The Linux community's on-again, off-again relationship with Nvidia appears to have soured once more, amid reports that the GPU maker is back to its old tricks – and worse – when it comes to open source hardware drivers.

Nvidia does release Linux drivers for its graphics cards, but they are proprietary and ship in binary-only format, which is unacceptable for many Linux enthusiasts.

The community's answer has been the Nouveau Project, which aims to create free software drivers for Nvidia cards complete with support for hardware acceleration. For a while, it looked as though the Nouveau developers were keeping up with the pace of Nvidia product releases, but they've run into a new roadblock with Nvidia's latest line, the GeForce GTX 900 series.

The problem, as Phoronix reports, is that Nvidia requires the firmware images for GTX 900 cards to be digitally signed. Allegedly this is to prevent grey market dealers from flashing modified firmware onto cheap graphics cards with low-end GPUs, then passing them off as the high-end versions. But the Nouveau developers think Nvidia's countermeasures go way overboard.

Previous versions of the Nouveau drivers have used clever tricks to generate a compatible version of the GPU firmware and upload it to the card, but that's not possible now that any firmware images must be signed.

"I spent a lot of time trying to find a viable way of doing [GPU context switching] without signed firmware," Nouveau dev Ben Skeggs wrote in a recent code commit, "but the 'security' restrictions on the [Falcon processors] are excessive and go beyond what'd be necessary to protect the host from malicious firmware. This newer [Nvidia hardware] is VERY open-source unfriendly."

Nvidia has reportedly said that it would provide signed firmware images specifically for use in the Nouveau drivers, but so far that hasn't happened. Nvidia has yet to respond to The Reg's request for comment on the matter.

This is hardly the first time Nvidia and the free software community have butted heads, though. Back in 2012, no less than Linus Torvalds himself described the GPU maker as "one of the worst trouble spots we have had with hardware manufacturers."

Nor is the firm's obstinacy limited to the Linux world. The proprietary GTX 900M drivers for Windows also removed some features that allowed users to overclock their GPUs, until gamer outrage caused Nvidia to reverse its decision.

AMD graphics cards, meanwhile, still rely on proprietary firmware images, but the company has been releasing them on a timely basis. And Intel actually provides free software drivers for its HD Graphics chips, although their performance doesn't always match that of the proprietary drivers for Windows. ®