default or selected kernelversion does not have config value CONFIG_AD7944.
Result is shown for kernelversion 6.9.8

Analog Devices AD7944 and similar ADCs driver

modulename: ad7944.ko

configname: CONFIG_AD7944

Linux Kernel Configuration
└─>Device Drivers
└─>Industrial I/O support
└─>Analog to digital converters
└─>SPI support
└─>Analog Devices AD7944 and similar ADCs driver
In linux kernel since version 4.19.318 (release Date: 2024-07-18)  
Say yes here to build support for Analog Devices
AD7944, AD7985, AD7986 ADCs.

To compile this driver as a module, choose M here: the
module will be called ad7944

source code: