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Date:   Tue, 27 Apr 2021 20:01:13 -0300
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     Logan Gunthorpe <logang@deltatee.com>
Cc:     linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
        linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
        linux-mm@kvack.org, iommu@lists.linux-foundation.org,
        Stephen Bates <sbates@raithlin.com>,
        Christoph Hellwig <hch@lst.de>,
        Dan Williams <dan.j.williams@intel.com>,
        Christian =?utf-8?B?S8O2bmln?= <christian.koenig@amd.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Don Dutile <ddutile@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Jakowski Andrzej <andrzej.jakowski@intel.com>,
        Minturn Dave B <dave.b.minturn@intel.com>,
        Jason Ekstrand <jason@jlekstrand.net>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Xiong Jianxin <jianxin.xiong@intel.com>,
        Bjorn Helgaas <helgaas@kernel.org>,
        Ira Weiny <ira.weiny@intel.com>,
        Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH 05/16] dma-mapping: Introduce dma_map_sg_p2pdma()
Message-ID: <20210427230113.GV2047089@ziepe.ca>
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On Tue, Apr 27, 2021 at 04:55:45PM -0600, Logan Gunthorpe wrote:

> > Also, I see only 8 users of this function. How about just fix them all
> > to support negative returns and use this as the p2p API instead of
> > adding new API?
> 
> Well there might be 8 users of dma_map_sg_attrs() but there are a very
> large number of dma_map_sg(). Seems odd to me to single out the first as
> requiring these changes, but leave the latter.

At a high level I'm OK with it. dma_map_sg_attrs() is the extra
extended version of dma_map_sg(), it already has a different
signature, a different return code is not out of the question.

dma_map_sg() is just the simple easy to use interface that can't do
advanced stuff.

> I'm not that opposed to this. But it will make this series a fair bit
> longer to change the 8 map_sg_attrs() usages.

Yes, but the result seems much nicer to not grow the DMA API further.

Jason