cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

pac_common.h (2922B)

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