[PATCH v2 2/5] dma-mapping: Introduce dma_iommu_detach_device() API

[Christoph Hellwig]

On Wed, Apr 25, 2018 at 12:10:48PM +0200, Thierry Reding wrote:
> From: Thierry Reding <treding at nvidia.com>
> 
> The dma_iommu_detach_device() API can be used by drivers to forcibly
> detach a device from an IOMMU that architecture code might have attached
> to. This is useful for drivers that need explicit control over the IOMMU
> using the IOMMU API directly.

Given that no one else implements it making it a generic API seems
rather confusing.  For now I'd rename it to
arm_dma_iommu_detach_device() and only implement it in arm.

Once I've got the dma mapping implementations consolidated to a small
enough number we could think about something like a device quirk that
tells the architecture to simply never even attach the iommu dma ops
to start with.