_dev, D_FRAM,
101*4882a593Smuzhiyun "SOF found, bytes to analyze: %u - Frame starts at byte #%u\n",
102*4882a593Smuzhiyun len, i + 1);
103*4882a593Smuzhiyun *sof_read = 0;
104*4882a593Smuzhiyun return m + i + 1;
105*4882a593Smuzhiyun break;
106*4882a593Smuzhiyun case 0xff:
107*4882a593Smuzhiyun *sof_read = 2;
108*4882a593Smuzhiyun break;
109*4882a593Smuzhiyun default:
110*4882a593Smuzhiyun *sof_read = 0;
111*4882a593Smuzhiyun }
112*4882a593Smuzhiyun break;
113*4882a593Smuzhiyun default:
114*4882a593Smuzhiyun *sof_read = 0;
115*4882a593Smuzhiyun }
116*4882a593Smuzhiyun }
117*4882a593Smuzhiyun
118*4882a593Smuzhiyun return NULL;
119*4882a593Smuzhiyun }
120