RandR questions

Pedro DeKeratry pdekeratry at gmail.com
Thu Nov 4 15:49:52 PDT 2010


Thank you for the clarifications. Where do I go to edit the userspace
action when the digital monitor connect/disconnect interrupt is


On Tue, Nov 2, 2010 at 7:43 AM, Alex Deucher <alexdeucher at gmail.com> wrote:
> On Tue, Nov 2, 2010 at 3:01 AM, Pedro DeKeratry <pdekeratry at gmail.com> wrote:
>> First let me describe the behavior that prompted my questions. This is
>> on a laptop running Ubuntu Desktop 10.10 and the xorg.conf is
>> configured to run a mutli-display using the external HDMI and external
>> VGA ports, thus the laptop screen is blank/off. If I unplug the HDMI
>> connection the system does some display switching and my laptop screen
>> turns on. When I plug the HDMI connection back in nothing happens. A
>> couple of xrandr commands later and I can get the HDMI output
>> displaying how it was originally. Suppose though that instead of
>> issuing the xrandr commands to bring the external HDMI connection back
>> up after plugging it in, I reboot the machine instead. Since my
>> /etc/xorg.conf is unchanged I would expect that both my external
>> monitors come up, however, the laptop screen comes on instead of my
>> HDMI external connection which is now shown as disconnected. To get
>> things back the way they were I can either used xrandr like previously
>> or the ATI gfx menu options. Note that this only happens with regards
>> to my HDMI connection because I think the laptop screen and the HDMI
>> share the TMDS graphics hardware ( Assuming my understanding of these
>> things is correct ; ) .) Unplugging the VGA doesn't create any auto
>> switching response.
> Your laptop screen and hdmi port are likely using separate encoders,
> but you only have 2 display controllers so you can only use two
> displays at a time.  Digital connectors (DVI, HDMI, DP) have a hot
> plug pin that can generate an interrupt when the monitor is connected
> or disconnected, but older analog monitors (VGA, TV) do not.
>> So, with that said:
>> Is is xrandr that does the auto switching from ext. HDMI to laptop
>> automatically when HDMI monitor signal is lost? Or is that the gfx
>> drivers or some other X program? ( I'd like to disable it if possible
>> )
> When a connect/disconnect interrupt is generated the drm sends an
> event to userspace which can then do something with the event.  In
> your case I think it just runs 'xrandr --auto' when it receives the
> event, but you can have it do whatever you want.
>> Is it xrandr that is saving some kind of persistent configuration
>> settings somewhere that overrides my xorg.conf file at the next
>> reboot? I couldn't find any sort of conf file anywhere related to
>> this. Googling xrandr info doesn't show much except same man pages.
> randr does not save any persistent state.  if you want to force a
> particular setup, you need to specify it in your xorg.conf or via
> xrandr commands in your desktop startup scripts.
>> Is xrandr scheduled to replace xorg.conf altogether? I've noticed that
>> my xorg.conf really is pretty much as minimal as you can get. In
>> previous Linux systems I've had much more intricate xorg.conf files
>> with a lot more details filled in. Other than loading the driver for
>> the gfx card, it seems like everything else can be pretty much done
>> through xrandr. Am I understanding correctly where xrandr is headed in
>> the Linux/X world?
> xrandr is just a utility to dynamically reconfigure your displays.
> xorg.conf is for specifying specific settings.  See this page for info
> an using xrandr and specifying display settings in your xorg.conf:
> http://wiki.debian.org/XStrikeForce/HowToRandR12
> Alex
>> --Pedro
>> On Sat, Oct 30, 2010 at 4:03 AM, Jeremy Huddleston
>> <jeremyhu at freedesktop.org> wrote:
>>> This would be a good place...
>>> On Oct 29, 2010, at 21:07, Pedro DeKeratry wrote:
>>>> Hi everyone,
>>>> Is this the appropriate place to ask questions about the xrandr
>>>> command line utility in order to understand how it interacts with my
>>>> system environment at large or is such a question better suited to a
>>>> distro specific mailing list?
>>>> --Pedro
>>>> _______________________________________________
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