mirror of https://gitee.com/openkylin/linux.git
307 lines
11 KiB
Plaintext
307 lines
11 KiB
Plaintext
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ET61X[12]51 PC Camera Controllers
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Driver for Linux
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=================================
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- Documentation -
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Index
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=====
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1. Copyright
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2. Disclaimer
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3. License
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4. Overview and features
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5. Module dependencies
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6. Module loading
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7. Module parameters
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8. Optional device control through "sysfs"
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9. Supported devices
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10. Notes for V4L2 application developers
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11. Contact information
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1. Copyright
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============
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Copyright (C) 2006 by Luca Risolia <luca.risolia@studio.unibo.it>
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2. Disclaimer
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=============
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Etoms is a trademark of Etoms Electronics Corp.
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This software is not developed or sponsored by Etoms Electronics.
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3. License
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==========
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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4. Overview and features
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========================
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This driver supports the video interface of the devices mounting the ET61X151
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or ET61X251 PC Camera Controllers.
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It's worth to note that Etoms Electronics has never collaborated with the
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author during the development of this project; despite several requests,
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Etoms Electronics also refused to release enough detailed specifications of
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the video compression engine.
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The driver relies on the Video4Linux2 and USB core modules. It has been
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designed to run properly on SMP systems as well.
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The latest version of the ET61X[12]51 driver can be found at the following URL:
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http://www.linux-projects.org/
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Some of the features of the driver are:
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- full compliance with the Video4Linux2 API (see also "Notes for V4L2
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application developers" paragraph);
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- available mmap or read/poll methods for video streaming through isochronous
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data transfers;
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- automatic detection of image sensor;
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- support for any window resolutions and optional panning within the maximum
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pixel area of image sensor;
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- image downscaling with arbitrary scaling factors from 1 and 2 in both
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directions (see "Notes for V4L2 application developers" paragraph);
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- two different video formats for uncompressed or compressed data in low or
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high compression quality (see also "Notes for V4L2 application developers"
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paragraph);
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- full support for the capabilities of every possible image sensors that can
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be connected to the ET61X[12]51 bridges, including, for istance, red, green,
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blue and global gain adjustments and exposure control (see "Supported
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devices" paragraph for details);
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- use of default color settings for sunlight conditions;
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- dynamic I/O interface for both ET61X[12]51 and image sensor control (see
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"Optional device control through 'sysfs'" paragraph);
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- dynamic driver control thanks to various module parameters (see "Module
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parameters" paragraph);
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- up to 64 cameras can be handled at the same time; they can be connected and
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disconnected from the host many times without turning off the computer, if
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the system supports hotplugging;
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- no known bugs.
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5. Module dependencies
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======================
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For it to work properly, the driver needs kernel support for Video4Linux and
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USB.
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The following options of the kernel configuration file must be enabled and
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corresponding modules must be compiled:
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# Multimedia devices
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#
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CONFIG_VIDEO_DEV=m
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To enable advanced debugging functionality on the device through /sysfs:
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# Multimedia devices
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#
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CONFIG_VIDEO_ADV_DEBUG=y
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# USB support
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#
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CONFIG_USB=m
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In addition, depending on the hardware being used, the modules below are
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necessary:
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# USB Host Controller Drivers
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#
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CONFIG_USB_EHCI_HCD=m
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CONFIG_USB_UHCI_HCD=m
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CONFIG_USB_OHCI_HCD=m
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And finally:
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# USB Multimedia devices
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#
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CONFIG_USB_ET61X251=m
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6. Module loading
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=================
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To use the driver, it is necessary to load the "et61x251" module into memory
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after every other module required: "videodev", "usbcore" and, depending on
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the USB host controller you have, "ehci-hcd", "uhci-hcd" or "ohci-hcd".
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Loading can be done as shown below:
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[root@localhost home]# modprobe et61x251
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At this point the devices should be recognized. You can invoke "dmesg" to
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analyze kernel messages and verify that the loading process has gone well:
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[user@localhost home]$ dmesg
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7. Module parameters
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====================
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Module parameters are listed below:
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-------------------------------------------------------------------------------
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Name: video_nr
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Type: short array (min = 0, max = 64)
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Syntax: <-1|n[,...]>
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Description: Specify V4L2 minor mode number:
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-1 = use next available
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n = use minor number n
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You can specify up to 64 cameras this way.
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For example:
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video_nr=-1,2,-1 would assign minor number 2 to the second
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registered camera and use auto for the first one and for every
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other camera.
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Default: -1
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-------------------------------------------------------------------------------
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Name: force_munmap
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Type: bool array (min = 0, max = 64)
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Syntax: <0|1[,...]>
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Description: Force the application to unmap previously mapped buffer memory
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before calling any VIDIOC_S_CROP or VIDIOC_S_FMT ioctl's. Not
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all the applications support this feature. This parameter is
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specific for each detected camera.
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0 = do not force memory unmapping
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1 = force memory unmapping (save memory)
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Default: 0
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-------------------------------------------------------------------------------
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Name: debug
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Type: ushort
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Syntax: <n>
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Description: Debugging information level, from 0 to 3:
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0 = none (use carefully)
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1 = critical errors
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2 = significant informations
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3 = more verbose messages
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Level 3 is useful for testing only, when only one device
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is used at the same time. It also shows some more informations
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about the hardware being detected. This module parameter can be
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changed at runtime thanks to the /sys filesystem interface.
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Default: 2
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-------------------------------------------------------------------------------
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8. Optional device control through "sysfs"
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==========================================
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If the kernel has been compiled with the CONFIG_VIDEO_ADV_DEBUG option enabled,
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it is possible to read and write both the ET61X[12]51 and the image sensor
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registers by using the "sysfs" filesystem interface.
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There are four files in the /sys/class/video4linux/videoX directory for each
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registered camera: "reg", "val", "i2c_reg" and "i2c_val". The first two files
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control the ET61X[12]51 bridge, while the other two control the sensor chip.
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"reg" and "i2c_reg" hold the values of the current register index where the
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following reading/writing operations are addressed at through "val" and
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"i2c_val". Their use is not intended for end-users, unless you know what you
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are doing. Remember that you must be logged in as root before writing to them.
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As an example, suppose we were to want to read the value contained in the
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register number 1 of the sensor register table - which is usually the product
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identifier - of the camera registered as "/dev/video0":
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[root@localhost #] cd /sys/class/video4linux/video0
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[root@localhost #] echo 1 > i2c_reg
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[root@localhost #] cat i2c_val
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Note that if the sensor registers can not be read, "cat" will fail.
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To avoid race conditions, all the I/O accesses to the files are serialized.
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9. Supported devices
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====================
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None of the names of the companies as well as their products will be mentioned
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here. They have never collaborated with the author, so no advertising.
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From the point of view of a driver, what unambiguously identify a device are
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its vendor and product USB identifiers. Below is a list of known identifiers of
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devices mounting the ET61X[12]51 PC camera controllers:
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Vendor ID Product ID
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--------- ----------
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0x102c 0x6151
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0x102c 0x6251
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0x102c 0x6253
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0x102c 0x6254
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0x102c 0x6255
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0x102c 0x6256
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0x102c 0x6257
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0x102c 0x6258
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0x102c 0x6259
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0x102c 0x625a
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0x102c 0x625b
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0x102c 0x625c
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0x102c 0x625d
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0x102c 0x625e
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0x102c 0x625f
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0x102c 0x6260
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0x102c 0x6261
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0x102c 0x6262
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0x102c 0x6263
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0x102c 0x6264
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0x102c 0x6265
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0x102c 0x6266
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0x102c 0x6267
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0x102c 0x6268
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0x102c 0x6269
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The following image sensors are supported:
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Model Manufacturer
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----- ------------
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TAS5130D1B Taiwan Advanced Sensor Corporation
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All the available control settings of each image sensor are supported through
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the V4L2 interface.
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10. Notes for V4L2 application developers
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========================================
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This driver follows the V4L2 API specifications. In particular, it enforces two
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rules:
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- exactly one I/O method, either "mmap" or "read", is associated with each
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file descriptor. Once it is selected, the application must close and reopen the
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device to switch to the other I/O method;
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- although it is not mandatory, previously mapped buffer memory should always
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be unmapped before calling any "VIDIOC_S_CROP" or "VIDIOC_S_FMT" ioctl's.
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The same number of buffers as before will be allocated again to match the size
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of the new video frames, so you have to map the buffers again before any I/O
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attempts on them.
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Consistently with the hardware limits, this driver also supports image
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downscaling with arbitrary scaling factors from 1 and 2 in both directions.
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However, the V4L2 API specifications don't correctly define how the scaling
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factor can be chosen arbitrarily by the "negotiation" of the "source" and
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"target" rectangles. To work around this flaw, we have added the convention
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that, during the negotiation, whenever the "VIDIOC_S_CROP" ioctl is issued, the
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scaling factor is restored to 1.
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This driver supports two different video formats: the first one is the "8-bit
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Sequential Bayer" format and can be used to obtain uncompressed video data
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from the device through the current I/O method, while the second one provides
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"raw" compressed video data (without frame headers not related to the
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compressed data). The current compression quality may vary from 0 to 1 and can
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be selected or queried thanks to the VIDIOC_S_JPEGCOMP and VIDIOC_G_JPEGCOMP
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V4L2 ioctl's.
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11. Contact information
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=======================
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The author may be contacted by e-mail at <luca.risolia@studio.unibo.it>.
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GPG/PGP encrypted e-mail's are accepted. The GPG key ID of the author is
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'FCE635A4'; the public 1024-bit key should be available at any keyserver;
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the fingerprint is: '88E8 F32F 7244 68BA 3958 5D40 99DA 5D2A FCE6 35A4'.
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