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Date:   Thu, 30 Mar 2023 12:34:35 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Robin Murphy <robin.murphy@arm.com>
Cc:     Steven Price <steven.price@arm.com>,
        Heiko Stuebner <heiko@sntech.de>,
        Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
        iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org,
        John Keeping <john@metanate.com>
Subject: Re: [PATCH v3] iommu/rockchip: Add missing set_platform_dma_ops
 callback
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On Thu, Mar 30, 2023 at 04:09:03PM +0100, Robin Murphy wrote:

> > +static struct iommu_domain_ops rk_identity_ops = {
> > +	.attach_dev = rk_iommu_identity_attach,
> 
> Since it's going to behave like a regular identity domain and be treated as
> one, it needs to support .free as well.

It would be nice to provide some

static void iommu_domain_static_free(struct iommu_domain *){}

Or adjust the core code so NULL is OK..

I think this pattern of static singleton will be popular. I drafted a
patch for the DART driver like this too

Thanks,
Jason