default or selected kernelversion does not have config value CONFIG_AD7779.
Result is shown for kernelversion 6.6.75

Analog Devices AD7779 ADC driver

modulename: ad7779.ko

configname: CONFIG_AD7779

Linux Kernel Configuration
└─>Device Drivers
└─>Industrial I/O support
└─>Analog to digital converters
└─>SPI support
└─>Analog Devices AD7779 ADC driver
In linux kernel since version 6.13 (release Date: 2025-01-19)  
Say yes here to build support for Analog Devices AD777X family
(AD7770, AD7771, AD7779) analog to digital converter (ADC).

To compile this driver as a module, choose M here: the module will be
called ad7779.

source code: