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- .. 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.
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