[RFC][PATCH 0/10] Atomic modesetting v2

[Dave Airlie]

On Wed, Jun 27, 2012 at 6:11 PM, Adam Jackson <ajax at redhat.com> wrote:
> On Wed, 2012-06-27 at 09:48 -0700, Jesse Barnes wrote:
>
>> The other thing I'm worried about with atomic mode setting is handling
>> the legacy case properly.  We'll still need to handle apps that want to
>> change one CRTC at a time without altering the state of other CRTCs.
>
> Fortunately that's not true, you can flag-day it (per drm device even,
> if we want).  If the first thing userspace asks for is atomic modeset
> then you simply disallow subsequent non-atomic modesets, and the
> reverse.  Userspace code will need to grow atomic support anyway, so can
> simply treat -EINVAL from trying it as meaning "no kernel support,
> revert to the older thing".
>
> This does mean you have to update all of userspace to do the new call
> instead of the old one, but that's fine, there's only a handful of
> clients for this API.
>

You'll also need to handles cases like render nodes where we split
resources for multi-seat on one gpu.

Dave.