Re: [PATCH v2 05/15] iommu: Add QDA compute context bank bus to iommu_buses

[Jason Gunthorpe]

On Mon, Aug 17, 2026 at 10:17:40AM +0530, Ekansh Gupta wrote:
> Register the QDA compute context bank bus (qda-compute-cb) with the
> IOMMU subsystem by adding it to the iommu_buses[] array.
> 
> The QDA driver creates synthetic devices on this bus to represent
> IOMMU context banks (CBs). Each CB device needs its own IOMMU domain
> so that the DSP memory manager can enforce per-session address space
> isolation. Without this registration, the IOMMU subsystem does not
> probe CB devices for IOMMU groups and of_dma_configure() in the bus
> dma_configure callback has no IOMMU domain to attach to.

I didn't notice a clear explanation of the proposed DT schema for this

But it looks awfully similar to the other driver that was creating a
kernel synthetic bus for actual real HW, that wasn't well liked.

What is this for? Why can't you have a normal DT binding for the
iommu with normal devices?

Jason