Display specification

[Alex Deucher]

On Mon, 14 Mar 2005 12:30:42 -0500, Adam Jackson <ajax at nwnk.net> wrote:
> On Monday 14 March 2005 12:10, Brian Paul wrote:
> > Adam Jackson wrote:
> > > So we want a device specifier.  Are PCI strings good enough?
> > >
> > > EGLDisplay dpy = eglGetDisplayForWidgetXXX("pci/0000:01:00.0");
> > >
> > > As long as there's a unique identifier for a device on a given bus, this
> > > works, so basically that's everything except ISA.  Not very GL-ish to
> > > pass a string in as an argument, I suppose.
> >
> > The sample code I'm working on does something like that.  I think it
> > would be acceptable to pass a string.  Could we also have a more
> > general syntax, like "screen/0" or "screen/1"?  That way we wouldn't
> > tie the interface to PCI-based devices.
> 
> Sure, we probably should.  The reason for the pci/ part was so we could map
> this to other bus types.  MCA, SBus, and NuBus have addressable slots.  VLB
> and ISA don't, but there you could just say isa/0 and just live with only
> supporting on device on the ISA bus.  (Not that I know of any NuBus cards
> with 3D engines, but you may want to drive them with Mesa's swrast anyway.)
> 
> Bus-addresses are admittedly user-hostile.  So we need a mapping between
> 'screen/0' and 'pci/01:00.0'.  And we can't just push that down into the
> driver because the driver we choose is based on the screen we're asking for.
> Neither do I really want an implicit mapping that depends on the order you
> walk the bus, because that can change (firmware upgrades, hotplugged cards,
> USB and PCMCIA displays).

Also on the subject of hotplug stuff, this scenario mght be nice:
walk into a conference room with a big screen connected to a
remotehost.  you connect to the LAN and you get a message, "remote
display remotehost:/pci/01:00.0" is available would you like to
connect to or extent your desktop onto this screen?"  How woudl this
screen be accessed?  Perhaps that is beyond the scope of this API...

Alex

> 
> Maybe that means a config file somewhere.  Anyway, nailing down the screen/ to
> bus address mapping isn't necessarily something we need to formalize within
> the API.
> 
> > The way I was thinking of it was:
> >   - each card corresponds to an EGLDisplay
> >   - an EGLDisplay may have one or more screens (i.e. pieces of glass)
> >   - each screen may be a view onto different surface, or the same surface.
> 
> That sounds right to me.
> 
> - ajax
> 
> 
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