My mail to ASUS.

Hallo,

On my new o UX330 i discovered issue related to Ambient Light Sensor (ALS).
On ASUS laptops ALS is usually disabled by default and BIOS provides ASUS WMI interface to set the state to enable or disable and to get current state.

On all my laptops Asus UX31A, UX302LA and UX330UA the SET function works as expected. The GET function is broken on  UX330.
After comparing BIOS DSDT of UX330 and  UX31A I found that there is a typo I the UX330 BIOS:
             Method (WMNB, 3, Serialized)
            {
            ...
               If (Local0 == 0x53545344)
                {
                ...
                    If (IIA0 == 0x00050001)
                    {
                        If (!ALSP)
                        {
                            Return (0x02)
                        }

                        Local0 = (GALS & 0x10)    <<<---- bug,
                                                    should be: (GALS () & 0x10)
                        If (Local0)
                        {
                            Return (0x00050001)
                        }
                        Else
                        {
                            Return (0x00050000)
                        }
                    }

             .....
                If (Local0 == 0x53564544)
                {
                ...
                    If (IIA0 == 0x00050001)
                    {
                        Return (ALSC (IIA1))
                    }


the same part on UX32A:
                    If ((IIA0 == 0x00050001))
                    {
                        If (!ALSP)
                        {
                            Return (0x02)
                        }

                        Local0 = (GALS () & 0x10)   <<←-- not a bug.
                        If (Local0)
                        {
                            Return (0x00050001)
                        }
                        Else
                        {
                            Return (0x00050000)
                        }
                    }

                    If ((IIA0 == 0x00050013))
                    {
                        Local0 = (GALS () & 0x0F0F)
                        Return (Local0)
                    }


Since on Linux we test GET method first and if it fails not trying to use SET method, the ASUS UX330 model has not enabled  Ambient Light Sensor.
I provided a patch to enable Ambient Light Sensor by default even if GET method will fail (with the hope it will not brake support for other ASUS devices), so this issue theoretically will be solved in coming Linux distributions.

In any case it will be good if ASUS will fix BIOS as well.

If you need more technical information pleas contact me.

Best regards,