diff options
Diffstat (limited to 'Documentation/admin-guide/media/cafe_ccic.rst')
| -rw-r--r-- | Documentation/admin-guide/media/cafe_ccic.rst | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/Documentation/admin-guide/media/cafe_ccic.rst b/Documentation/admin-guide/media/cafe_ccic.rst new file mode 100644 index 000000000000..ff7fbce1342a --- /dev/null +++ b/Documentation/admin-guide/media/cafe_ccic.rst @@ -0,0 +1,62 @@ +.. SPDX-License-Identifier: GPL-2.0 + +The cafe_ccic driver +==================== + +Author: Jonathan Corbet <corbet@lwn.net> + +Introduction +------------ + +"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: + +.. code-block:: none + + $ 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. + +Load time options +----------------- + +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. |