Nouveau is a free software graphics driver for Nvidia graphics card. It is not very good and it performs horrible compared to the proprietary non-free binary blog driver from Nvidia. It can be used to get a basic 2D desktop on most not brand new Nvidia graphics cards. Accelerated 3D graphics, video playback and other features you would expect a graphics driver to provide are not and can not be supported.
Current Status 2020
The nouveau developers stated goal for nouveau is to create a
"Reliable Open-Source driver for Nvidia GPUs"
The reason they aim for reliability and not performance is that power management features can't be implemented thanks to Nvidia's firmware restrictions.
Graphics cards from Nvidia require a signed firmware for most functions. It would be possible to dump the firmware from the proprietary Nvidia driver but that would require that everyone who wants to use
nouveau downloads a specific version of Nvidias proprietary drivers and extract the firmware for their card. The firmware and the firmware interfaces change from driver version to driver version so nouveau would have to base their code on a specific driver version if they were to go down that road. The nouveau developers don't want to do that.
Firmware is a problem on older cards too. nouveau can control GPU clock speed on older GeForce 700 series Kepler cards with a reverse engineered firmware but it can not control the fans which means that the graphics cards would overheat after a short period of sustained load at higher clocks.
Fosdem 2020 Presentation
Template:VideoVideo license: Cc-by-sa-2.0, Fosdem 2020
The nouveau driver has some OpenCl code which, as of January 2020, doesn't work. But it's there. And you can try it by setting
Don't expect to be able to actually use any OpenCL software with nouveau just yet. It is more of a thing you can enable and play with if you are interested in improving the Nouveau driver.
nouveau has a NIR backend which can be tested by setting
Good luck with doing that. It's there, you can try it, but don't expect a problem-free experience.
The few paid developers who are working on nouveau are employed by the IBM subsidiary Redhat. They also have an intern who is working on a shader cache.