How to easily swap the connector order?

[Alex Deucher]

>________________________________
> From: Ing. Daniel Rozsnyó <daniel at rozsnyo.com>
>To: Michel Dänzer <michel at daenzer.net> 
>Cc: xorg-driver-ati at lists.x.org 
>Sent: Tuesday, May 28, 2013 1:03 PM
>Subject: Re: How to easily swap the connector order?
> 
>
>On 05/28/2013 06:47 PM, Michel Dänzer wrote:
>> On Die, 2013-05-28 at 18:07 +0200, "Ing. Daniel Rozsnyó" wrote:
>>> Hi,
>>>    I am using a configuration for two heads, :0.0 and :0.1:
>>>
>>> Section "Device"
>>>          Identifier  "devDn"
>>>          Driver      "radeon"
>>>          BusID       "PCI:0:1:0"
>>>          Option      "monitor-VGA-0" "monDn"
>>>          Screen      0
>>> EndSection
>>>
>>> Section "Device"
>>>          Identifier  "devUp"
>>>          Driver      "radeon"
>>>          BusID       "PCI:0:1:0"
>>>          Option      "monitor-HDMI-0"  "monUp"
>>>          Screen      1
>>> EndSection
>>>
>>> But the HDMI is always assigned to :0.0 and the VGA port is
>>> always :0.1.
>>>
>>> How can one reverse the order of the detected connectors? I would like
>>> to have an easy option to swap the two.
>> Option "ZaphodHeads" should allow you to choose which output(s) to use
>> in which Section "Device". See the radeon manpage.
>>
>>
>
>Great, now that works:
>
>Section "Device"
>         Identifier  "devDn"
>         Driver      "radeon"
>         BusID       "PCI:0:1:0"
>         Option      "monitor-VGA-0" "monDn"
>         Option      "ZaphodHeads"   "VGA-0"
>         Screen      0
>EndSection
>
>Section "Device"
>         Identifier  "devUp"
>         Driver      "radeon"
>         BusID       "PCI:0:1:0"
>         Option      "monitor-HDMI-0"  "monUp"
>         Option      "ZaphodHeads"   "HDMI-0"
>         Screen      1
>EndSection
>
>
>Thank you. I have googled to ZaphodHeads option, but I got the feeling 
>it is is rather be used for some special purpose mode of multi-seat setup.
>So cryptic naming of the options is hell.

It has nothing to do with multi-seat.  Most people just use xrandr or whatever gui tool their distor provides to adjust displays on the fly.  The only reason you need to use an xorg.conf like above is if you want independent X screens on the same card.  For historical reasons that mode of operation is called Zaphod mode, hence ZaphodHeads.



>
>Can I leave out the monitor-* options? In xorg.conf, I still have two 
>Screen objects where the monitors and devices are linked together... not 
>sure what is the correct way today.


You only need the monitors sections if you want to force certain behavior in the monitors (e.g., rotation or specific modelines).  If your monitor sections are empty, you can skip them.  Also, you can remove the the "monitor-OUTPUT" lines from your config if you just set the monitor identifier to the name of the output.  E.g,

Section "Monitor"

    Identifier "HDMI-0"

    ...

EndSection

Alex