path: root/Documentation/usb/zc0301.txt

                    ZC0301 Image Processor and Control Chip
                                Driver for Linux
                    =======================================

                               - Documentation -


Index
=====
1.  Copyright
2.  Disclaimer
3.  License
4.  Overview and features
5.  Module dependencies
6.  Module loading
7.  Module parameters
8.  Supported devices
9.  Notes for V4L2 application developers
10. Contact information
11. Credits


1. Copyright
============
Copyright (C) 2006 by Luca Risolia <luca.risolia@studio.unibo.it>


2. Disclaimer
=============
This software is not developed or sponsored by Z-Star Microelectronics Corp.
Trademarks are property of their respective owner.


3. License
==========
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.


4. Overview and features
========================
This driver supports the video interface of the devices mounting the ZC0301
Image Processor and Control Chip.

The driver relies on the Video4Linux2 and USB core modules. It has been
designed to run properly on SMP systems as well.

The latest version of the ZC0301 driver can be found at the following URL:
http://www.linux-projects.org/

Some of the features of the driver are:

- full compliance with the Video4Linux2 API (see also "Notes for V4L2
  application developers" paragraph);
- available mmap or read/poll methods for video streaming through isochronous
  data transfers;
- automatic detection of image sensor;
- video formats is standard JPEG in various compression qualities
  (see also "Notes for V4L2 application developers" paragraph);
- full support for the capabilities of every possible image sensors that can
  be connected to the ZC0301 bridges, including, for istance, red, green,
  blue and global gain adjustments and exposure control (see "Supported
  devices" paragraph for details);
- use of default color settings for sunlight conditions;
- dynamic driver control thanks to various module parameters (see "Module
  parameters" paragraph);
- up to 64 cameras can be handled at the same time; they can be connected and
  disconnected from the host many times without turning off the computer, if
  the system supports hotplugging;


5. Module dependencies
======================
For it to work properly, the driver needs kernel support for Video4Linux and
USB.

The following options of the kernel configuration file must be enabled and
corresponding modules must be compiled:

	# Multimedia devices
	#
	CONFIG_VIDEO_DEV=m

	# USB support
	#
	CONFIG_USB=m

In addition, depending on the hardware being used, the modules below are
necessary:

	# USB Host Controller Drivers
	#
	CONFIG_USB_EHCI_HCD=m
	CONFIG_USB_UHCI_HCD=m
	CONFIG_USB_OHCI_HCD=m

The ZC0301 controller also provides a built-in microphone interface. It is
supported by the USB Audio driver thanks to the ALSA API:

	# Sound
	#
	CONFIG_SOUND=y

	# Advanced Linux Sound Architecture
	#
	CONFIG_SND=m

	# USB devices
	#
	CONFIG_SND_USB_AUDIO=m

And finally:

	# USB Multimedia devices
	#
	CONFIG_USB_ZC0301=m


6. Module loading
=================
To use the driver, it is necessary to load the "zc0301" module into memory
after every other module required: "videodev", "usbcore" and, depending on
the USB host controller you have, "ehci-hcd", "uhci-hcd" or "ohci-hcd".

Loading can be done as shown below:

	[root@localhost home]# modprobe zc0301

At this point the devices should be recognized. You can invoke "dmesg" to
analyze kernel messages and verify that the loading process has gone well:

	[user@localhost home]$ dmesg


7. Module parameters
====================
Module parameters are listed below:
-------------------------------------------------------------------------------
Name:           video_nr
Type:           short array (min = 0, max = 64)
Syntax:         <-1|n[,...]>
Description:    Specify V4L2 minor mode number:
                -1 = use next available
                 n = use minor number n
                You can specify up to 64 cameras this way.
                For example:
                video_nr=-1,2,-1 would assign minor number 2 to the second
                registered camera and use auto for the first one and for every
                other camera.
Default:        -1
-------------------------------------------------------------------------------
Name:           force_munmap
Type:           bool array (min = 0, max = 64)
Syntax:         <0|1[,...]>
Description:    Force the application to unmap previously mapped buffer memory
                before calling any VIDIOC_S_CROP or VIDIOC_S_FMT ioctl's. Not
                all the applications support this feature. This parameter is
                specific for each detected camera.
                0 = do not force memory unmapping
                1 = force memory unmapping (save memory)
Default:        0
-------------------------------------------------------------------------------
Name:           debug
Type:           ushort
Syntax:         <n>
Description:    Debugging information level, from 0 to 3:
                0 = none (use carefully)
                1 = critical errors
                2 = significant informations
                3 = more verbose messages
                Level 3 is useful for testing only, when only one device
                is used at the same time. It also shows some more informations
                about the hardware being detected. This module parameter can be
                changed at runtime thanks to the /sys filesystem interface.
Default:        2
-------------------------------------------------------------------------------


8. Supported devices
====================
None of the names of the companies as well as their products will be mentioned
here. They have never collaborated with the author, so no advertising.

From the point of view of a driver, what unambiguously identify a device are
its vendor and product USB identifiers. Below is a list of known identifiers of
devices mounting the ZC0301 Image Processor and Control Chips:

Vendor ID  Product ID
---------  ----------
0x046d     0x08ae

The following image sensors are supported:

Model       Manufacturer
-----       ------------
PAS202BCB   PixArt Imaging, Inc.

All the available control settings of each image sensor are supported through
the V4L2 interface.


9. Notes for V4L2 application developers
========================================
This driver follows the V4L2 API specifications. In particular, it enforces two
rules:

- exactly one I/O method, either "mmap" or "read", is associated with each
file descriptor. Once it is selected, the application must close and reopen the
device to switch to the other I/O method;

- although it is not mandatory, previously mapped buffer memory should always
be unmapped before calling any "VIDIOC_S_CROP" or "VIDIOC_S_FMT" ioctl's.
The same number of buffers as before will be allocated again to match the size
of the new video frames, so you have to map the buffers again before any I/O
attempts on them.

This driver supports the standard JPEG video format. The current compression
quality may vary from 0 to 3 and can be selected or queried thanks to the
VIDIOC_S_JPEGCOMP and VIDIOC_G_JPEGCOMP V4L2 ioctl's.


10. Contact information
=======================
The author may be contacted by e-mail at <luca.risolia@studio.unibo.it>.

GPG/PGP encrypted e-mail's are accepted. The GPG key ID of the author is
'FCE635A4'; the public 1024-bit key should be available at any keyserver;
the fingerprint is: '88E8 F32F 7244 68BA 3958  5D40 99DA 5D2A FCE6 35A4'.


11. Credits
===========
- Informations about the chip internals to enable the I2C protocol have been
  taken from the documentation of the ZC030x Video4Linux1 driver written by
  Andrew Birkett <andy@nobugs.org>;
- Initialization values of the ZC0301 connected to the PAS202BCB image sensor
  have been taken from the SPCA5XX driver maintained by
  Michel Xhaard  <mxhaard@magic.fr>