Recent video-related commits: summary wanted

[Gerard Lally]

There have been many video-related commits to the source tree recently,
which I am doing my best to understand. Radeon, nouveau, drm, kms, and
the like. It would be nice if someone would summarise what is happening
and what difference it makes, and whether NetBSD 7 will benefit. A
question I have for starters: do these changes bring native X up to date
in -7, and if so would there be any compelling reason to choose modular
X instead?

[Roy Bixler]

Post by Gerard Lally
There have been many video-related commits to the source tree recently,
which I am doing my best to understand. Radeon, nouveau, drm, kms, and
the like. It would be nice if someone would summarise what is happening
and what difference it makes, and whether NetBSD 7 will benefit. A
question I have for starters: do these changes bring native X up to date
in -7, and if so would there be any compelling reason to choose modular
X instead?

Whether NetBSD 7 benefits is on the eye of the beholder, but I believe
the basic purpose of these commits is to import code from the Linux
Direct Rendering Manager subsystem. This is the part of the kernel
that interfaces with the Graphics Processing Unit of the system. The
idea is to put the system into graphics mode at bootup, eliminating
the classic "text mode". In a sense, text mode still exists from what
I've seen of Linux systems, which generally use the DRM subsystem to
change fonts to different sizes. The X Server's operation becomes
more seamless.

I don't think I've seen the full benefit of this code yet, since the
system I've installed NetBSD 7 on has an NVidia card and it doesn't
seem that Nouveau is active by default. I will be interested to see
how it works. If it's like my expreience in Linux, then it will work
fairly well and actually be more stable than the proprietary NVidia
driver. The disadvantage is that it doesn't support as many NVidia
cards or, for the cards it does support, it may not support all of the
features of those cards. I also found that suspend/resume worked
better with the NVidia driver than with the Nouveau driver.

[Gerard Lally]

Post by Roy Bixler

Post by Gerard Lally
There have been many video-related commits to the source tree recently,
which I am doing my best to understand. Radeon, nouveau, drm, kms, and
the like. It would be nice if someone would summarise what is happening
and what difference it makes, and whether NetBSD 7 will benefit. A
question I have for starters: do these changes bring native X up to date
in -7, and if so would there be any compelling reason to choose modular
X instead?

Whether NetBSD 7 benefits is on the eye of the beholder, but I believe
the basic purpose of these commits is to import code from the Linux
Direct Rendering Manager subsystem. This is the part of the kernel
that interfaces with the Graphics Processing Unit of the system. The
idea is to put the system into graphics mode at bootup, eliminating
the classic "text mode". In a sense, text mode still exists from what
I've seen of Linux systems, which generally use the DRM subsystem to
change fonts to different sizes. The X Server's operation becomes
more seamless.
I don't think I've seen the full benefit of this code yet, since the
system I've installed NetBSD 7 on has an NVidia card and it doesn't
seem that Nouveau is active by default. I will be interested to see
how it works. If it's like my expreience in Linux, then it will work
fairly well and actually be more stable than the proprietary NVidia
driver. The disadvantage is that it doesn't support as many NVidia
cards or, for the cards it does support, it may not support all of the
features of those cards. I also found that suspend/resume worked
better with the NVidia driver than with the Nouveau driver.

Thanks for the information Roy. I'm probably slow to understand this but
is this DRM a supplement to the {nvidia,nouveau,radeon} driver or a
replacement for it? It seems to me from what you say in the first
paragraph its scope is quite narrow, affecting only bootup, but then in
your second paragraph it seems to be a replacement for the driver - you
hope it is "more stable than the proprietary NVidia driver".

[Patrick Welche]

Post by Gerard Lally
Thanks for the information Roy. I'm probably slow to understand this but
is this DRM a supplement to the {nvidia,nouveau,radeon} driver or a
replacement for it?

I see it rather as DRM/KMS (I'm not acronym compliant) is a necessary
prerequisite for "new" intel, etc., drivers to work.

Cheers,

Patrick

[Roy Bixler]

Post by Patrick Welche

Post by Gerard Lally
Thanks for the information Roy. I'm probably slow to understand this but
is this DRM a supplement to the {nvidia,nouveau,radeon} driver or a
replacement for it?

I see it rather as DRM/KMS (I'm not acronym compliant) is a necessary
prerequisite for "new" intel, etc., drivers to work.

That's my understanding as well and it makes sense. After all, if the
kernel defines its own interface for graphics functionality, then
other graphics-related software like the X Server would want to use
it if only to interact better with the kernel.

I am kind of curious about the Nouveau vs. NVidia drivers. Both
target NVidia GPUs and Nouveau was started as a reverse-engineering
effort due to NVidia driver licensing issues. On one of my systems,
I'm using the NVidia X server under NetBSD 6 and 7 without any real
problems. I've also had fairly good luck with the Nouveau driver
under Linux on the same hardware. Does anyone have any idea which
direction NetBSD 7 will take regarding NVidia graphics drivers?

[Jan Danielsson]

Post by Gerard Lally
There have been many video-related commits to the source tree recently,
which I am doing my best to understand. Radeon, nouveau, drm, kms, and
the like. It would be nice if someone would summarise what is happening
and what difference it makes,

In a strict practical sense..

I bought a graphics card for my NetBSD system a few years back which
is no longer available in stores (since long ago). When I mentioned
this card on IRC a while back someone said "That's the last ATI chip
you'll get working with accelerated graphics in NetBSD until DRM/KMS is
supported.".

Essentially, not having DRM/KMS sets a date which more or less says
"chips released after this date won't work in xorg on your system,
because all the new drivers use DRM/KMS.".

Getting DRM/KMS won't magically make all chips available to NetBSD,
but it'll allow more (and more importantly: somewhat recent) graphics
cards to be used with acceleration.

In short: Assume that "all" new xorg drivers use DRM/KMS.