How DRM differs from KGI?

How DRM differs from KGI?

[PRASANNA KUMAR]

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I came across something called as KGI - kernel graphics interface (http://www.kgi-project.org/). It seems it provides the same features as KMS. What is the difference between those two? Any specific reason for not choosing KGI? I don't know much about KGI so feel free to correct me if I am wrong. I think this is the correct mailing list if not just direct me to the proper mailing list.

Thanks,
PrasannaKumar Muralidharan

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Re: How DRM differs from KGI?

[Jerome Glisse]

On Thu, Jun 23, 2011 at 1:34 PM, PRASANNA KUMAR
<prasanna_tsm_kumar@yahoo.co.in> wrote:
> I came across something called as KGI - kernel graphics interface
> (http://www.kgi-project.org/). It seems it provides the same features as
> KMS. What is the difference between those two? Any specific reason for not
> choosing KGI? I don't know much about KGI so feel free to correct me if I am
> wrong. I think this is the correct mailing list if not just direct me to the
> proper mailing list.
> Thanks,
> PrasannaKumar Muralidharan
>

Difference is that KGI try to do more than modesetting (some kind of
acceleration too) and i don't think they ever try to work with the
community (drm/dri/mesa) which is where pretty much all GPU driver dev
are.

Cheers,
Jerome

Re: How DRM differs from KGI?

[olafBuddenhagen]

Hi,

On Fri, Jun 24, 2011 at 09:32:24AM -0400, Jerome Glisse wrote:

> Difference is that KGI try to do more than modesetting (some kind of
> acceleration too)

That's not different from DRM really... Once DRM grew KMS, it did in
fact become *very* similar to KGI.

(The actual graphics driver part of KGI that is... Obviously not the
other mostly unrelated stuff they tried to push along the way.)

> and i don't think they ever try to work with the community
> (drm/dri/mesa) which is where pretty much all GPU driver dev are.

Well, GGI/KGI actually predates DRI/DRM by several years. The fact that
DRI ever came up in the first place is pretty much an attestation of
GGI's failure to get support from the relevant parties.

You are probably right though about failure to cooperate with MESA
developers -- along with the failure to cooperate with XFree86 and Linux
developers...

-antrik-

Re: How DRM differs from KGI?

[olafBuddenhagen]

Hi,

On Thu, Jun 23, 2011 at 11:04:30PM +0530, PRASANNA KUMAR wrote:

> I came across something called as KGI - kernel graphics interface
> (http://www.kgi-project.org/). It seems it provides the same features
> as KMS. What is the difference between those two?

Well, KMS is actually an extension of the DRM; together they handle all
aspects of the graphics hardware access -- which is indeed very similar
to what KGI intended to do. (And it's kinda fun watching KMS developers
reinvent various ideas that were already present in KGI one by one :-) )

> Any specific reason for not choosing KGI?

Several. Generally speaking, KGI did too much. Rather than just graphics
hardware drivers, they also reinvented the whole input and console
systems along the way -- not as patches against the existing code base,
but as a completely new code base written from scratch. Obviously, Linus
didn't like that.

On the application side, they weren't very cooperative either: XGGI (X
server adapted to work with KGI) was basically a fork of XFree86, and
for all I know they never even *tried* discussing the ideas with
upstream. Also their drivers were written from scratch (with some major
overengineering applied there) -- unlike the KMS drivers, which are
somewhat adopted ports of the preexisting and usually quite mature X
drivers.

To sum up, the KGI folks mostly had the right ideas more than a decade
earlier -- but they totally failed to present them in a viable form :-(

-antrik-

Re: How DRM differs from KGI?

[Alan Cox]

> To sum up, the KGI folks mostly had the right ideas more than a decade
> earlier -- but they totally failed to present them in a viable form :-(

Bit more complex IMHO

In the KGI era graphics cards didn't really use main memory much, didn't
have long DMA engine command queues and that made a lot of the
kernel/user transitions very expensive.