Commit | Line | Data |
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d905b382 JC |
1 | "cafe_ccic" is a driver for the Marvell 88ALP01 "cafe" CMOS camera |
2 | controller. This is the controller found in first-generation OLPC systems, | |
3 | and this driver was written with support from the OLPC project. | |
4 | ||
5 | Current status: the core driver works. It can generate data in YUV422, | |
6 | RGB565, and RGB444 formats. (Anybody looking at the code will see RGB32 as | |
7 | well, but that is a debugging aid which will be removed shortly). VGA and | |
8 | QVGA modes work; CIF is there but the colors remain funky. Only the OV7670 | |
9 | sensor is known to work with this controller at this time. | |
10 | ||
11 | To try it out: either of these commands will work: | |
12 | ||
13 | mplayer tv:// -tv driver=v4l2:width=640:height=480 -nosound | |
14 | mplayer tv:// -tv driver=v4l2:width=640:height=480:outfmt=bgr16 -nosound | |
15 | ||
16 | The "xawtv" utility also works; gqcam does not, for unknown reasons. | |
17 | ||
18 | There are a few load-time options, most of which can be changed after | |
19 | loading via sysfs as well: | |
20 | ||
21 | - alloc_bufs_at_load: Normally, the driver will not allocate any DMA | |
22 | buffers until the time comes to transfer data. If this option is set, | |
23 | then worst-case-sized buffers will be allocated at module load time. | |
24 | This option nails down the memory for the life of the module, but | |
25 | perhaps decreases the chances of an allocation failure later on. | |
26 | ||
27 | - dma_buf_size: The size of DMA buffers to allocate. Note that this | |
28 | option is only consulted for load-time allocation; when buffers are | |
29 | allocated at run time, they will be sized appropriately for the current | |
30 | camera settings. | |
31 | ||
32 | - n_dma_bufs: The controller can cycle through either two or three DMA | |
33 | buffers. Normally, the driver tries to use three buffers; on faster | |
34 | systems, however, it will work well with only two. | |
35 | ||
36 | - min_buffers: The minimum number of streaming I/O buffers that the driver | |
37 | will consent to work with. Default is one, but, on slower systems, | |
38 | better behavior with mplayer can be achieved by setting to a higher | |
39 | value (like six). | |
40 | ||
41 | - max_buffers: The maximum number of streaming I/O buffers; default is | |
42 | ten. That number was carefully picked out of a hat and should not be | |
43 | assumed to actually mean much of anything. | |
44 | ||
45 | - flip: If this boolean parameter is set, the sensor will be instructed to | |
46 | invert the video image. Whether it makes sense is determined by how | |
47 | your particular camera is mounted. | |
48 | ||
49 | Work is ongoing with this driver, stay tuned. | |
50 | ||
51 | jon | |
52 | ||
53 | Jonathan Corbet | |
54 | corbet@lwn.net |