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

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Date:   Thu, 6 Dec 2018 16:35:12 +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()

Hi Robin,

On Wed, Dec 05, 2018 at 05:17:54PM +0000, Robin Murphy wrote:
> FWIW, this check (and its ACPI equivalent in patch #3) is specifically
> asking "has .add_device() already been called?", rather than the more
> general "is this device managed by an IOMMU?" (to which the exact answer at
> this point is "yes, provided we return successfully from here").
> 
> I have no objection to the change as-is - especially if that usage is within
> the intended scope of this API - I just wanted to call it out in case you're
> also planning to introduce something else which would be even more
> appropriate for that.

Yes, the purpose of the device_iommu_mapped() functions is to check
whether the device has been initialized by the IOMMU driver that handles
it, if any.

So it answers the question: Can I use the device in an IOMMU-API call?
And it is more readable than the dev->iommu_group checks everywhere :)

Regards,

	Joerg