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diff --git a/Documentation/usb/et61x251.txt b/Documentation/usb/et61x251.txt new file mode 100644 index 000000000000..b44dda407ce2 --- /dev/null +++ b/Documentation/usb/et61x251.txt @@ -0,0 +1,306 @@ + + 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'. |