+Note that the SN9C10x always returns 0 when some of its registers are read.
+To avoid race conditions, all the I/O accesses to the above files are
+serialized.
+
+The sysfs interface also provides the "frame_header" entry, which exports the
+frame header of the most recent requested and captured video frame. The header
+is 12-bytes long and is appended to every video frame by the SN9C10x
+controllers. As an example, this additional information can be used by the user
+application for implementing auto-exposure features via software.
+
+The following table describes the frame header:
+
+Byte # Value Description
+------ ----- -----------
+0x00 0xFF Frame synchronisation pattern.
+0x01 0xFF Frame synchronisation pattern.
+0x02 0x00 Frame synchronisation pattern.
+0x03 0xC4 Frame synchronisation pattern.
+0x04 0xC4 Frame synchronisation pattern.
+0x05 0x96 Frame synchronisation pattern.
+0x06 0x00 or 0x01 Unknown meaning. The exact value depends on the chip.
+0x07 0xXX Variable value, whose bits are ff00uzzc, where ff is a
+ frame counter, u is unknown, zz is a size indicator
+ (00 = VGA, 01 = SIF, 10 = QSIF) and c stands for
+ "compression enabled" (1 = yes, 0 = no).
+0x08 0xXX Brightness sum inside Auto-Exposure area (low-byte).
+0x09 0xXX Brightness sum inside Auto-Exposure area (high-byte).
+ For a pure white image, this number will be equal to 500
+ times the area of the specified AE area. For images
+ that are not pure white, the value scales down according
+ to relative whiteness.
+0x0A 0xXX Brightness sum outside Auto-Exposure area (low-byte).
+0x0B 0xXX Brightness sum outside Auto-Exposure area (high-byte).
+ For a pure white image, this number will be equal to 125
+ times the area outside of the specified AE area. For
+ images that are not pure white, the value scales down
+ according to relative whiteness.
+
+The AE area (sx, sy, ex, ey) in the active window can be set by programming the
+registers 0x1c, 0x1d, 0x1e and 0x1f of the SN9C10x controllers, where one unit
+corresponds to 32 pixels.
+
+[1] The frame header has been documented by Bertrik Sikken.
+
+
+9. Supported devices