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+
+                         SN9C10x PC Camera Controllers
+                                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.  Optional device control through "sysfs"
+9.  Supported devices
+10. How to add plug-in's for new image sensors
+11. Notes for V4L2 application developers
+12. Video frame formats
+13. Contact information
+14. Credits
+
+
+1. Copyright
+============
+Copyright (C) 2004-2005 by Luca Risolia <luca.risolia@studio.unibo.it>
+
+
+2. Disclaimer
+=============
+SONiX is a trademark of SONiX Technology Company Limited, inc.
+This software is not sponsored or developed by SONiX.
+
+
+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 attempts to support the video and audio streaming capabilities of
+the devices mounting the SONiX SN9C101, SN9C102 and SN9C103 PC Camera
+Controllers.
+
+It's worth to note that SONiX has never collaborated with the author during the
+development of this project, despite several requests for enough detailed
+specifications of the register tables, compression engine and video data format
+of the above chips. Nevertheless, these informations are no longer necessary,
+becouse all the aspects related to these chips are known and have been
+described in detail in this documentation.
+
+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 SN9C10x 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;
+- support for any window resolutions and optional panning within the maximum
+  pixel area of image sensor;
+- image downscaling with arbitrary scaling factors from 1, 2 and 4 in both
+  directions (see "Notes for V4L2 application developers" paragraph);
+- two different video formats for uncompressed or compressed data in low or
+  high compression quality (see also "Notes for V4L2 application developers"
+  and "Video frame formats" paragraphs);
+- full support for the capabilities of many of the possible image sensors that
+  can be connected to the SN9C10x bridges, including, for istance, red, green,
+  blue and global gain adjustments and exposure (see "Supported devices"
+  paragraph for details);
+- use of default color settings for sunlight conditions;
+- dynamic I/O interface for both SN9C10x and image sensor control and
+  monitoring (see "Optional device control through 'sysfs'" paragraph);
+- 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
+  your system supports hotplugging;
+- no known bugs.
+
+
+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
+
+And finally:
+
+        # USB Multimedia devices
+        #
+        CONFIG_USB_SN9C102=m
+
+
+6. 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 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
+
+
+7. Module parameters
+====================
+Module parameters are listed below:
+-------------------------------------------------------------------------------
+Name:           video_nr
+Type:           int 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
+                recognized 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:           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. It also shows some more informations about the
+                hardware being detected. This parameter can be changed at
+                runtime thanks to the /sys filesystem.
+Default:        2
+-------------------------------------------------------------------------------
+
+
+8. Optional device control through "sysfs" [1]
+==========================================
+It is possible to read and write both the SN9C10x and the image sensor
+registers by using the "sysfs" filesystem interface.
+
+Every time a supported device is recognized, a write-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 for SN9C101 or SN9C102 bridges, from 0 to 127 for SN9C103 bridges.
+Similarly, only for SN9C103 controllers, blue and red gain control files are
+available in the same directory, for which accepted values may range from 0 to
+127.
+
+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
+SN9C10x 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. Note that "i2c_reg" and "i2c_val" will not
+be created if the sensor does not actually support the standard I2C protocol or
+its registers are not 8-bit long. 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 is usually 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
+
+Note that "cat" will fail if sensor registers cannot be read.
+
+Now let's set the green gain's register of the SN9C101 or SN9C102 chips to 2:
+
+        [root@localhost #] echo 0x11 > reg
+        [root@localhost #] echo 2 > val
+
+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
+====================
+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 SN9C10x PC camera controllers:
+
+Vendor ID  Product ID
+---------  ----------
+0x0c45     0x6001
+0x0c45     0x6005
+0x0c45     0x6009
+0x0c45     0x600d
+0x0c45     0x6024
+0x0c45     0x6025
+0x0c45     0x6028
+0x0c45     0x6029
+0x0c45     0x602a
+0x0c45     0x602b
+0x0c45     0x602c
+0x0c45     0x6030
+0x0c45     0x6080
+0x0c45     0x6082
+0x0c45     0x6083
+0x0c45     0x6088
+0x0c45     0x608a
+0x0c45     0x608b
+0x0c45     0x608c
+0x0c45     0x608e
+0x0c45     0x608f
+0x0c45     0x60a0
+0x0c45     0x60a2
+0x0c45     0x60a3
+0x0c45     0x60a8
+0x0c45     0x60aa
+0x0c45     0x60ab
+0x0c45     0x60ac
+0x0c45     0x60ae
+0x0c45     0x60af
+0x0c45     0x60b0
+0x0c45     0x60b2
+0x0c45     0x60b3
+0x0c45     0x60b8
+0x0c45     0x60ba
+0x0c45     0x60bb
+0x0c45     0x60bc
+0x0c45     0x60be
+
+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
+-----       ------------
+HV7131D     Hynix Semiconductor, Inc.
+MI-0343     Micron Technology, Inc.
+PAS106B     PixArt Imaging, Inc.
+PAS202BCB   PixArt Imaging, Inc.
+TAS5110C1B  Taiwan Advanced Sensor Corporation
+TAS5130D1B  Taiwan Advanced Sensor Corporation
+
+All the available control settings of each image sensor are supported through
+the V4L2 interface.
+
+Donations of new models for further testing and support would be much
+appreciated. Non-available hardware will not be supported by the author of this
+driver.
+
+
+10. How to add plug-in's for new image sensors
+==============================================
+It should be easy to write plug-in's for new sensors by using the small API
+that has been 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, possible unsupported image sensors are: CIS-VF10 (VGA),
+OV7620 (VGA), OV7630 (VGA).
+
+
+11. 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.
+
+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 chosen 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.
+
+This driver supports two different video formats: the first one is the "8-bit
+Sequential Bayer" format and can be used to obtain uncompressed video data
+from the device through the current I/O method, while the second one provides
+"raw" compressed video data (without frame headers not related to the
+compressed data). The compression quality may vary from 0 to 1 and can be
+selected or queried thanks to the VIDIOC_S_JPEGCOMP and VIDIOC_G_JPEGCOMP V4L2
+ioctl's. For maximum flexibility, both the default active video format and the
+default compression quality depend on how the image sensor being used is
+initialized (as described in the documentation of the API for the image sensors
+supplied by this driver).
+
+
+12. Video frame formats [1]
+=======================
+The SN9C10x PC Camera Controllers can send images in two possible video
+formats over the USB: either native "Sequential RGB Bayer" or Huffman
+compressed. The latter is used to achieve high frame rates. The current video
+format may be selected or queried from the user application by calling the
+VIDIOC_S_FMT or VIDIOC_G_FMT ioctl's, as described in the V4L2 API
+specifications.
+
+The name "Sequential Bayer" indicates the organization of the red, green and
+blue pixels in one video frame. Each pixel is associated with a 8-bit long
+value and is disposed in memory according to the pattern shown below:
+
+B[0]   G[1]    B[2]    G[3]    ...   B[m-2]         G[m-1]
+G[m]   R[m+1]  G[m+2]  R[m+2]  ...   G[2m-2]        R[2m-1] 
+...
+...                                  B[(n-1)(m-2)]  G[(n-1)(m-1)]
+...                                  G[n(m-2)]      R[n(m-1)]
+
+The above matrix also represents the sequential or progressive read-out mode of
+the (n, m) Bayer color filter array used in many CCD/CMOS image sensors.
+
+One compressed video frame consists of a bitstream that encodes for every R, G,
+or B pixel the difference between the value of the pixel itself and some
+reference pixel value. Pixels are organised in the Bayer pattern and the Bayer
+sub-pixels are tracked individually and alternatingly. For example, in the
+first line values for the B and G1 pixels are alternatingly encoded, while in
+the second line values for the G2 and R pixels are alternatingly encoded.
+
+The pixel reference value is calculated as follows:
+- the 4 top left pixels are encoded in raw uncompressed 8-bit format;
+- the value in the top two rows is the value of the pixel left of the current
+  pixel;
+- the value in the left column is the value of the pixel above the current
+  pixel;
+- for all other pixels, the reference value is the average of the value of the
+  pixel on the left and the value of the pixel above the current pixel;
+- there is one code in the bitstream that specifies the value of a pixel
+  directly (in 4-bit resolution);
+- pixel values need to be clamped inside the range [0..255] for proper
+  decoding.
+
+The algorithm purely describes the conversion from compressed Bayer code used
+in the SN9C10x chips to uncompressed Bayer. Additional steps are required to
+convert this to a color image (i.e. a color interpolation algorithm).
+ 
+The following Huffman codes have been found:
+0: +0 (relative to reference pixel value) 
+100: +4
+101: -4?
+1110xxxx: set absolute value to xxxx.0000 
+1101: +11
+1111: -11
+11001: +20
+110000: -20
+110001: ??? - these codes are apparently not used
+
+[1] The Huffman compression algorithm has been reverse-engineered and
+    documented by Bertrik Sikken.
+
+
+13. 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'.
+
+
+14. Credits
+===========
+Many thanks to following persons for their contribute (listed in alphabetical
+order):
+
+- Luca Capello for the donation of a webcam;
+- Joao Rodrigo Fuzaro, Joao Limirio, Claudio Filho and Caio Begotti for the
+  donation of a webcam;
+- Carlos Eduardo Medaglia Dyonisio, who added the support for the PAS202BCB
+  image sensor;
+- Stefano Mozzi, who donated 45 EU;
+- Bertrik Sikken, who reverse-engineered and documented the Huffman compression
+  algorithm used in the SN9C10x controllers and implemented the first decoder;
+- Mizuno Takafumi for the donation of a webcam;
+- An "anonymous" donator (who didn't want his name to be revealed) for the
+  donation of a webcam.