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pac_common.h
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1 /*
2  * Pixart PAC207BCA / PAC73xx common functions
3  *
4  * Copyright (C) 2008 Hans de Goede <[email protected]>
5  * Copyright (C) 2005 Thomas Kaiser [email protected]
6  * Copyleft (C) 2005 Michel Xhaard [email protected]
7  *
8  * V4L2 by Jean-Francois Moine <http://moinejf.free.fr>
9  *
10  * This program is free software; you can redistribute it and/or modify
11  * it under the terms of the GNU General Public License as published by
12  * the Free Software Foundation; either version 2 of the License, or
13  * (at your option) any later version.
14  *
15  * This program is distributed in the hope that it will be useful,
16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18  * GNU General Public License for more details.
19  *
20  * You should have received a copy of the GNU General Public License
21  * along with this program; if not, write to the Free Software
22  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
23  *
24  */
25 
26 /* We calculate the autogain at the end of the transfer of a frame, at this
27  moment a frame with the old settings is being captured and transmitted. So
28  if we adjust the gain or exposure we must ignore atleast the next frame for
29  the new settings to come into effect before doing any other adjustments. */
30 #define PAC_AUTOGAIN_IGNORE_FRAMES 2
31 
32 static const unsigned char pac_sof_marker[5] =
33  { 0xff, 0xff, 0x00, 0xff, 0x96 };
34 
35 /*
36  The following state machine finds the SOF marker sequence
37  0xff, 0xff, 0x00, 0xff, 0x96 in a byte stream.
38 
39  +----------+
40  | 0: START |<---------------\
41  +----------+<-\ |
42  | \---/otherwise |
43  v 0xff |
44  +----------+ otherwise |
45  | 1 |--------------->*
46  | | ^
47  +----------+ |
48  | |
49  v 0xff |
50  +----------+<-\0xff |
51  /->| |--/ |
52  | | 2 |--------------->*
53  | | | otherwise ^
54  | +----------+ |
55  | | |
56  | v 0x00 |
57  | +----------+ |
58  | | 3 | |
59  | | |--------------->*
60  | +----------+ otherwise ^
61  | | |
62  0xff | v 0xff |
63  | +----------+ |
64  \--| 4 | |
65  | |----------------/
66  +----------+ otherwise
67  |
68  v 0x96
69  +----------+
70  | FOUND |
71  +----------+
72 */
73 
74 static unsigned char *pac_find_sof(u8 *sof_read,
75  unsigned char *m, int len)
76 {
77  int i;
78 
79  /* Search for the SOF marker (fixed part) in the header */
80  for (i = 0; i < len; i++) {
81  switch (*sof_read) {
82  case 0:
83  if (m[i] == 0xff)
84  *sof_read = 1;
85  break;
86  case 1:
87  if (m[i] == 0xff)
88  *sof_read = 2;
89  else
90  *sof_read = 0;
91  break;
92  case 2:
93  switch (m[i]) {
94  case 0x00:
95  *sof_read = 3;
96  break;
97  case 0xff:
98  /* stay in this state */
99  break;
100  default:
101  *sof_read = 0;
102  }
103  break;
104  case 3:
105  if (m[i] == 0xff)
106  *sof_read = 4;
107  else
108  *sof_read = 0;
109  break;
110  case 4:
111  switch (m[i]) {
112  case 0x96:
113  /* Pattern found */
114  PDEBUG(D_FRAM,
115  "SOF found, bytes to analyze: %u."
116  " Frame starts at byte #%u",
117  len, i + 1);
118  *sof_read = 0;
119  return m + i + 1;
120  break;
121  case 0xff:
122  *sof_read = 2;
123  break;
124  default:
125  *sof_read = 0;
126  }
127  break;
128  default:
129  *sof_read = 0;
130  }
131  }
132 
133  return NULL;
134 }
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