video: emul: virtual driver for an imager and RX engine

[josuah]

This takes inspiration on the other skeleton.c drivers through Zephyr tree:
https://github.com/zephyrproject-rtos/zephyr/blob/main/drivers/usb/udc/udc_skeleton.c
https://github.com/zephyrproject-rtos/zephyr/blob/main/drivers/display/display_dummy.c

It acts as a starting point and as a puppet to explain API changes affecting image sensors.

Be used for providing test cases for the entire API, as required for stable APIs.

A video_get_format_index() utility is introduced in the process to find the index of a format inside a capability list.

-> What should the ideal sensor driver look like?

Fixes: #73867

[josuah]

I note that the frame interval API was merged, this will need to include it.

• Video : Add frame interval APIs #72254

[josuah]

• Aims to cover the most frequent use-cases and facilitate modifications on top
• Assume that image sensor drivers are apply modes described by pixelformat+resolution+framerate
• For every new sensor, require filling a few tables and let the ready-made functions hook them to the Zephyr video API

[josuah]

force-push: fix a bug when actually trying to compile it... It shows how important it is to provide code that actually compile, and why not as well: actually run.

[josuah]

Here is a new WIP approach. Instead of having a skeleton driver that might not compile, and past this might still have bugs, here is a pair of virtual drivers:

• MIPI RX which emulates a MIPI RX core.
• Imager which emulates an image sensor

There is a memcpy() call to pass data from the Imager to the MIPI RX other than that, everything is implemented like it would on real hardware, example of complete implementation of existing and proposed APIs (i.e. in PRs).

Next, I need to add ztests, and see if that permits to run the samples on native_sim.

[josuah]

force-push: add unit tests for the generic video_common.h utilities except video_closest_frmival(), taking a struct device * as argument.

[josuah]

force-push: unit tests for the emulated drivers: this covers the entire video API except set_signal()

To test: west twister --inline-logs --platform native_sim --scenario tests/drivers/video/api/drivers.video.api

[ngphibang]

@josuah : Is the PR ready for review ? Sorry, I asked because I received email notifications of the continuous force-push rather often that make me thinking that this is in development phase. If so, is it better to limit the force push not only to avoid email notifications but also to reduce Zephyr CI kicked-off burden for every push ? If it's not the case, it's OK to do that.

[josuah]

@ngphibang you are right, I should work on a separate wip branch and force-push there instead of directly to the PR branch. Thank you for letting me know. Yes this is ready. Twister, check_compliance, and doc build worked locally.

[EDIT: this was thought as being ready at first, and then I thought "let's add unit tests to the same PR", and then "lets' add some more", etc: I should take some time to let things mature and be more reasonable]

[josuah]

force-push:

• Fix 2 commits being mixed-up
• Fix bindings and deviceetree (include i2c-device.yaml or base.yaml)
• Use devicetree macros API like in drivers: video: Add endpoint DT helpers #80649
• Move video-common.h to video.h as the helpers are usable by the application too.

[josuah]

force-push:

• Doc build fix
• Increment the minor API version as documented. I just found out about this page! This might need an entry in https://github.com/zephyrproject-rtos/zephyr/tree/main/doc/releases for v4.1