Old AMD Radeon graphics cards are getting another quality-of-life upgrade on Linux, courtesy of Valve. Timur Kristóf, a member of Valve's open-source graphics driver team, has posted a patch series adding DRM format modifier support to GFX6 through GFX8 hardware, spanning the original GCN 1.0 cards through the Polaris and Fiji generations. Until now, this was the only family of GPUs supported by the AMDGPU kernel driver without modifier support.
DRM format modifiers describe how image buffers are tiled, compressed, and otherwise laid out in memory. Without them, modern Linux compositors and userspace stacks have to either fall back to slower paths or skip certain features entirely on older hardware. On GFX6-8, the graphics block can only use a fixed set of tiling modes programmed by the kernel from a tiling mode table, and the new modifiers encode exactly the information needed to describe those layouts to userspace.
The practical upshot is broader interoperability across the Linux graphics stack on cards that go back to the Radeon HD 7000 series. Vulkan-based Wayland compositors, compositors running on top of the Zink OpenGL-on-Vulkan layer, and cross-API workflows like VAAPI to OpenGL to Vulkan handoffs should all start working properly on this hardware. It is the kind of plumbing that mostly goes unnoticed when it works and quietly breaks features when it doesn't.
Kristóf has been on a streak of GCN 1.0/1.1 era improvements lately, including migrating those older GPUs from the legacy Radeon driver to the modern AMDGPU driver and improving display handling on older APUs. The kernel-side work is paired with a corresponding Mesa merge request that wires the same modifier support into the RADV Vulkan driver and the RadeonSI OpenGL driver in userspace.