default or selected kernelversion does not have config value CONFIG_AD799X.
Result is shown for kernelversion 6.0-rc7

Analog Devices AD799x ADC driver

modulename: ad799x.ko
configname: CONFIG_AD799X

Linux Kernel Configuration
└─> Device Drivers
└─> Industrial I/O support
└─> Analog to digital converters
└─> Analog Devices AD799x ADC driver

Say yes here to build support for Analog Devices:
ad7991, ad7995, ad7999, ad7992, ad7993, ad7994, ad7997, ad7998
i2c analog to digital converters (ADC). Provides direct access
via sysfs.

To compile this driver as a module, choose M here: the module will be
called ad799x.

source code: