1. Computers
  2. Display Drivers
  3. Graphics Cards
  4. Memory
  5. Motherboards
  6. Processors
  7. Software
  8. Storage
  9. Operating Systems


Facebook RSS Twitter Twitter Google Plus


Phoronix Test Suite

OpenBenchmarking.org

Mixed Feelings Over The PSCNV Nouveau Driver Fork

Nouveau

Published on 30 October 2010 09:35 AM EDT
Written by Michael Larabel in Nouveau
8 Comments

Three days ago we passed along the latest information on the PSCNV driver, which is a fork of the open-source Nouveau driver for NVIDIA graphics cards, with this information coming from Christopher Bergström of PathScale. As this was one of our first articles talking about the PSCNV driver at length, many readers were surprised by this fork with the upstream Nouveau driver still lacking even an official release. Some feel that this fork is a bad idea (it's even been compared to the dead RadeonHD driver) while others are in support of PathScale's efforts. Since publishing that article we have learned a few more details on the PSCNV driver from some of its developers within our forums.

For those that had not read our prior article on the PSCNV driver, it's a fork largely of Nouveau's kernel DRM driver. The company PathScale had forked the open-source DRM code so that they could gut TTM out of the driver and replace it with their own solution. TTM is the kernel memory manager within the mainline Linux kernel for GPUs (along with Intel's Graphics Execution Manager) that is used not only by Nouveau but also the Radeon and VMware drivers, among others. PathScale wanted to rid the Nouveau driver of GEM+TTM since in its current form is incompatible with OpenCL/CUDA and other GPGPU technologies due to it freely moving around buffers without notice. They also don't like TTM since it's more difficult to port to other non-Linux operating systems, among other reasons.

Unlike the upstream Nouveau driver that focuses upon providing some level of support for all NVIDIA GPUs, PSCNV only focuses upon the NV50 ASICs and later that are GPGPU-capable.

This PSCNV driver fork has been going on for several months already and they have already brought up 2D support for the NVIDIA GeForce GTX 400 "Fermi" series graphics cards. Those working on this open-source NVIDIA driver have also been extending the pool of documentation for NVIDIA hardware they have assembled through reverse-engineering.

For those wondering about PathScale's motives with working on an open-source Linux graphics driver -- seeing as they are a company specializing in proprietary compiler development for x86_64 clusters -- they are primarily interested in exploiting the compute capabilities (i.e. OpenCL) of the NVIDIA GeForce/Quadro hardware.

Martin Peres, who is involved with both the PSCNV and Nouveau drivers, has said that the PSCNV work is mostly a fork of the kernel code. We have seen a xf86-video-pscnv DDX driver on PathScale's GitHub, but Martin says it's mostly untouched and there really is just a one-line patch separating the two. That patch should eventually make its way back into the upstream xf86-video-nouveau X.Org driver. We will hopefully not see forked Gallium3D drivers for NVIDIA hardware. As far as any concerns go about the PathScale driver not being open-source friendly, Martin has said, "The kernel driver, libdrm and the (very slightly modified) ddx are and will stay open source. As for mesa, they are working upstream as they have commit access."

From Martin's comment, PathScale is not only interested in GPGPU on NVIDIA cards, but to increase performance. In another comment, we learned the creator of the NV50 Gallium3D driver is also working on the Fermi Gallium3D driver and he has been hired by PathScale for their project. Another comment from Peres: "We hope pscnv and nouveau will merge someday, but pscnv needs to experiment first" and at the same time "we are far from the merging point."

In terms of merging the PSCNV kernel code back into the Nouveau DRM, Bergström had commented that a few of the main Nouveau developers would need to be willing to let TTM get re-factored out, it would be a technical challenge to merge back the code as the two code-bases have already diverged quite a bit, and the graphics support for NV50 GPUs and earlier hardware would need to be improved.

About the comment made in the earlier PSCNV article about OpenGL 4.0 support being looked at for potentially next year, Christopher Bergström elaborated on it, "The OpenGL4 comment was only a personal one. I would really love to see a community of developers make a todo list, plan and try to tackle this. I think within a year's time if it's broken down into small manageable pieces with good docs it can be done."

Read this thread for the full discussion concerning the compute-focused PSCNV driver.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
Latest Linux Hardware Reviews
  1. A Walkthrough Of The New 32 System Open-Source Linux Benchmarking Test Farm
  2. Habey MITX-6771: Mini-ITX Board With Quad-Core J1900 Bay Trail
  3. OCZ Vector 150 SSD On Linux
  4. Noctua i4 CPU Cooler: Great For Cooling High-End LGA-2011v3 CPUs
Latest Linux Articles
  1. AMD Kaveri: Open-Source Radeon Gallium3D vs. Catalyst 14.12 Omega Driver
  2. 12-Way AMD Catalyst 14.12 vs. NVIDIA 346 Series Linux GPU Comparison
  3. AMD Catalyst 14.12 Omega Driver Brings Mixed Results For Linux Users
  4. 6-Way Winter 2014 Linux Distribution Comparison
Latest Linux News
  1. WTFTW: A Tiling Window Manager Written In Rust
  2. Jolla's Sailfish OS Update 10 Is Now Available
  3. HP To Launch Linux++ Operating System Next Year
  4. Civilization: Beyond Earth Launches For Linux
  5. NIR Has Been Revised As A New IR For Mesa
  6. New 64-bit Linux Kernel Vulnerabilities Disclosed This Week
  7. PostgreSQL 9.4 Brings JSONB & Many Other New Features
  8. That Nasty Linux Kernel Lockup Bug Is Still Unresolved
  9. KDE's Krita Loses Its Main Backer
  10. Inline Data Support Comes To CephFS With Linux 3.19
Latest Forum Discussions
  1. Debian init discussion in Phoenix Wright format
  2. XLennart: A Game For Systemd Haters With Nothing Better To Do
  3. Bench specific mount point
  4. Tool for measuring FPS in games
  5. Need some hand holding with upgrading xserver
  6. Ubuntu Developers Still Thinking What To Do About Adobe Flash Support
  7. Microsoft buying Mojang
  8. Updated and Optimized Ubuntu Free Graphics Drivers