It is certainly more useful on Pi5 with iommus than on Pi4.
It has uses where you haven't got control of the code that does the allocation, but you want to import it for use as a texture, DRM plane, V4L2 buffer, or other kernel subsystem that supports dmabuf import.
I know my colleague who does most of the wlroots and labwc work had investigated it for use within the compositor as he couldn't guarantee that all resources would be dmabufs, but we wanted to investigate the potential of using the DRM writeback connector to do the composition. We therefore needed a way of pulling the userspace buffers into a dmabuf, and udmabuf provided that.
Discussion in https://github.com/raspberrypi/linux/issues/6706 with Robert Mader from Collabora over the use of it.
It has uses where you haven't got control of the code that does the allocation, but you want to import it for use as a texture, DRM plane, V4L2 buffer, or other kernel subsystem that supports dmabuf import.
I know my colleague who does most of the wlroots and labwc work had investigated it for use within the compositor as he couldn't guarantee that all resources would be dmabufs, but we wanted to investigate the potential of using the DRM writeback connector to do the composition. We therefore needed a way of pulling the userspace buffers into a dmabuf, and udmabuf provided that.
Discussion in https://github.com/raspberrypi/linux/issues/6706 with Robert Mader from Collabora over the use of it.
Statistics: Posted by 6by9 — Tue Jul 08, 2025 3:55 pm