sn9c102.txt

Linux Kernel 2.6.9 for OMAP1710

                        SN9C10[12] PC Camera Controllers
                                Driver for Linux
                        ================================

                               - Documentation -


Index
=====
1.  Copyright
2.  License
3.  Overview
4.  Module dependencies
5.  Module loading
6.  Module parameters
7.  Optional device control through "sysfs"
8.  Supported devices
9.  How to add support for new image sensors
10. Notes for V4L2 application developers
11. Contact information
12. Credits


1. Copyright
============
Copyright (C) 2004 by Luca Risolia <[e-mail]>

SONiX is a trademark of SONiX Technology Company Limited, inc.
This driver is not sponsored or developed by SONiX.


2. 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.


3. Overview
===========
This driver attempts to support the video streaming capabilities of the devices
mounting the SONiX SN9C101 or SONiX SN9C102 PC Camera Controllers.

- It's worth to note that SONiX has never collaborated with me during the
development of this project, despite of several requests for enough detailed
specifications of the register tables, compression engine and video data format
of the above chips -

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
your system supports the hotplug facility.

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 SN9C10[12] driver can be found at the following URL:
http://go.lamarinapunto.com/


4. 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

And finally:

	# USB Multimedia devices
	#
	CONFIG_USB_SN9C102=m


5. Module loading
=================
To use the driver, it is necessary to load the "sn9c102" 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 usbcore
	[root@localhost home]# modprobe sn9c102

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


6. Module parameters
====================
Module parameters are listed below:
-------------------------------------------------------------------------------
Name:           video_nr
Type:           int array (min = 0, max = 32)
Syntax:         <-1|n[,...]> 
Description:    Specify V4L2 minor mode number:
                -1 = use next available
                 n = use minor number n
                You can specify up to 32 cameras this way.
                For example:
                video_nr=-1,2,-1 would assign minor number 2 to the second
                recognized camera and use auto for the first one and for every
                other camera.
Default:        -1
-------------------------------------------------------------------------------
Name:           debug
Type:           int
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.
Default:        2
-------------------------------------------------------------------------------


7. Optional device control through "sysfs"
==========================================
It is possible to read and write both the SN9C10[12] and the image sensor
registers by using the "sysfs" filesystem interface.

Every time a supported device is recognized, a read-only file named "green" is
created in the /sys/class/video4linux/videoX directory. You can set the green
channel's gain by writing the desired value to it. The value may range from 0
to 15.

There are other four entries in the directory above for each registered camera:
"reg", "val", "i2c_reg" and "i2c_val". The first two files control the
SN9C10[12] bridge, while the other two control the sensor chip. "reg" and
"i2c_reg" hold the values of the current register index where the following
reading/writing operations are addressed at through "val" and "i2c_val". Their
use is not intended for end-users, unless you know what you are doing. Note
that "i2c_reg" and "i2c_val" won't be created if the sensor does not actually
support the standard I2C protocol. Also, remember that you must be logged in as
root before writing to them.

As an example, suppose we were to want to read the value contained in the
register number 1 of the sensor register table - which usually is the product
identifier - of the camera registered as "/dev/video0":

	[root@localhost #] cd /sys/class/video4linux/video0
	[root@localhost #] echo 1 > i2c_reg
	[root@localhost #] cat i2c_val

Now let's set the green gain's register of the SN9C10[12] chip to 2:

	[root@localhost #] echo 0x11 > reg
	[root@localhost #] echo 2 > val

Note that the SN9C10[12] always returns 0 when some of its registers are read.
To avoid race conditions, all the I/O accesses to the files are serialized.


8. Supported devices
====================
- I won't mention any of the names of the companies as well as their products
here. They have never collaborated with me, 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 SN9C10[12] PC camera controllers:

Vendor ID  Product ID
---------  ----------
0xc45      0x6001
0xc45      0x6005
0xc45      0x6009
0xc45      0x600d
0xc45      0x6024
0xc45      0x6025
0xc45      0x6028
0xc45      0x6029
0xc45      0x602a
0xc45      0x602c
0xc45      0x6030

The list above does NOT imply that all those devices work with this driver: up
until now only the ones that mount the following image sensors are supported.
Kernel messages will always tell you whether this is the case:

Model       Manufacturer
-----       ------------
PAS106B     PixArt Imaging Inc.
PAS202BCB   PixArt Imaging Inc.
TAS5110C1B  Taiwan Advanced Sensor Corporation
TAS5130D1B  Taiwan Advanced Sensor Corporation

If you think your camera is based on the above hardware and is not actually
listed in the above table, you may try to add the specific USB VendorID and
ProductID identifiers to the sn9c102_id_table[] in the file "sn9c102_sensor.h";
then compile, load the module again and look at the kernel output.
If this works, please send an email to me reporting the kernel messages, so
that I will add a new entry in the list of supported devices.

Donations of new models for further testing and support would be much
appreciated. I won't add official support for hardware that I don't actually
have.


9. How to add support for new image sensors
===========================================
It should be easy to write code for new sensors by using the small API that I
have created for this purpose, which is present in "sn9c102_sensor.h"
(documentation is included there). As an example, have a look at the code in
"sn9c102_pas106b.c", which uses the mentioned interface.

At the moment, not yet supported image sensors are: HV7131[D|E1] (VGA),
MI03 (VGA), OV7620 (VGA).


10. 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;

- previously mapped buffer memory must always be unmapped before calling any
of the "VIDIOC_S_CROP", "VIDIOC_TRY_FMT" and "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 them again before any I/O attempts.

Consistently with the hardware limits, this driver also supports image
downscaling with arbitrary scaling factors from 1, 2 and 4 in both directions.
However the V4L2 API specifications don't correctly define how the scaling
factor can be choosen arbitrarily by the "negotiation" of the "source" and
"target" rectangles. To work around this flaw, we have added the convention
that, during the negotiation, whenever the "VIDIOC_S_CROP" ioctl is issued, the
scaling factor is restored to 1.


11. Contact information
=======================
I may be contacted by e-mail at <[e-mail]>.

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


12. Credits
===========
I would thank the following persons:

- Stefano Mozzi, who donated 45 EU;
- Luca Capello for the donation of a webcam;
- Mizuno Takafumi for the donation of a webcam;
- Carlos Eduardo Medaglia Dyonisio, who added the support for the PAS202BCB
  image sensor.