default or selected kernelversion does not have config value CONFIG_CAIF_SPI_SLAVE.
Result is shown for kernelversion 6.8.2

CAIF SPI transport driver for slave interface

modulename: cfspi_slave.ko


Linux Kernel Configuration
└─>Device Drivers
└─>Network device support
└─>CAIF SPI transport driver for slave interface
In linux kernel since version 2.6.36 (release Date: 2010-10-20)  
The CAIF Link layer SPI Protocol driver for Slave SPI interface.
This driver implements a platform driver to accommodate for a
platform specific SPI device. A sample CAIF SPI Platform device is
provided in
source code: