/drivers/media/video/gspca/pac_common.h

  1/*
  2 * Pixart PAC207BCA / PAC73xx common functions
  3 *
  4 * Copyright (C) 2008 Hans de Goede <j.w.r.degoede@hhs.nl>
  5 * Copyright (C) 2005 Thomas Kaiser thomas@kaiser-linux.li
  6 * Copyleft (C) 2005 Michel Xhaard mxhaard@magic.fr
  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
 32static 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
 74static 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}