IOMMU vs Scatter Gather

Posted May 21, 2025 15:57 UTC (Wed) by andy_shev (subscriber, #75870)
In reply to: IOMMU vs Scatter Gather by leon
Parent article: A new DMA-mapping API

How would it affect the DMA engine drivers (drivers/dma/)? They are mostly if not all use SG lists to perform DMA linked link transactions. And it's not related to IOMMU (at least directly, AFAIU).

IOMMU vs Scatter Gather

Posted May 22, 2025 6:42 UTC (Thu) by leon (subscriber, #74771) [Link]

Our plan is to change modern systems, which use general dma-iommu.c implementation.
Rest of the DMA engines will keep their implementation as is.

The use of SG isn't prohibited and have a lot of valid use cases. For example, if your code doesn't need to deal
with memory without struct *page, use SG.

The easiest way to see who is the target of this API is to grep sg_alloc_table_from_pages. I didn't look if all of them need to be changed, but from glance look many of them will benefit from this API.

Thanks