linux-kernel - Re: [PATCH 05/16] dma-mapping: Introduce dma_map_sg

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Date:   Mon, 3 May 2021 12:31:03 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Christoph Hellwig <hch@....de>, Jason Gunthorpe <jgg@...pe.ca>
Cc:     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>,
        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 2021-05-03 12:28 p.m., Christoph Hellwig wrote:
> 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.

Oh, I didn't even realize that existed. I'll use dma_map_sgtable() for v2.

Thanks,

Logan