Multi screen and graphics cards failed with radeon driver on debian stretch

[Michel Dänzer]

On 30/06/17 10:53 PM, pbasnews-deb at yahoo.fr wrote:
> Without xorg.conf, I have only one half of screen. I can enable 2 screens of same
> graphics card with xrandr of course (and kde system setting too)
> 
> But unfortunaly I can not use xrand to enable my 3rd screen connected on my second
> graphic cars
> DISPLAY=:1 /usr/bin/xrandr --output VGA-0 --mode 1280x1024
> and
> DISPLAY=:1 xrandr --setprovideroutputsource "ATI Radeon 3000 Graphics @ pci:0000:01:05.0"
> 
> return is: "Can't open display :1"

[...]

> What do you mean by "Oops, the DISPLAY=:1 wasn't supposed to be there." ?

It means you should run just

 xrandr --setprovideroutputsource "ATI Radeon 3000 Graphics @ pci:0000:01:05.0" "ATI Radeon X1550 64-bit @ pci:0000:02:00.0"


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer