Writing new camera driver for i.mx8mp -- questions

[DWSmith]

I'm working on trying to get video in via MIPI-CSI to the i.mx8MPlus...starting with the EVK (8MPLUS-BB) and later moving to a custom PCB.

My image sensor is a Sony imx287, for which there currently exists no public driver outside of modules that have integrated it with an ASIC and control it through the ASIC.  Fortunately, I have the datasheet & list of extra initialization registers from our parts vendor and have a good idea how to basically control it over I2C.

In my case, we are putting down the raw sensor with custom optics (no Bayer filter--we essentially use the sensor in monochrome) and convert the Sony sub-LVDS output to MIPI-CSI2 via a Lattice FPGA.

Our (initial) needs for control are pretty basic. We just want to initialize the camera to run all-pixel, at maximum framerate, with 10-bit RAW output, and just control start & stop streaming. Later, we will probably add external trigger control for affecting exposure, and maybe blacklevel & gain controls.

The initial plan before I was brought onto the project was to control the sensor via I2C from the M7 core, with the video output via the Lattice bridge into the 1st CSI port on the i.mx8mp, and use GStreamer on an A53 core to pick up the stream and either save off images or ship the stream over the network.

That is where I joined the project. Nobody had a plan for how to setup the MIPI input--I think it was just assumed that GStreamer would hook up to the MIPI port & data would flow when you told the sensor to start streaming. I realized there was a need for an actual Linux camera driver, as Gstreamer
needs to talk to a device.

So we are moving the I2C peripheral to the A53 to allow a more proper Linux camera driver.
I started digging into V4L2, which I have never written for before. I had a look at the I.MX8MPLUS camera sensor porting guide and see reference to "vvcam" and the ISI and ISP, and some need for an xml file to describe the Bayer filter (we have none) and lens parameters, etc.
This all seems much more complicated than just a V4L2 sub-device & a device-tree file to inform that the sub-device utilizes the MIPI-CSI1 port on the i.mx8mplus.

So my 1st set of questions are:

1) is it required to utilize the ISI and Vivante ISP? Or can it be a simple as a "standard" V4L2 sub-device (mostly an i2c driver with the hooks that V4L2 needs and ioctl defs, etc.) with a dts file to "wire it up"?
2) if Vivante ISP is required, what do you do if you are operating without a Bayer filter and don't want anything done about lens parameters (dewarp, etc.)? I just want the raw 10-bit images. We have a PC-based application that processes those later.

Many thanks for any guidance you can provide.