default or selected kernelversion does not have config value CONFIG_I2O_EXT_ADAPTEC.
Result is shown for kernelversion 6.5.1

Enable Adaptec extensions

configname: CONFIG_I2O_EXT_ADAPTEC

Linux Kernel Configuration
└─>Device Drivers
└─>I2O device support
└─>Enable Adaptec extensions
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
Say Y for support of raidutils for Adaptec I2O controllers. You also
have to say Y to "I2O Configuration support", "I2O SCSI OSM" below
and to "SCSI generic support" under "SCSI device configuration".

depends
CONFIG_I2O