Ubuntu
gnome-power-manager package

  1. Bug #376924
  2. Comment #11

Comment 11 for bug 376924

Revision history for this message
Dmitriy Geels (dmig) wrote :

Just disassembled laptop's DSDT, there a 3 device LCDD descriptors. All have method _BCL.
First 2 instances:
Device (LCDD)
{
...
Method (_BCL, 0, NotSerialized)
{
    Return (Package (0x10)
    {
        0x0F,
        0x0E,
        0x0D,
        0x0C,
        0x0B,
        0x0A,
        0x09,
        0x08,
        0x07,
        0x06,
        0x05,
        0x04,
        0x03,
        0x02,
        One,
        Zero
    })
}
...
}
And here is third one:
Device (LCDD)
{
...
Method (_BCL, 0, NotSerialized)
{
    Return (Package (0x09)
    {
        0x08,
        0x07,
        0x06,
        0x05,
        0x04,
        0x03,
        0x02,
        One,
        Zero
    })
}
...
}

As far as I understand, this causes backlight control problems and modifying first 2 instances to be like 3d one will fix problem without kernel modification (by overriding DSDT in initrd)?