Bug#529043: Multiseat (multiple active ServerLayout) support for dual-head cards
Package: xserver-xorg
This is a bug/missing functionality report for upstream.
Currently, a single X instance can only provide a single ServerLayout on
a single display number.
Users who want to operate multiseat configurations (where they have two
or more different ServerLayouts configured, one for each seat) must
start a different X process for each ServerLayout, and use a distinct
-layout parameter with each X instance.
For users with a dual-head or multi-head card, and a desire to split the
ports on the card between multiple seats, there is a problem: two
separate X instances, as described above, can't access the same physical
card at the same time.
The solution: a single X instance needs to be able to activate multiple
ServerLayouts, provided that none of them try to use any identical
resource. This would allow a single driver instance to attach to the
video card, and provide two independent displays (e.g. :0.0 and :1.0
instead of the more typical :0.0 and :0.1)
There are many use cases for this:
- Dual-purpose PVR/HTPC environments, where a PC is used with a regular
X display, and a TV is also controlled by the TV output from the main
video card. If the TV is driven by the same X instance as the regular
user session, then it becomes impossible to do things like switching to
a different user or locking the PC screen without losing the TV output.
With high-quality PVR software like Freevo and MythTV now available,
there will be more demand for this use case.
- two or more users who want to use a low cost PC at the same time,
saving on hardware costs, energy costs and cooling costs
- squeezing more seats out of high-density multiseat installs (the
maximum configuration right now is 1 seat for each PCI slot that can
take an independent video card, typically 5-6 seats per PC - if
dual-head cards are used, the same PC could service 10-12 seats)
Xephyr can be used as a workaround for all of these cases, but it comes
with some loss of features in X, the mouse is not as responsive as on a
native X instance, etc.
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