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Date:   Mon, 3 May 2021 20:28:11 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Jason Gunthorpe <jgg@ziepe.ca>
Cc:     Logan Gunthorpe <logang@deltatee.com>,
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        Stephen Bates <sbates@raithlin.com>,
        Christoph Hellwig <hch@lst.de>,
        Dan Williams <dan.j.williams@intel.com>,
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        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>,
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        Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH 05/16] dma-mapping: Introduce dma_map_sg_p2pdma()
Message-ID: <20210503182811.GC17174@lst.de>
References: <20210408170123.8788-1-logang@deltatee.com> <20210408170123.8788-6-logang@deltatee.com> <20210427193157.GQ2047089@ziepe.ca> <3c9ba6df-750a-3847-f1fc-8e41f533d1a2@deltatee.com> <20210427230113.GV2047089@ziepe.ca>
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On Tue, Apr 27, 2021 at 08:01:13PM -0300, Jason Gunthorpe wrote:
> 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.

We already have a mapping function that can return errors:
dma_map_sgtable.

I think it might make more sense to piggy back on that, as the sg_table
abstraction is pretty useful basically everywhere that we deal with
scatterlists anyway.

In the hopefully no too long run I plan to get rid of scatterlists in
at least NVMe and other high performance devices anyway.