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+
+                       ET61X[12]51 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. Notes for V4L2 application developers
+11. Contact information
+
+
+1. Copyright
+============
+Copyright (C) 2006 by Luca Risolia <luca.risolia@studio.unibo.it>
+
+
+2. Disclaimer
+=============
+Etoms is a trademark of Etoms Electronics Corp.
+This software is not developed or sponsored by Etoms Electronics.
+
+
+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 ET61X151
+or ET61X251 PC Camera Controllers.
+
+It's worth to note that Etoms Electronics has never collaborated with the
+author during the development of this project; despite several requests,
+Etoms Electronics also refused to release enough detailed specifications of
+the video compression engine.
+
+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 ET61X[12]51 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 and 2 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"
+  paragraph);
+- full support for the capabilities of every possible image sensors that can
+  be connected to the ET61X[12]51 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 I/O interface for both ET61X[12]51 and image sensor control (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
+  the 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
+
+To enable advanced debugging functionality on the device through /sysfs:
+
+	# Multimedia devices
+	#
+	CONFIG_VIDEO_ADV_DEBUG=y
+
+	# 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_ET61X251=m
+
+
+6. Module loading
+=================
+To use the driver, it is necessary to load the "et61x251" 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 et61x251
+
+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. Optional device control through "sysfs"
+==========================================
+If the kernel has been compiled with the CONFIG_VIDEO_ADV_DEBUG option enabled,
+it is possible to read and write both the ET61X[12]51 and the image sensor
+registers by using the "sysfs" filesystem interface.
+
+There are four files in the /sys/class/video4linux/videoX directory for each
+registered camera: "reg", "val", "i2c_reg" and "i2c_val". The first two files
+control the ET61X[12]51 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. 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 if the sensor registers can not be read, "cat" will fail.
+To avoid race conditions, all the I/O accesses to the files are serialized.
+
+
+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 ET61X[12]51 PC camera controllers:
+
+Vendor ID  Product ID
+---------  ----------
+0x102c     0x6151
+0x102c     0x6251
+0x102c     0x6253
+0x102c     0x6254
+0x102c     0x6255
+0x102c     0x6256
+0x102c     0x6257
+0x102c     0x6258
+0x102c     0x6259
+0x102c     0x625a
+0x102c     0x625b
+0x102c     0x625c
+0x102c     0x625d
+0x102c     0x625e
+0x102c     0x625f
+0x102c     0x6260
+0x102c     0x6261
+0x102c     0x6262
+0x102c     0x6263
+0x102c     0x6264
+0x102c     0x6265
+0x102c     0x6266
+0x102c     0x6267
+0x102c     0x6268
+0x102c     0x6269
+
+The following image sensors are supported:
+
+Model       Manufacturer
+-----       ------------
+TAS5130D1B  Taiwan Advanced Sensor Corporation
+
+All the available control settings of each image sensor are supported through
+the V4L2 interface.
+
+
+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;
+
+- 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 and 2 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 current 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.
+
+
+11. 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'.