linux-kernel - Re: [PATCH 2/5] iommu/of: Use device_iommu

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Date:   Fri, 7 Dec 2018 10:31:58 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     iommu@...ts.linux-foundation.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joerg Roedel <jroedel@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] iommu/of: Use device_iommu_mapped()

On Thu, Dec 06, 2018 at 05:42:16PM +0000, Robin Murphy wrote:
> For sure - although I am now wondering whether "mapped" is perhaps a little
> ambiguous in the naming, since the answer to "can I use the API" is yes even
> when the device may currently be attached to an identity/passthrough domain
> or blocked completely, neither of which involve any "mapping". Maybe simply
> "device_has_iommu()" would convey the intent better?

The name is shorter version of:

	device_is_behind_an_iommu_remapping_its_dma_transactions()
	:)

The name is not perfect, but device_has_iommu() is not better because it
might be considered as a check whether the device itself has an IOMMU
built-in.

In the end an identity-mapping is also still a mapping (if the iommu
needs a page-table for that is an implementation detail), as is a
mapping with no page-table entries at all (blocking). So I think
device_iommu_mapped() is a reasonable choice.

Regards,

	Joerg