Future desktop on dumb frame buffers?

Ondrej Zary linux at rainbow-software.org
Mon Mar 21 14:13:44 PDT 2011

On Monday 21 March 2011 20:34:38 Corbin Simpson wrote:
> On Mon, Mar 21, 2011 at 12:25 PM, Jesse Barnes <jbarnes at virtuousgeek.org> 
> > On Mon, 21 Mar 2011 19:19:43 +0000
> >
> > timofonic timofonic <timofonic at gmail.com> wrote:
> >> So if KMS is so cool and provides many advantages over fbdev and
> >> such... Why isn't more widely used intead of still relying on fbdev?
> >> Why still using fbdev emulation (that is partial and somewhat broken,
> >> it seems) instead using KMS directly?
> >
> > Used by what?  All three major GPU device classes have KMS support
> > (Intel, ATI, and nVidia).  If you want it for a particular device, you
> > can always port it over.
> >
> > As for fbdev emulation, what's still using it?  There's nothing
> > stopping projects from converting over; X and Wayland can already
> > handle KMS APIs just fine.
> >
> >> I know the graphic driver situation is quite bad on Linux, especially
> >> on the embedded world. Fbdev seems is still quite used there by binary
> >> blob drivers.
> >
> > Probably for a couple of reasons:
> >  1) inertia: fbdev has been around a lot longer, and provides most of
> >  what embedded devices need anyway
> >  2) feature set: why bother doing a full KMS driver if you're not
> >  going to use any of the additional features it would provide (output
> >  management, memory management, execution management)
> Related: We are still missing basic userspace tools (kmsset, e.g.),
> some kind of direct KMS console (kmscon would work, if it existed),
> and an xf86-video-modesetting which compiles and works (this is
> actually possible now, with some patches that landed in 2.6.38 for
> generic KMS access.)

This looks interesting. If existing *fb drivers could be easily converted to 
KMS (including 2D acceleration) and then used in X with a common driver, it 
would be great. Let's say, convert cyber2000fb driver to KMS and use it in X 
with 2D acceleration.

> This is important to me, as the various old drivers I've been hacking
> on won't be accepted upstream without some sort of userspace which can
> work with them. One of the big goals of KMS was a generic
> userspace-facing API, like FB, but without the suck.

Ondrej Zary

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