# Re: \[PATCH\] Added backlight driver for Acer Aspire 4736

- From: joeyli \<jlee@suse.com\>
- Date: 2012-03-23 04:27:48 
- List: linux-fbdev
- Page: https://ratatoskr.run/linux-fbdev/2012/03/3840039
- Thread: https://ratatoskr.run/linux-fbdev/2012/03/3835160/t.md

```text
於 五，2012-03-23 於 09:06 +0530，Pradeep Subrahmanion 提到：
> On Wed, 2012-03-21 at 11:00 +0800, joeyli wrote:
> > think the hotkey of backlight control only works with acpi_osi=Linux ?
> 
> yes , hot key control only works with this option.Any ideas about where
> the hot key events gets handled ? I tried logging inside
> 'acpi_video_device_notify' method in video.c . But the control does not
> seem to reach here . 
> 
> Thanks, 
> 
> Pradeep Subrahmanion

Hotkey change status is through _Q11 and _Q12 event but not wmi:


    Method (_Q11, 0, NotSerialized)             /* Brightness down */
    {
        If (LGreaterEqual (OSYS, 0x07D6))       /* Vista or later */
        {
            If (LEqual (OBV, 0xFF))
            {
                Notify (^^^PEGP.VGA.LCD, 0x87)
            }
            Else
            {
                Notify (^^^OVGA.DD03, 0x87)
            }
        }
        Else                                    /* 0x07D1 (XP) or 0x03E8 (Linux) */
        {
            ^^^OVGA.AINT (One, BRTS)		/* access AINT, it touch BCLP register */
            If (LEqual (^^^WMID.BAEF, One))
            {
                Store (BRTS, Local1)
                Store (^^^WMID.LBL0, Local2)
                Add (Local2, Local1, Local2)
                Store (Local2, ^^^WMID.NTDC)
                Notify (WMID, 0x80)
            }
        }
    }

Method (AINT, 2, NotSerialized)
{
...
    Else
    {
        If (LEqual (Arg0, One))         /* Linux or XP */
        {
            Add (Arg1, One, Arg1)
            Store (Divide (Multiply (Arg1, 0xFF), 0x0A, ), BCLP)
            Or (BCLP, 0x80000000, BCLP)		/* touch BCLP register */
            Store (0x02, ASLC)
        }


That's why I said acpi_osi"!Windows 2006" should also works to you. Unfortunately,
there have something wrong in video driver for support this machine on XP mode.


thanks a lot!
Joey Lee

```