Help? Xinerama with two cards

[David Iannucci]

Hi all,

I'm trying to set up a xinerama arrangement over two graphics cards
(Intel + Radeon), taking advantage of xrandr 1.4's features which (I
understand, perhaps mistakenly, to) support this configuration. I'm
running xorg server 1.13.4 on Gentoo. It might be useful for you to know
in addition that I'm running a barebones KDE 3.5.10 desktop on it.

If I do --listproviders, I get both cards listed:

# xrandr --listproviders
Providers: number : 2
Provider 0: id: 0x87 cap: 0xb, Source Output, Sink Output, Sink Offload
crtcs: 3 outputs: 3 associated providers: 0 name:Intel
Provider 1: id: 0x57 cap: 0xd, Source Output, Source Offload, Sink
Offload crtcs: 6 outputs: 2 associated providers: 0 name:radeon

However no use of --setprovideroutputsource or --setprovideroffloadsink
(with arguments "0 1" or "1 0") will do what I want.  Am I completely
misunderstanding this?

One monitor is connected to VGA output of integrated Intel GPU, and the
other to DVI output of Radeon (HD 7570) PCI card.  I think kernel stuff
is set up properly:

# lsmod | grep radeon
radeon                858404  1
cfbfillrect             3714  2 i915,radeon
cfbimgblt               2039  2 i915,radeon
ttm                    58739  1 radeon
cfbcopyarea             3350  2 i915,radeon
drm_kms_helper         26569  2 i915,radeon
fb                     33637  6
i915,fbcon,drm_kms_helper,radeon,softcursor,bitblit
backlight               4248  2 video,radeon

Please document this functionality more clearly! Any help with this will
be much appreciated. I can try to end-run the problem by asking my boss
to buy me an HDMI-capable monitor, to plug into the second port of Intel
card, but I've already got the Radeon, and I'd rather try to figure this
out before throwing money at it :-) Thx.

Dave