linux-kernel - Re: [PATCH v1 00/16] .map

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Date:   Thu, 15 Jul 2021 10:56:09 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     linux-kernel@...r.kernel.org, linux-alpha@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, sparclinux@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-parisc@...r.kernel.org,
        xen-devel@...ts.xenproject.org, Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Stephen Bates <sbates@...thlin.com>,
        Martin Oliveira <martin.oliveira@...eticom.com>
Subject: Re: [PATCH v1 00/16] .map_sg() error cleanup




On 2021-07-15 10:53 a.m., Russell King (Oracle) wrote:
> On Thu, Jul 15, 2021 at 10:45:28AM -0600, Logan Gunthorpe wrote:
>> Hi,
>>
>> This series is spun out and expanded from my work to add P2PDMA support
>> to DMA map operations[1].
>>
>> The P2PDMA work requires distinguishing different error conditions in
>> a map_sg operation. dma_map_sgtable() already allows for returning an
>> error code (where as dma_map_sg() is only allowed to return zero)
>> however, it currently only returns -EINVAL when a .map_sg() call returns
>> zero.
>>
>> This series cleans up all .map_sg() implementations to return appropriate
>> error codes. After the cleanup, dma_map_sg() will still return zero,
>> however dma_map_sgtable() will pass the error code from the .map_sg()
>> call. Thanks go to Martn Oliveira for doing a lot of the cleanup of the
>> obscure implementations.
>>
>> The patch set is based off of v5.14-rc1 and a git repo can be found
>> here:
> 
> Have all the callers for dma_map_sg() been updated to check for error
> codes? If not, isn't that a pre-requisit to this patch set?

No. Perhaps I wasn't clear enough: This series is changing only
impelemntations of .map_sg(). It does *not* change the return code of
dma_map_sg(). dma_map_sg() will continue to return zero on error for the
foreseeable future. The dma_map_sgtable() call already allows returning
error codes and it will pass the new error code through. This is what
will be used in the P2PDMA work.

Logan