Re: EDID from multiple displays using ioctl(WSDISPLAYIO_GET_EDID)

[Reinoud Zandijk <reinoud%NetBSD.org@localhost>]

On Wed, Dec 23, 2020 at 09:03:16AM +0100, Michael van Elst wrote:
> On Wed, Dec 23, 2020 at 07:36:10AM +0000, RVP wrote:
> > On Wed, 23 Dec 2020, Michael van Elst wrote:
> > 
> > > If you had multiple wsdisplay* instances, there would be some
> > > corresponding ttyE* that you could send the ioctl to.
> > 
> > Hmm: wsdisplay0 at intelfb0; wsdisplay1 at nouveaufb0 ?  What about
> > multiple multiple monitors connected to the same card?
> 
> The driver would need to create multiple instances, and I doubt that this
> works with the current code base.

The current code base for the FBs are most likely DRM backed. On NetBSD but
also on Linux, outside X, all screens connected to one card are mirrors of
eachother and thus only get one wsdisplay regretfully. That you see two is
most likely the CPU builtin GPU and the laptops GPU card.

In the ideal world I'd love to see multiple tty's on multiple screens and
being able to switch between them with the muxed keyboard but at the same time
allow X to span them all (or a set) ....

The furthest I got was a prompt on wsdisplay1 (ttyF0) but no way to switch the
keyboard to it. Also our X doesn't like to spawn over multiple display
adapters though there is support for it in X. It has to do with the missing
(and most likely completely obsolete) VGA arbiter. It is required to prevent
overlapping legacy VGA registers.

Eventually i gave up and are now running two displays on one card and have to
live with a mirror screen when not in X.

Reinoud