VBIOS can't switch to external device when I use xf86-video-ati driver

[Jhih-Sin Chen]

Hi,

I am using Radeon HD 3470 card with xf86-video-ati 6.8.192 on my laptop.
I try to implement hotkey function to switch display device.
I have set _DOS parameter in ACPI and ask VBIOS to switch display
device but it fails.

However, the hotkey function can switch display device successfully
when I use "vesa" driver.
Do you have any suggetion on this issue? Thanks.