4. Module dependencies
5. Module loading
6. Module parameters
-7. Device control through "sysfs"
+7. Optional device control through "sysfs"
8. Supported devices
9. How to add support for new image sensors
-10. Note for V4L2 developers
+10. Notes for V4L2 application developers
11. Contact information
12. Credits
1 = critical errors
2 = significant informations
3 = more verbose messages
- Level 3 is useful for testing only, when just one device
+ Level 3 is useful for testing only, when only one device
is used.
Default: 2
-------------------------------------------------------------------------------
-7. Device control through "sysfs"
-=================================
+7. Optional device control through "sysfs"
+==========================================
It is possible to read and write both the SN9C10[12] and the image sensor
registers by using the "sysfs" filesystem interface.
-Every time a supported device is recognized, read-only files named "redblue"
-and "green" are created in the /sys/class/video4linux/videoX directory. You can
-set the red, blue and green channel's gain by writing the desired value to
-them. The value may range from 0 to 15 for each channel; this means that
-"redblue" accepts 8-bit values, where the low 4 bits are reserved for red and
-the others for blue.
+Every time a supported device is recognized, a read-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.
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
0xc45 0x6029
0xc45 0x602a
0xc45 0x602c
-0xc45 0x8001
+0xc45 0x6030
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.
Model Manufacturer
----- ------------
PAS106B PixArt Imaging Inc.
+PAS202BCB PixArt Imaging Inc.
TAS5110C1B Taiwan Advanced Sensor Corporation
TAS5130D1B Taiwan Advanced Sensor Corporation
(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, not yet supported image sensors are: PAS202B (VGA),
-HV7131[D|E1] (VGA), MI03 (VGA), OV7620 (VGA).
+At the moment, not yet supported image sensors are: HV7131[D|E1] (VGA),
+MI03 (VGA), OV7620 (VGA).
-10. Note for V4L2 developers
-============================
+10. Notes for V4L2 application developers
+=========================================
This driver follows the V4L2 API specifications. In particular, it enforces two
rules:
-1) Exactly one I/O method, either "mmap" or "read", is associated with each
+- 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.
+device to switch to the other I/O method;
-2) Previously mapped buffer memory must always be unmapped before calling any
-of the "VIDIOC_S_CROP", "VIDIOC_TRY_FMT" and "VIDIOC_S_FMT" ioctl's. In case,
-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 them again before any I/O attempts.
+- previously mapped buffer memory must always be unmapped before calling any
+of the "VIDIOC_S_CROP", "VIDIOC_TRY_FMT" and "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 them again before any I/O attempts.
+
+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 choosen 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.
11. Contact information
- Stefano Mozzi, who donated 45 EU;
- Luca Capello for the donation of a webcam;
-- Mizuno Takafumi for the donation of a webcam.
+- Mizuno Takafumi for the donation of a webcam;
+- Carlos Eduardo Medaglia Dyonisio, who added the support for the PAS202BCB
+ image sensor.
git://git.onelab.eu / linux-2.6.git / blobdiff