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62 lines
2.5 KiB
62 lines
2.5 KiB
.. SPDX-License-Identifier: GPL-2.0 |
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The cafe_ccic driver |
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==================== |
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Author: Jonathan Corbet <[email protected]> |
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Introduction |
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------------ |
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"cafe_ccic" is a driver for the Marvell 88ALP01 "cafe" CMOS camera |
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controller. This is the controller found in first-generation OLPC systems, |
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and this driver was written with support from the OLPC project. |
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Current status: the core driver works. It can generate data in YUV422, |
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RGB565, and RGB444 formats. (Anybody looking at the code will see RGB32 as |
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well, but that is a debugging aid which will be removed shortly). VGA and |
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QVGA modes work; CIF is there but the colors remain funky. Only the OV7670 |
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sensor is known to work with this controller at this time. |
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To try it out: either of these commands will work: |
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.. code-block:: none |
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$ mplayer tv:// -tv driver=v4l2:width=640:height=480 -nosound |
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$ mplayer tv:// -tv driver=v4l2:width=640:height=480:outfmt=bgr16 -nosound |
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The "xawtv" utility also works; gqcam does not, for unknown reasons. |
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Load time options |
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----------------- |
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There are a few load-time options, most of which can be changed after |
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loading via sysfs as well: |
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- alloc_bufs_at_load: Normally, the driver will not allocate any DMA |
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buffers until the time comes to transfer data. If this option is set, |
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then worst-case-sized buffers will be allocated at module load time. |
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This option nails down the memory for the life of the module, but |
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perhaps decreases the chances of an allocation failure later on. |
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- dma_buf_size: The size of DMA buffers to allocate. Note that this |
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option is only consulted for load-time allocation; when buffers are |
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allocated at run time, they will be sized appropriately for the current |
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camera settings. |
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- n_dma_bufs: The controller can cycle through either two or three DMA |
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buffers. Normally, the driver tries to use three buffers; on faster |
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systems, however, it will work well with only two. |
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- min_buffers: The minimum number of streaming I/O buffers that the driver |
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will consent to work with. Default is one, but, on slower systems, |
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better behavior with mplayer can be achieved by setting to a higher |
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value (like six). |
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- max_buffers: The maximum number of streaming I/O buffers; default is |
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ten. That number was carefully picked out of a hat and should not be |
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assumed to actually mean much of anything. |
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- flip: If this boolean parameter is set, the sensor will be instructed to |
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invert the video image. Whether it makes sense is determined by how |
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your particular camera is mounted.
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