KMS issues: Lack of direct kms console, basic userspace tools like kmsset and docs

[timofonic]

Hello.

I'm not sure if this is the correct section for the message, sorry if not. Tons of sections, but not sure where to put this thread.

As always happens in my, I accidentally made start a quite interesting discussion about KMS.

http://lists.freedesktop.org/archive...ch/009524.html
http://lists.freedesktop.org/archive...ch/000838.html

I wrote the following, maybe others may think I exaggerated but that's how I see it.

> 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.

Jesse Barnes from the Intel Open Source Technology Center replied this...

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)

Then Corbin Simpson (aka MostAwesomeDude, he frequents Phoronix site) replied this...

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 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.

Jesse from Intel replied again...

Yeah, we used to call that drmcon, and it's still a big open. I think
there are some projects that sit on top of fbdev and provide a good
text console with fancy character and input support, but I don't know
if any of them have been ported to KMS to handle multiple outputs or
with an aim toward integrating into a distro as a VT replacement.

kmsset or something would be pretty easy to do; the modetest program in
the drm repo would be a good starting point for that. One limitation
there is handling fbcon, which makes reallocation of the framebuffer
somewhat difficult.

IIRC plymouth or whatever Fedora is using these days uses the KMS APIs
though...

Then other person replied too...

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.

The party not ended, this time Alan Cox provided a very short but interesting reply...

> 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)

3) its got documentation

Then Matt Tuner replied this to him...

My summer of code project's purpose was to create something of a
tutorial for writing a KMS driver. The code, split out into something
like 15 step-by-step patches, and accompanying documentation are
available from Google's website.

http://code.google.com/p/google-summ..._Turner.tar.gz

My repository (doesn't include the documentation) is available here:
http://git.kernel.org/?p=linux/kerne....git;a=summary

There's a 'rebased' branch that contains API changes required for the
code to work with 2.6.37~.

It's nothing fantastic, but I've had a number of people tell me that
it was useful for them.

Thanks,
Matt

So could anyone ellaborate a bit on this? It can be a great article for the Phoronix site.

I hope KMS gets more developer powered, it has lots of potential in different areas. Even it can help to solve the mess of Linux in the embedded sector.

What do you all think?

[yoshi314]

it's certainly very interesting read.

i was also wondering why there is no kms acceleration. good to know that there are other people aware of the problem.