default or selected kernelversion does not have config value CONFIG_DRM_DP_AUX_CHARDEV.
Result is shown for kernelversion 6.9.9

DRM DP AUX Interface

configname: CONFIG_DRM_DP_AUX_CHARDEV

Linux Kernel Configuration
└─>Device Drivers
└─>Graphics support
└─>Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)
└─>DRM DP AUX Interface
In linux kernel since version 3.10 (release Date: 2013-06-30)  
Choose this option to enable a /dev/drm_dp_auxN node that allows to
read and write values to arbitrary DPCD registers on the DP aux
channel.