| blob | e0cdae49185802b11fc0795e5c99dcf47bfc3e3c |
2 ET61X[12]51 PC Camera Controllers
3 Driver for Linux
4 =================================
6 - Documentation -
9 Index
10 =====
11 1. Copyright
12 2. Disclaimer
13 3. License
14 4. Overview and features
15 5. Module dependencies
16 6. Module loading
17 7. Module parameters
18 8. Optional device control through "sysfs"
19 9. Supported devices
20 10. Notes for V4L2 application developers
21 11. Contact information
24 1. Copyright
25 ============
26 Copyright (C) 2006-2007 by Luca Risolia <luca.risolia@studio.unibo.it>
29 2. Disclaimer
30 =============
31 Etoms is a trademark of Etoms Electronics Corp.
32 This software is not developed or sponsored by Etoms Electronics.
35 3. License
36 ==========
37 This program is free software; you can redistribute it and/or modify
38 it under the terms of the GNU General Public License as published by
39 the Free Software Foundation; either version 2 of the License, or
40 (at your option) any later version.
42 This program is distributed in the hope that it will be useful,
43 but WITHOUT ANY WARRANTY; without even the implied warranty of
44 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
45 GNU General Public License for more details.
47 You should have received a copy of the GNU General Public License
48 along with this program; if not, write to the Free Software
49 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
52 4. Overview and features
53 ========================
54 This driver supports the video interface of the devices mounting the ET61X151
55 or ET61X251 PC Camera Controllers.
57 It's worth to note that Etoms Electronics has never collaborated with the
58 author during the development of this project; despite several requests,
59 Etoms Electronics also refused to release enough detailed specifications of
60 the video compression engine.
62 The driver relies on the Video4Linux2 and USB core modules. It has been
63 designed to run properly on SMP systems as well.
65 The latest version of the ET61X[12]51 driver can be found at the following URL:
66 http://www.linux-projects.org/
68 Some of the features of the driver are:
70 - full compliance with the Video4Linux2 API (see also "Notes for V4L2
71 application developers" paragraph);
72 - available mmap or read/poll methods for video streaming through isochronous
73 data transfers;
74 - automatic detection of image sensor;
75 - support for any window resolutions and optional panning within the maximum
76 pixel area of image sensor;
77 - image downscaling with arbitrary scaling factors from 1 and 2 in both
78 directions (see "Notes for V4L2 application developers" paragraph);
79 - two different video formats for uncompressed or compressed data in low or
80 high compression quality (see also "Notes for V4L2 application developers"
81 paragraph);
82 - full support for the capabilities of every possible image sensors that can
83 be connected to the ET61X[12]51 bridges, including, for instance, red, green,
84 blue and global gain adjustments and exposure control (see "Supported
85 devices" paragraph for details);
86 - use of default color settings for sunlight conditions;
87 - dynamic I/O interface for both ET61X[12]51 and image sensor control (see
88 "Optional device control through 'sysfs'" paragraph);
89 - dynamic driver control thanks to various module parameters (see "Module
90 parameters" paragraph);
91 - up to 64 cameras can be handled at the same time; they can be connected and
92 disconnected from the host many times without turning off the computer, if
93 the system supports hotplugging;
94 - no known bugs.
97 5. Module dependencies
98 ======================
99 For it to work properly, the driver needs kernel support for Video4Linux and
100 USB.
102 The following options of the kernel configuration file must be enabled and
103 corresponding modules must be compiled:
105 # Multimedia devices
106 #
107 CONFIG_VIDEO_DEV=m
109 To enable advanced debugging functionality on the device through /sysfs:
111 # Multimedia devices
112 #
113 CONFIG_VIDEO_ADV_DEBUG=y
115 # USB support
116 #
117 CONFIG_USB=m
119 In addition, depending on the hardware being used, the modules below are
120 necessary:
122 # USB Host Controller Drivers
123 #
124 CONFIG_USB_EHCI_HCD=m
125 CONFIG_USB_UHCI_HCD=m
126 CONFIG_USB_OHCI_HCD=m
128 And finally:
130 # USB Multimedia devices
131 #
132 CONFIG_USB_ET61X251=m
135 6. Module loading
136 =================
137 To use the driver, it is necessary to load the "et61x251" module into memory
138 after every other module required: "videodev", "v4l2_common", "compat_ioctl32",
139 "usbcore" and, depending on the USB host controller you have, "ehci-hcd",
140 "uhci-hcd" or "ohci-hcd".
142 Loading can be done as shown below:
144 [root@localhost home]# modprobe et61x251
146 At this point the devices should be recognized. You can invoke "dmesg" to
147 analyze kernel messages and verify that the loading process has gone well:
149 [user@localhost home]$ dmesg
152 7. Module parameters
153 ====================
154 Module parameters are listed below:
155 -------------------------------------------------------------------------------
156 Name: video_nr
157 Type: short array (min = 0, max = 64)
158 Syntax: <-1|n[,...]>
159 Description: Specify V4L2 minor mode number:
160 -1 = use next available
161 n = use minor number n
162 You can specify up to 64 cameras this way.
163 For example:
164 video_nr=-1,2,-1 would assign minor number 2 to the second
165 registered camera and use auto for the first one and for every
166 other camera.
167 Default: -1
168 -------------------------------------------------------------------------------
169 Name: force_munmap
170 Type: bool array (min = 0, max = 64)
171 Syntax: <0|1[,...]>
172 Description: Force the application to unmap previously mapped buffer memory
173 before calling any VIDIOC_S_CROP or VIDIOC_S_FMT ioctl's. Not
174 all the applications support this feature. This parameter is
175 specific for each detected camera.
176 0 = do not force memory unmapping
177 1 = force memory unmapping (save memory)
178 Default: 0
179 -------------------------------------------------------------------------------
180 Name: frame_timeout
181 Type: uint array (min = 0, max = 64)
182 Syntax: <n[,...]>
183 Description: Timeout for a video frame in seconds. This parameter is
184 specific for each detected camera. This parameter can be
185 changed at runtime thanks to the /sys filesystem interface.
186 Default: 2
187 -------------------------------------------------------------------------------
188 Name: debug
189 Type: ushort
190 Syntax: <n>
191 Description: Debugging information level, from 0 to 3:
192 0 = none (use carefully)
193 1 = critical errors
194 2 = significant information
195 3 = more verbose messages
196 Level 3 is useful for testing only, when only one device
197 is used at the same time. It also shows some more information
198 about the hardware being detected. This module parameter can be
199 changed at runtime thanks to the /sys filesystem interface.
200 Default: 2
201 -------------------------------------------------------------------------------
204 8. Optional device control through "sysfs"
205 ==========================================
206 If the kernel has been compiled with the CONFIG_VIDEO_ADV_DEBUG option enabled,
207 it is possible to read and write both the ET61X[12]51 and the image sensor
208 registers by using the "sysfs" filesystem interface.
210 There are four files in the /sys/class/video4linux/videoX directory for each
211 registered camera: "reg", "val", "i2c_reg" and "i2c_val". The first two files
212 control the ET61X[12]51 bridge, while the other two control the sensor chip.
213 "reg" and "i2c_reg" hold the values of the current register index where the
214 following reading/writing operations are addressed at through "val" and
215 "i2c_val". Their use is not intended for end-users, unless you know what you
216 are doing. Remember that you must be logged in as root before writing to them.
218 As an example, suppose we were to want to read the value contained in the
219 register number 1 of the sensor register table - which is usually the product
220 identifier - of the camera registered as "/dev/video0":
222 [root@localhost #] cd /sys/class/video4linux/video0
223 [root@localhost #] echo 1 > i2c_reg
224 [root@localhost #] cat i2c_val
226 Note that if the sensor registers cannot be read, "cat" will fail.
227 To avoid race conditions, all the I/O accesses to the files are serialized.
230 9. Supported devices
231 ====================
232 None of the names of the companies as well as their products will be mentioned
233 here. They have never collaborated with the author, so no advertising.
235 From the point of view of a driver, what unambiguously identify a device are
236 its vendor and product USB identifiers. Below is a list of known identifiers of
237 devices mounting the ET61X[12]51 PC camera controllers:
239 Vendor ID Product ID
240 --------- ----------
241 0x102c 0x6151
242 0x102c 0x6251
243 0x102c 0x6253
244 0x102c 0x6254
245 0x102c 0x6255
246 0x102c 0x6256
247 0x102c 0x6257
248 0x102c 0x6258
249 0x102c 0x6259
250 0x102c 0x625a
251 0x102c 0x625b
252 0x102c 0x625c
253 0x102c 0x625d
254 0x102c 0x625e
255 0x102c 0x625f
256 0x102c 0x6260
257 0x102c 0x6261
258 0x102c 0x6262
259 0x102c 0x6263
260 0x102c 0x6264
261 0x102c 0x6265
262 0x102c 0x6266
263 0x102c 0x6267
264 0x102c 0x6268
265 0x102c 0x6269
267 The following image sensors are supported:
269 Model Manufacturer
270 ----- ------------
271 TAS5130D1B Taiwan Advanced Sensor Corporation
273 All the available control settings of each image sensor are supported through
274 the V4L2 interface.
277 10. Notes for V4L2 application developers
278 =========================================
279 This driver follows the V4L2 API specifications. In particular, it enforces two
280 rules:
282 - exactly one I/O method, either "mmap" or "read", is associated with each
283 file descriptor. Once it is selected, the application must close and reopen the
284 device to switch to the other I/O method;
286 - although it is not mandatory, previously mapped buffer memory should always
287 be unmapped before calling any "VIDIOC_S_CROP" or "VIDIOC_S_FMT" ioctl's.
288 The same number of buffers as before will be allocated again to match the size
289 of the new video frames, so you have to map the buffers again before any I/O
290 attempts on them.
292 Consistently with the hardware limits, this driver also supports image
293 downscaling with arbitrary scaling factors from 1 and 2 in both directions.
294 However, the V4L2 API specifications don't correctly define how the scaling
295 factor can be chosen arbitrarily by the "negotiation" of the "source" and
296 "target" rectangles. To work around this flaw, we have added the convention
297 that, during the negotiation, whenever the "VIDIOC_S_CROP" ioctl is issued, the
298 scaling factor is restored to 1.
300 This driver supports two different video formats: the first one is the "8-bit
301 Sequential Bayer" format and can be used to obtain uncompressed video data
302 from the device through the current I/O method, while the second one provides
303 "raw" compressed video data (without frame headers not related to the
304 compressed data). The current compression quality may vary from 0 to 1 and can
305 be selected or queried thanks to the VIDIOC_S_JPEGCOMP and VIDIOC_G_JPEGCOMP
306 V4L2 ioctl's.
309 11. Contact information
310 =======================
311 The author may be contacted by e-mail at <luca.risolia@studio.unibo.it>.
313 GPG/PGP encrypted e-mail's are accepted. The GPG key ID of the author is
314 'FCE635A4'; the public 1024-bit key should be available at any keyserver;
315 the fingerprint is: '88E8 F32F 7244 68BA 3958 5D40 99DA 5D2A FCE6 35A4'.