Raspberry Pi marks 2nd birthday with plan for open source graphics driver

The Raspberry Pi Foundation, with help from chipmaker Broadcom, is laying out a path toward an open source graphics driver for the tiny computer.

Broadcom today "announced the release of full documentation for the VideoCore IV graphics core, and a complete source release of the graphics stack under a 3-clause BSD license," Raspberry Pi creator Eben Upton wrote in a blog post.

Documentation and drivers are available here.

The VideoCore IV GPU is the same as the one used on the Pi. Complicating matters slightly is that Broadcom's "source release targets the BCM21553 cellphone chip," instead of the BCM2835 system-on-chip used on the Pi.

Still, "it should be reasonably straightforward to port this to the BCM2835, allowing access to the graphics core without using the blob," Upton wrote.

That "blob" is the closed source driver code that the Pi requires today. "In common with every other mobile graphics core, using the VideoCore IV 3D graphics core on the Pi requires a block of closed-source binary driver code (a 'blob') which talks to the hardware," Upton wrote. "Our existing open-source graphics drivers are a thin shim running on the ARM11, which talks to that blob via a communication driver in the Linux kernel. The lack of true open-source graphics drivers and documentation is widely acknowledged to be a significant problem for Linux on ARM, as it prevents users from fixing driver bugs, adding features and generally understanding what their hardware is doing."

The Raspberry Pi Foundation is asking its community to port the newly released code to the Pi and is offering a cash reward to whoever can do it first.

"As an incentive to do this work, we will pay a bounty of $10,000 to the first person to demonstrate to us satisfactorily that they can successfully run Quake III at a playable framerate on Raspberry Pi using these drivers," Upton wrote. "This competition is open worldwide, and you can find competition rules here."

Upton further noted that "there are still significant parts of the multimedia hardware on BCM2835 which are only accessible via the blob. But we’re incredibly proud that VideoCore IV is the first publicly documented mobile graphics core and hope this is the first step towards a blob-free future for Raspberry Pi: we're continuing to work on that, and we hope you'll come along with us!"

Upton is also an employee of Broadcom. In an interview with Ars, he noted that he was speaking only for the Raspberry Pi Foundation. However, he authored the Broadcom announcement blog post as well.

In that post, he noted that the source code and documentation release "provides the mobile developer community with the chance to do their own tinkering and upgrade their existing 3G mobile devices with newer generations of the Android operating system."

What's next for the Pi

The Raspberry Pi is now just about two years old, having gone on sale Feb. 29, 2012. 100,000 were sold on its first day, with that number now passing more than 2.5 million.

Upton said the foundation is "a year or two away from thinking about" building new hardware. "We're still seeing really good performance gains on the Pi from attention to detail on the software side," he told Ars. "I think we're some distance from getting to the point where we've tapped out the benefits that are available to us."

Unlike the Arduino and BeagleBone computers, Raspberry Pi isn't an open hardware platform, because its hardware design files aren't freely available. Arduino co-creator Massimo Banzi has noted that "people can prototype on the BeagleBone or the Arduino, and if they decide to make a product out of it, they can go and buy the processors and use our design as a starting point and make their own product out of it."

That isn't possible with the Pi, but that's by design. "Raspberry Pi is not open hardware, and there is no plan currently to release the board design," Upton told Ars. "While we're supportive of the open hardware movement, we don't believe that releasing designs for very high-technology, hard-to-manufacture products like the Pi brings significant direct benefits to end users. Additionally, enabling Raspberry Pi clones would undermine our ability to generate the revenue which, as a not-for-profit, we currently spend on subsidizing FOSS software development and educational material." The foundation has contributed money to open source projects like XBMC, PyPy, Wayland, Scratch, WebKit, and others.

Having "openly documented graphics hardware" for the Pi is a big step for the platform, however, Upton said. What hobbyist computers have in common today is that "if you want to use their multimedia functionality, you have to use closed source software," he said. "More openness in mobile graphics is a good thing."