Hello Andrew, On Mon, 14 Apr 2025 12:08:44 -0500 Andrew Davis <a...@ti.com> wrote:
> "UIO is a broken legacy mess, so let's add more broken things > to it as broken + broken => still broken, so no harm done", am I > getting that right? Who says UIO is a "broken legacy mess"? Only you says so. I don't see any indication anywhere in the kernel tree suggesting that UIO is considered a broken legacy mess. Keep in mind that when you're running code as root, you can load a kernel module, which can do anything on the system security-wise. So letting UIO expose MMIO registers of devices to userspace applications running as root is not any worse than that. > If your FPGA IP can do DMA then you should not be using UIO in > the first place, see UIO docs: > > > Please note that UIO is not an universal driver interface. Devices that > > are already handled well by other kernel subsystems (like networking or > > serial or USB) are no candidates for an UIO driver. > > The DMA subsystem already handles DMA devices, so write a DMA driver. My FPGA IP block is not a DMA controller that would fit the dmaengine kernel subsystem. It's a weird custom device that doesn't fit in any existing subsystem, and that happens to do "peripheral DMA" (i.e the IP block is DMA-capable itself, without relying on a separate DMA controller). So this (very valid) recommendation from the UIO documentation doesn't apply to my device. Best regards, Thomas -- Thomas Petazzoni, co-owner and CEO, Bootlin Embedded Linux and Kernel engineering and training https://bootlin.com
