| "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 |