Nouveau X.Org Driver Drops GLAMOR Support

[phoronix]

Phoronix: Nouveau X.Org Driver Drops GLAMOR Support

The xf86-video-nouveau DDX driver has dropped support for GLAMOR hardware acceleration and in the process eliminated the support for the Maxwell GPUs...

http://www.phoronix.com/scan.php?page=news_item&px=XOrg-Nouveau-Drop-GLAMOR

[Ericg]

I'm pretty much waiting for the day when -modesetting is the main DDX driver for intel/radeon/nouveau on Xorg. I know its a ways off, lot of work to be done, but it definitely seems to be moving that direction.

[Kemosabe]

I'm pretty much waiting for the day when -modesetting is the main DDX driver for intel/radeon/nouveau on Xorg. I know its a ways off, lot of work to be done, but it definitely seems to be moving that direction.

It's something desirable? Please explain.

[sobkas]

It's something desirable? Please explain.

It will put more pressure on modesetting infrastructure that is used not only by Xorg but also Wayland. That work will not be wasted when X11 will be only used on top of Wayland.

[blackshard]

It will put more pressure on modesetting infrastructure that is used not only by Xorg but also Wayland. That work will not be wasted when X11 will be only used on top of Wayland.

I know nothing about modesetting driver, but reading the news here I could figure that it is a sort of "generic" DRM driver good for all kernel drivers that implement kernel modesetting and have a proper egl/opengl implementation, am I right? I'd like to know more about this driver.

[Guest]

I read a while back that the modesetting driver performed on some AMD cards a bit better than the DDX driver (I think pontostroy had a benchmark or something that showed this).

I recall trying it myself a while back and had some issue wtih it that made me revert; can't recall what happened though (may have been instability); might try it again in the near future.

[RussianNeuroMancer]

For me reason why I doesn't stuck with modesettting is lack of working vsync: https://bugs.freedesktop.org/show_bug.cgi?id=91924

[gigaplex]

If the modesetting driver does everything that the nouveau DDX driver does, what's the point in having the nouveau one?

[boxie]

If the modesetting driver does everything that the nouveau DDX driver does, what's the point in having the nouveau one?

AFAIK - Modesetting + GLAMOR does everything over OpenGL - the nouveau DDX driver has a 2d acceleration path.

There is also different levels of support/readiness/testing in each of the drivers

[SimonK]

I know nothing about modesetting driver, but reading the news here I could figure that it is a sort of "generic" DRM driver good for all kernel drivers that implement kernel modesetting and have a proper egl/opengl implementation, am I right? I'd like to know more about this driver.

There are two separate concepts here: modesetting (KMS) and glamor (rendering X via opengl), where glamor relies on DRM. However the two separate concepts can be combined together well. A DDX driver might set graphics mode by poking card control registers from userspace (oldstyle) or by using the KMS interfaces provided by the card-specific kernel driver. And a DDX driver might render X commands from clients by directly generating card-specific drawing commands, or by generating opengl equivalents and feeding them through the card's opengl library before passing them to the card (glamor).

If a card's kernel driver supports both KMS (modesetting) and DRM (transferring buffers of data from userspace to GPU), _and_ there is a good opengl library for the card, then it is possible to drive it from a _general-purpose_, ie card-independent DDX driver. Or in other words, a single generic kms/glamor-based DDX driver can control _all cards_ which provide proper KMS/DRM/opengl support. Yay, no more card-specific DDX drivers needed!

Of course, there's a catch. Right now, dedicated DDX drivers can perform some X drawing operations faster than can be done by going via OpenGL, ie DDX is faster than glamor for most cards. However glamor is quite new, and improving fast.

And by the way, the "internal" glamor support embedded into some card-specific DDX drivers (intel in particular) is just a temporary measure, for experimental purposes; hopefully soon the standalone glamor driver will mature and the "embedded" glamor support can be removed from those (few) drivers that do it.

This KMS/DRM/OpenGL architecture for an X DDX driver is actually very similar to Wayland.