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diff --git a/Documentation/admin-guide/media/raspberrypi-rp1-cfe.rst b/Documentation/admin-guide/media/raspberrypi-rp1-cfe.rst new file mode 100644 index 000000000000..668d978a9875 --- /dev/null +++ b/Documentation/admin-guide/media/raspberrypi-rp1-cfe.rst @@ -0,0 +1,78 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================================ +Raspberry Pi PiSP Camera Front End (rp1-cfe) +============================================ + +The PiSP Camera Front End +========================= + +The PiSP Camera Front End (CFE) is a module which combines a CSI-2 receiver with +a simple ISP, called the Front End (FE). + +The CFE has four DMA engines and can write frames from four separate streams +received from the CSI-2 to the memory. One of those streams can also be routed +directly to the FE, which can do minimal image processing, write two versions +(e.g. non-scaled and downscaled versions) of the received frames to memory and +provide statistics of the received frames. + +The FE registers are documented in the `Raspberry Pi Image Signal Processor +(ISP) Specification document +<https://datasheets.raspberrypi.com/camera/raspberry-pi-image-signal-processor-specification.pdf>`_, +and example code for FE can be found in `libpisp +<https://github.com/raspberrypi/libpisp>`_. + +The rp1-cfe driver +================== + +The Raspberry Pi PiSP Camera Front End (rp1-cfe) driver is located under +drivers/media/platform/raspberrypi/rp1-cfe. It uses the `V4L2 API` to register +a number of video capture and output devices, the `V4L2 subdev API` to register +subdevices for the CSI-2 received and the FE that connects the video devices in +a single media graph realized using the `Media Controller (MC) API`. + +The media topology registered by the `rp1-cfe` driver, in this particular +example connected to an imx219 sensor, is the following one: + +.. _rp1-cfe-topology: + +.. kernel-figure:: raspberrypi-rp1-cfe.dot + :alt: Diagram of an example media pipeline topology + :align: center + +The media graph contains the following video device nodes: + +- rp1-cfe-csi2-ch0: capture device for the first CSI-2 stream +- rp1-cfe-csi2-ch1: capture device for the second CSI-2 stream +- rp1-cfe-csi2-ch2: capture device for the third CSI-2 stream +- rp1-cfe-csi2-ch3: capture device for the fourth CSI-2 stream +- rp1-cfe-fe-image0: capture device for the first FE output +- rp1-cfe-fe-image1: capture device for the second FE output +- rp1-cfe-fe-stats: capture device for the FE statistics +- rp1-cfe-fe-config: output device for FE configuration + +rp1-cfe-csi2-chX +---------------- + +The rp1-cfe-csi2-chX capture devices are normal V4L2 capture devices which +can be used to capture video frames or metadata received from the CSI-2. + +rp1-cfe-fe-image0, rp1-cfe-fe-image1 +------------------------------------ + +The rp1-cfe-fe-image0 and rp1-cfe-fe-image1 capture devices are used to write +the processed frames to memory. + +rp1-cfe-fe-stats +---------------- + +The format of the FE statistics buffer is defined by +:c:type:`pisp_statistics` C structure and the meaning of each parameter is +described in the `PiSP specification` document. + +rp1-cfe-fe-config +----------------- + +The format of the FE configuration buffer is defined by +:c:type:`pisp_fe_config` C structure and the meaning of each parameter is +described in the `PiSP specification` document. |