CONFIG_IXP4XX_NPE is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
IXP4xx Network Processor Engine support
modulename: ixp4xx_npe.ko
configname: CONFIG_IXP4XX_NPE
Linux Kernel Configuration
└─>Intel IXP4xx Implementation Options
└─>IXP4xx Network Processor Engine support
In linux kernel since version 2.6.25 (release Date: 2008-04-16)
This driver supports IXP4xx built-in network coprocessors
and is automatically selected by Ethernet and HSS drivers.
and is automatically selected by Ethernet and HSS drivers.