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Message-ID: <20210503182811.GC17174@lst.de>
Date: Mon, 3 May 2021 20:28:11 +0200
From: Christoph Hellwig <hch@....de>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: Logan Gunthorpe <logang@...tatee.com>,
linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
linux-block@...r.kernel.org, linux-pci@...r.kernel.org,
linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
Stephen Bates <sbates@...thlin.com>,
Christoph Hellwig <hch@....de>,
Dan Williams <dan.j.williams@...el.com>,
Christian König <christian.koenig@....com>,
John Hubbard <jhubbard@...dia.com>,
Don Dutile <ddutile@...hat.com>,
Matthew Wilcox <willy@...radead.org>,
Daniel Vetter <daniel.vetter@...ll.ch>,
Jakowski Andrzej <andrzej.jakowski@...el.com>,
Minturn Dave B <dave.b.minturn@...el.com>,
Jason Ekstrand <jason@...kstrand.net>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Xiong Jianxin <jianxin.xiong@...el.com>,
Bjorn Helgaas <helgaas@...nel.org>,
Ira Weiny <ira.weiny@...el.com>,
Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH 05/16] dma-mapping: Introduce dma_map_sg_p2pdma()
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.
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