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

Sharp SL-6000 Backlight Driver

modulename: tosa_bl.ko

configname: CONFIG_BACKLIGHT_TOSA

Linux Kernel Configuration
└─>Device Drivers
└─>Graphics support
└─>Backlight & LCD device support
└─>Sharp SL-6000 Backlight Driver
In linux kernel since version 2.6.28 (release Date: 2008-12-24)  
If you have an Sharp SL-6000 Zaurus say Y to enable a driver
for its backlight

source code: