linux-kernel - Re: [PATCH 2/6] iommu/amd: Implement DOMAIN_ATTR

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Date:	Fri, 27 Jan 2012 09:08:44 +0200
From:	Ohad Ben-Cohen <ohad@...ery.com>
To:	Joerg Roedel <joerg.roedel@....com>
Cc:	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	David Woodhouse <dwmw2@...radead.org>,
	David Brown <davidb@...eaurora.org>,
	Tony Lindgren <tony@...mide.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Stuart Yoder <b08248@...il.com>,
	Scott Wood <scottwood@...escale.com>,
	Hiroshi Doyu <hdoyu@...dia.com>
Subject: Re: [PATCH 2/6] iommu/amd: Implement DOMAIN_ATTR_GEOMETRY attribute

Hi Joerg,

On Thu, Jan 26, 2012 at 8:40 PM, Joerg Roedel <joerg.roedel@....com> wrote:
> Implement the attribute itself and add the code for the
> AMD IOMMU driver.

It's somewhat non-intuitive to have the generic attribute code bundled
with the AMD implementation in the same patch (took me some time to
find it here :).

Maybe split this to two patches ?

> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index ef54718..3d0b0bf 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -345,10 +345,23 @@ EXPORT_SYMBOL_GPL(iommu_device_group);
>  int iommu_domain_get_attr(struct iommu_domain *domain,
>                          enum iommu_attr attr, void *data)
>  {
> -       if (!domain->ops->domain_get_attr)
> -               return -EINVAL;
> +       struct iommu_domain_geometry *geometry;
> +       int ret = 0;
> +
> +       switch (attr) {
> +       case DOMAIN_ATTR_GEOMETRY:
> +               geometry  = data;
> +               *geometry = domain->geometry;

This is not type-safe and will surely bite someone some day.

Sure, we can't have type safety in a multi-purpose generic interface,
but I wonder whether this is the right interface for getting the
geometry ? I.e. why not have a dedicated API for this ?

Thanks,
Ohad.
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