54 lines
2.4 KiB
Text
54 lines
2.4 KiB
Text
"cafe_ccic" is a driver for the Marvell 88ALP01 "cafe" CMOS camera
|
|
controller. This is the controller found in first-generation OLPC systems,
|
|
and this driver was written with support from the OLPC project.
|
|
|
|
Current status: the core driver works. It can generate data in YUV422,
|
|
RGB565, and RGB444 formats. (Anybody looking at the code will see RGB32 as
|
|
well, but that is a debugging aid which will be removed shortly). VGA and
|
|
QVGA modes work; CIF is there but the colors remain funky. Only the OV7670
|
|
sensor is known to work with this controller at this time.
|
|
|
|
To try it out: either of these commands will work:
|
|
|
|
mplayer tv:// -tv driver=v4l2:width=640:height=480 -nosound
|
|
mplayer tv:// -tv driver=v4l2:width=640:height=480:outfmt=bgr16 -nosound
|
|
|
|
The "xawtv" utility also works; gqcam does not, for unknown reasons.
|
|
|
|
There are a few load-time options, most of which can be changed after
|
|
loading via sysfs as well:
|
|
|
|
- alloc_bufs_at_load: Normally, the driver will not allocate any DMA
|
|
buffers until the time comes to transfer data. If this option is set,
|
|
then worst-case-sized buffers will be allocated at module load time.
|
|
This option nails down the memory for the life of the module, but
|
|
perhaps decreases the chances of an allocation failure later on.
|
|
|
|
- dma_buf_size: The size of DMA buffers to allocate. Note that this
|
|
option is only consulted for load-time allocation; when buffers are
|
|
allocated at run time, they will be sized appropriately for the current
|
|
camera settings.
|
|
|
|
- n_dma_bufs: The controller can cycle through either two or three DMA
|
|
buffers. Normally, the driver tries to use three buffers; on faster
|
|
systems, however, it will work well with only two.
|
|
|
|
- min_buffers: The minimum number of streaming I/O buffers that the driver
|
|
will consent to work with. Default is one, but, on slower systems,
|
|
better behavior with mplayer can be achieved by setting to a higher
|
|
value (like six).
|
|
|
|
- max_buffers: The maximum number of streaming I/O buffers; default is
|
|
ten. That number was carefully picked out of a hat and should not be
|
|
assumed to actually mean much of anything.
|
|
|
|
- flip: If this boolean parameter is set, the sensor will be instructed to
|
|
invert the video image. Whether it makes sense is determined by how
|
|
your particular camera is mounted.
|
|
|
|
Work is ongoing with this driver, stay tuned.
|
|
|
|
jon
|
|
|
|
Jonathan Corbet
|
|
corbet@lwn.net
|