Re: Future desktop on dumb frame buffers?

On Mon, Mar 21, 2011 at 5:13 PM, Ondrej Zary [off-list ref] wrote:

On Monday 21 March 2011 20:34:38 Corbin Simpson wrote:

quoted

On Mon, Mar 21, 2011 at 12:25 PM, Jesse Barnes [off-list ref]

wrote:

quoted

quoted

On Mon, 21 Mar 2011 19:19:43 +0000

timofonic timofonic [off-list ref] wrote:

quoted

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.

quoted

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.

You'd need to update the existing DDX to work with KMS.  Generally you
need some sort of userspace driver to allocate the buffers, deal with
acceleration alignment, build the acceleration command buffers, and
interface with X.

Alex

quoted

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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