[PATCH] modes: Force output modes for manually enabled heads
aplattner at nvidia.com
Thu Oct 8 13:29:03 PDT 2009
On Thu, Oct 08, 2009 at 01:09:43PM -0700, Adam Jackson wrote:
> On Thu, 2009-10-08 at 10:44 -0700, Aaron Plattner wrote:
> > On Thu, Oct 08, 2009 at 10:09:20AM -0700, Keith Packard wrote:
> > > Excerpts from Chris Wilson's message of Thu Oct 08 09:43:16 -0700 2009:
> > > > In a headless configuration, in order to convince the XServer to start
> > > > the user must explicitly enable an output.
> > >
> > > I see that as the fundemental problem here. I'd suggest that the
> > > server should allow the device to start without any outputs connected
> > > and create a default sized frame buffer (1024x768?).
> > For boards that actually have output connectors (i.e. not Tesla cards),
> > this is a bad idea. The number of users who actually want a headless
> > configuration is much smaller than the number of users who would be
> > confused and infuriated when starting X makes all of their displays go
> > blank due to misconfiguration or driver bugs and results in what is
> > essentially a hung machine.
> > X failing to start with an informative log message is far better than a
> > frozen computer that requires the reset button to fix. I think making
> > people explicitly configure X to be headless is a reasonable compromise.
> Disagree. Servers regularly start with no monitor attached and admins
> expect to be able to walk up and plug in a display and have it work.
How do you propose having that happen? Having X autodetect hotplugged
screens and automatically extend the desktop to them? Does that work
If you're talking about always driving a VGA port and hoping the monitor
can support the signal it's driving, then that still requires a display
device at startup and manual configuration of the mode because there's no
I think we need to choose between the following:
1. Allow X to start with no displays. Automatically light them up when
they're plugged in (from within the server -- don't rely on a client to
do that). Make damn sure that display hotplug detection is 100%
reliable, even for VGA.
2. Fail to start X unless we're reasonably sure that the user will be able
to see something.
I don't think any combination of the two is acceptible because it can lead
to what are essentially broken computers.
> Presumably this implies moving to a model where X is started as a
> trigger from the kernel seeing a connected output, and not the current
> "start and hope".
No, in that case, failing to start X if it can't manage to find the display
the kernel detected is *still* the right behavior.
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