Hello Christian, On Mon, 14 Apr 2025 11:11:48 +0200 Christian König <christian.koe...@amd.com> wrote:
> Maybe I should try to better explain the concern here. The question > is "Where is the source code of your FPGA driver?". > > I mean that you are trying to replace the out-of-tree solution is > rather welcomed, but the out-of-tree solutions are out-of-tree > because they don't fit with requirements to be added to the core > Linux tree. > > And one of those requirements is that you need to provide the source > code of the userspace user of this interface, in this case here that > is your FPGA driver. An MIT/X11 license is usually sufficient, GPL is > of course seen as better and it must not be a toy application, but > rather the real thing. Where is this requirement for UIO? The UIO subsystem does not have such a requirement, unlike indeed some other kernel subsystems such as DRM. But the practical situation is different: for DRM it makes a lot of sense to enforce having open-source code in user-space, as we want to force GPU vendors to open their OpenGL/Vulkan implementations. However, for UIO it makes little sense, because UIO is typically used to control some super-specific FPGA IP blocks that are totally irrelevant outside of the very specific product they are included in. Most likely if those drivers were open-sourced and tried to be upstream they would be rejected because their usefulness in the upstream kernel is basically zero (but they would have an on-going maintenance effort for the whole community). > And that is what people usually don't want and that's why no in-tree > solution exists for this. And that doesn't make sense because UIO already exists, and allows to achieve 95% of what people already need, to the exception of this DMA issue. Thomas -- Thomas Petazzoni, co-owner and CEO, Bootlin Embedded Linux and Kernel engineering and training https://bootlin.com
