ASL Code Method _BCL and _BCM

1. OS will get brightness level from _BCL

Method(_BCL, 0, NotSerialized)
{
    Return(Package(){100,    // AC Default Level 16
                                  33,    // DC Default Level 5
                                  13,    // Level 1
                                  18,    // Level 2
                                  23,    // Level 3
                                  28,    // Level 4
                                  33,    // Level 5
                                  38,    // Level 6
                                  43,    // Level 7
                                  48,    // Level 8
                                  54,    // Level 9
                                  60,    // Level 10
                                  66,    // Level 11
                                  72,    // Level 12
                                  78,    // Level 13
                                  84,    // Level 14
                                  90,    // Level 15
                                 100    // Level 16
                                })
}



2. OS will set brightness from _BCM

Method(_BCM, 1, NotSerialized)
{
    if (LEqual(\_SB.PCI0.VGA.AF7E, 0x80000001)) // Brightness control by driver
    {                                        
        // Using the equation (Arg0*3+19)/20 to convert the "0 to 100%" BCL levels
        // to "0 to 15" based.
        Divide(Add(Multiply(Arg0, 3), 19), 20, Local1, Local0)
        Store (DeRefOf(Index(BLVL, Local0)), Local3) // Get 0-255 range level from buffer
         \_SB.PCI0.AFN7(Local3)
    }
}


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1. OS會從ACPI的Method _BCL去得到需要所訂定的明亮度

Method(_BCL, 0, NotSerialized)
{
    Return(Package(){100,    // AC 預設 Level 16 (預設一插上AC電源就將明亮度調至100%)
                                  33,    // DC 預設  Level 5 (預設DC電源就將明亮度調至33%)
                                  13,    // Level 1
                                  18,    // Level 2
                                  23,    // Level 3
                                  28,    // Level 4
                                  33,    // Level 5
                                  38,    // Level 6
                                  43,    // Level 7
                                  48,    // Level 8
                                  54,    // Level 9
                                  60,    // Level 10
                                  66,    // Level 11
                                  72,    // Level 12
                                  78,    // Level 13
                                  84,    // Level 14
                                  90,    // Level 15
                                 100    // Level 16
                                })
}



2. OS從ACPI的Method_BCM去設定明亮度

Method(_BCM, 1, NotSerialized)
{
    if (LEqual(\_SB.PCI0.VGA.AF7E, 0x80000001)) // Brightness control by driver
    {                                        
        // Using the equation (Arg0*3+19)/20 轉換 "0 to 100%" BCL levels至 to "0 to 15" 階.
        Divide(Add(Multiply(Arg0, 3), 19), 20, Local1, Local0)
        Store (DeRefOf(Index(BLVL, Local0)), Local3) // 從buffer抓0-255的範圍
         \_SB.PCI0.AFN7(Local3)
    }
}

_BCL和_BCM僅使用在筆記型電腦，桌上型電腦不需支援