default or selected kernelversion does not have config value CONFIG_VIDEO_STM32_CSI.
Result is shown for kernelversion 6.6.78

STM32 Camera Serial Interface (CSI) support

modulename: stm32-csi.ko

configname: CONFIG_VIDEO_STM32_CSI

Linux Kernel Configuration
└─>Device Drivers
└─>Multimedia support
└─>Media drivers
└─>Media platform devices
└─>Device Tree and Open Firmware support
└─>STM32 Camera Serial Interface (CSI) support
In linux kernel since version 6.6.78 (release Date: 2025-02-17)  
This module makes the STM32 Camera Serial Interface (CSI)
available as a v4l2 device.

To compile this driver as a module, choose M here: the module
will be called stm32-csi.

source code:
drivers/media/platform//st/stm32/stm32-csi.c