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From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
	linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-s390@vger.kernel.org, sparclinux@vger.kernel.org,
	iommu@lists.linux-foundation.org, linux-parisc@vger.kernel.org,
	xen-devel@lists.xenproject.org, Christoph Hellwig <hch@lst.de>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Stephen Bates <sbates@raithlin.com>,
	Martin Oliveira <martin.oliveira@eideticom.com>
Subject: Re: [PATCH v1 00/16] .map_sg() error cleanup
Date: Thu, 15 Jul 2021 17:53:09 +0100	[thread overview]
Message-ID: <20210715165309.GO22278@shell.armlinux.org.uk> (raw)
In-Reply-To: <20210715164544.6827-1-logang@deltatee.com>

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?

From what I see in Linus' current tree, we still have cases today
where the return value of dma_map_sg() is compared with zero to
detect failure, so I think that needs fixing before we start changing
the dma_map_sg() implementation to return negative numbers.

I also notice that there are various places that don't check the
return value - and returning a negative number instead of zero may
well cause random other bits to be set in fields.

So, I think there's a fair amount of work to do in all the drivers
before this change can be considered.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

  parent reply	other threads:[~2021-07-15 16:53 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-15 16:45 Logan Gunthorpe
2021-07-15 16:45 ` [PATCH v1 01/16] dma-mapping: Allow map_sg() ops to return negative error codes Logan Gunthorpe
2021-07-16  6:29   ` Christoph Hellwig
2021-07-15 16:45 ` [PATCH v1 02/16] dma-direct: Return appropriate error code from dma_direct_map_sg() Logan Gunthorpe
2021-07-15 16:45 ` [PATCH v1 03/16] iommu: Return full error code from iommu_map_sg[_atomic]() Logan Gunthorpe
2021-07-15 16:45 ` [PATCH v1 04/16] dma-iommu: Return error code from iommu_dma_map_sg() Logan Gunthorpe
2021-07-16  6:31   ` Christoph Hellwig
2021-07-15 16:45 ` [PATCH v1 05/16] alpha: return error code from alpha_pci_map_sg() Logan Gunthorpe
2021-07-15 16:45 ` [PATCH v1 06/16] ARM/dma-mapping: return error code from .map_sg() ops Logan Gunthorpe
2021-07-15 16:45 ` [PATCH v1 07/16] ia64/sba_iommu: return error code from sba_map_sg_attrs() Logan Gunthorpe
2021-07-15 16:45 ` [PATCH v1 08/16] MIPS/jazzdma: return error code from jazz_dma_map_sg() Logan Gunthorpe
2021-07-15 16:45 ` [PATCH v1 09/16] powerpc/iommu: return error code from .map_sg() ops Logan Gunthorpe
2021-07-15 16:45 ` [PATCH v1 10/16] s390/pci: return error code from s390_dma_map_sg() Logan Gunthorpe
2021-07-16  8:24   ` Niklas Schnelle
2021-07-15 16:45 ` [PATCH v1 11/16] sparc/iommu: return error codes from .map_sg() ops Logan Gunthorpe
2021-07-15 16:45 ` [PATCH v1 12/16] parisc: return error code " Logan Gunthorpe
2021-07-15 16:45 ` [PATCH v1 13/16] xen: swiotlb: return error code from xen_swiotlb_map_sg() Logan Gunthorpe
2021-07-19 20:22   ` Boris Ostrovsky
2021-07-15 16:45 ` [PATCH v1 14/16] x86/amd_gart: return error code from gart_map_sg() Logan Gunthorpe
2021-07-16  6:32   ` Christoph Hellwig
2021-07-16 12:11     ` Robin Murphy
2021-07-15 16:45 ` [PATCH v1 15/16] dma-mapping: return error code from dma_dummy_map_sg() Logan Gunthorpe
2021-07-15 16:45 ` [PATCH v1 16/16] dma-mapping: Disallow .map_sg operations from returning zero on error Logan Gunthorpe
2021-07-16  6:33   ` Christoph Hellwig
2021-07-16 12:19     ` Robin Murphy
2021-07-16 16:17     ` Logan Gunthorpe
2021-07-15 16:53 ` Russell King (Oracle) [this message]
2021-07-15 16:56   ` [PATCH v1 00/16] .map_sg() error cleanup Logan Gunthorpe

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