1.. SPDX-License-Identifier: GPL-2.0
2
3The cpia2 driver
4================
5
6Authors: Peter Pregler <Peter_Pregler@email.com>,
7Scott J. Bertin <scottbertin@yahoo.com>, and
8Jarl Totland <Jarl.Totland@bdc.no> for the original cpia driver, which
9this one was modelled from.
10
11
12Notes to developers
13~~~~~~~~~~~~~~~~~~~
14
15   - This is a driver version stripped of the 2.4 back compatibility
16     and old MJPEG ioctl API. See cpia2.sf.net for 2.4 support.
17
18Programmer's overview of cpia2 driver
19~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
20
21Cpia2 is the second generation video coprocessor from VLSI Vision Ltd (now a
22division of ST Microelectronics).  There are two versions.  The first is the
23STV0672, which is capable of up to 30 frames per second (fps) in frame sizes
24up to CIF, and 15 fps for VGA frames.  The STV0676 is an improved version,
25which can handle up to 30 fps VGA.  Both coprocessors can be attached to two
26CMOS sensors - the vvl6410 CIF sensor and the vvl6500 VGA sensor.  These will
27be referred to as the 410 and the 500 sensors, or the CIF and VGA sensors.
28
29The two chipsets operate almost identically.  The core is an 8051 processor,
30running two different versions of firmware.  The 672 runs the VP4 video
31processor code, the 676 runs VP5.  There are a few differences in register
32mappings for the two chips.  In these cases, the symbols defined in the
33header files are marked with VP4 or VP5 as part of the symbol name.
34
35The cameras appear externally as three sets of registers. Setting register
36values is the only way to control the camera.  Some settings are
37interdependant, such as the sequence required to power up the camera. I will
38try to make note of all of these cases.
39
40The register sets are called blocks.  Block 0 is the system block.  This
41section is always powered on when the camera is plugged in.  It contains
42registers that control housekeeping functions such as powering up the video
43processor.  The video processor is the VP block.  These registers control
44how the video from the sensor is processed.  Examples are timing registers,
45user mode (vga, qvga), scaling, cropping, framerates, and so on.  The last
46block is the video compressor (VC).  The video stream sent from the camera is
47compressed as Motion JPEG (JPEGA).  The VC controls all of the compression
48parameters.  Looking at the file cpia2_registers.h, you can get a full view
49of these registers and the possible values for most of them.
50
51One or more registers can be set or read by sending a usb control message to
52the camera.  There are three modes for this.  Block mode requests a number
53of contiguous registers.  Random mode reads or writes random registers with
54a tuple structure containing address/value pairs.  The repeat mode is only
55used by VP4 to load a firmware patch.  It contains a starting address and
56a sequence of bytes to be written into a gpio port.
57