Required backwards support level?

[Lauri Kasanen]

On Sun, 6 Apr 2014 10:53:58 -0400
Rob Clark <robdclark at gmail.com> wrote:

> On Sun, Apr 6, 2014 at 8:26 AM, Lauri Kasanen <cand at gmx.com> wrote:
> > Hi,
> >
> > Obviously old userspace + new kernel combo needs to be supported. But
> > I'm not so sure about a mixed case, does old userspace + new userspace
> > need to be supported to run at the same time?
> >
> > For example, a new 64-bit mesa+libdrm and a 32-bit old set, both
> > running apps at the same time.
> >
> > Or is it acceptable to assume that once a new userspace has been run,
> > an old one won't be run for this boot?
> 
> old 32b userspace in a chroot, for example?

Yes, for example.
 
> Maybe you can give a better description of what you are wanting to do?
>  Could you decide on 32b vs 64b userspace on a per 'struct drm_file'
> basis (ie. each time /dev/dri/cardN is opened)?

This is related to my memory management work. As the VRAM queue is
global, it cannot be determined on a per-app basis. If at least one
client is running old userspace, the new scoring cannot be used.

Switching live between the two would bring additional complexity. I'd
hope to be able to determine by the first 3d app if the userspace is
new enough. But that depends on if it's expected to be able to run
mixed loads.

- Lauri