| .. 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. |
