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author | Jonathan Corbet <corbet-v4l@lwn.net> | 2006-11-04 15:25:53 +0300 |
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committer | Mauro Carvalho Chehab <mchehab@infradead.org> | 2006-12-10 13:51:13 +0300 |
commit | d905b382d797a213e15868cbf3204f50ed52e30b (patch) | |
tree | 9e328aa8e273bcc0656cd0bb4a51020ea10ef008 /Documentation | |
parent | 9c4dfadbde3cfa78b92c28597125b8c41d36ffd0 (diff) | |
download | linux-d905b382d797a213e15868cbf3204f50ed52e30b.tar.xz |
V4L/DVB (4797): Marvell 88ALP01 "cafe" driver
A driver for the Marvell M88ALP01 "CAFE" CMOS integrated camera
controller. This driver has been renamed "cafe_ccic" since my previous
patch set.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/video4linux/cafe_ccic | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/Documentation/video4linux/cafe_ccic b/Documentation/video4linux/cafe_ccic new file mode 100644 index 000000000000..88821022a5de --- /dev/null +++ b/Documentation/video4linux/cafe_ccic @@ -0,0 +1,54 @@ +"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 |