微電腦 - SHARP Brain PW-SH3 - Brainux - 調整預設背光亮度

參考資訊：
https://brainux.org/

$ vim arch/arm/boot/dts/imx28-pwsh3.dts
    &backlight_display {
        default-brightness-level = <5>;
        status = "okay";
    };

P.S. 編譯後的imx28-pwsh3.dtb覆蓋到MicroSD imx28-pwsh3.dtb