diff options
Diffstat (limited to 'drivers/media/usb/gspca/pac_common.h')
| -rw-r--r-- | drivers/media/usb/gspca/pac_common.h | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/drivers/media/usb/gspca/pac_common.h b/drivers/media/usb/gspca/pac_common.h new file mode 100644 index 000000000..acd1be936 --- /dev/null +++ b/drivers/media/usb/gspca/pac_common.h @@ -0,0 +1,119 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * Pixart PAC207BCA / PAC73xx common functions + * + * Copyright (C) 2008 Hans de Goede <j.w.r.degoede@hhs.nl> + * Copyright (C) 2005 Thomas Kaiser thomas@kaiser-linux.li + * Copyleft (C) 2005 Michel Xhaard mxhaard@magic.fr + * + * V4L2 by Jean-Francois Moine <http://moinejf.free.fr> + */ + +/* We calculate the autogain at the end of the transfer of a frame, at this + moment a frame with the old settings is being captured and transmitted. So + if we adjust the gain or exposure we must ignore at least the next frame for + the new settings to come into effect before doing any other adjustments. */ +#define PAC_AUTOGAIN_IGNORE_FRAMES 2 + +static const unsigned char pac_sof_marker[5] = + { 0xff, 0xff, 0x00, 0xff, 0x96 }; + +/* + The following state machine finds the SOF marker sequence + 0xff, 0xff, 0x00, 0xff, 0x96 in a byte stream. + + +----------+ + | 0: START |<---------------\ + +----------+<-\ | + | \---/otherwise | + v 0xff | + +----------+ otherwise | + | 1 |--------------->* + | | ^ + +----------+ | + | | + v 0xff | + +----------+<-\0xff | + /->| |--/ | + | | 2 |--------------->* + | | | otherwise ^ + | +----------+ | + | | | + | v 0x00 | + | +----------+ | + | | 3 | | + | | |--------------->* + | +----------+ otherwise ^ + | | | + 0xff | v 0xff | + | +----------+ | + \--| 4 | | + | |----------------/ + +----------+ otherwise + | + v 0x96 + +----------+ + | FOUND | + +----------+ +*/ + +static unsigned char *pac_find_sof(struct gspca_dev *gspca_dev, u8 *sof_read, + unsigned char *m, int len) +{ + int i; + + /* Search for the SOF marker (fixed part) in the header */ + for (i = 0; i < len; i++) { + switch (*sof_read) { + case 0: + if (m[i] == 0xff) + *sof_read = 1; + break; + case 1: + if (m[i] == 0xff) + *sof_read = 2; + else + *sof_read = 0; + break; + case 2: + switch (m[i]) { + case 0x00: + *sof_read = 3; + break; + case 0xff: + /* stay in this state */ + break; + default: + *sof_read = 0; + } + break; + case 3: + if (m[i] == 0xff) + *sof_read = 4; + else + *sof_read = 0; + break; + case 4: + switch (m[i]) { + case 0x96: + /* Pattern found */ + gspca_dbg(gspca_dev, D_FRAM, + "SOF found, bytes to analyze: %u - Frame starts at byte #%u\n", + len, i + 1); + *sof_read = 0; + return m + i + 1; + break; + case 0xff: + *sof_read = 2; + break; + default: + *sof_read = 0; + } + break; + default: + *sof_read = 0; + } + } + + return NULL; +} |