This commit was manufactured by cvs2svn to create branch 'vserver'.

[linux-2.6.git] / Documentation / video4linux / cafe_ccic

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+"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