Re: [RFC] enhancing the kernel's graphics subsystem

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Dave Airlie wrote:
On 5/21/07, Jon Smirl <[email protected]> wrote:
On Thu, 17 May 2007 14:23:45 -0700, Jesse Barnes wrote:

> In collaboration with the FB guys, we've been working on enhancing the
> kernel's graphics subsystem in an attempt to bring some sanity to the
> Linux graphics world and avoid the situation we have now where several
> kernel and userspace drivers compete for control of graphics devices.

How is supporting different users logged into each head going to work?
The original model for this was to give each head its own fbdev device.
It is important that each user be able to set their own mode without being
root.

TThe problem with that is the concept of heads is flawed... there is
in reality no such
thing, you have crtcs and outputs, no heads. So any attempt to enforce
the head concept involves putting policy into the kernel, as if I have
3 outputs but 2 crtcs how do I decide the mappings without the admin
telling the kernel,

Solution:
One device per crtc. You can then have two users, running consoles
or xservers on their crtcs, without having to involve root.

The crtc->output mapping must still be done by root of course.

This solution allow the useful case where the computer boots, the boot scripts
set up a crtc->output mapping. Then users log in through the
various consoles (using getty or xdm or similiar) using their grahphical
devices in whatever way they want.  A true multiseat setup.


And if one user needs to use all the screens for multi-display work?
Let root change the mappings, possibly through some sudo setup.

Helge Hafting
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