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From: Christoph Hellwig <hch@lst.de>
To: James Hogan <jhogan@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	iommu@lists.linux-foundation.org, sstabellini@kernel.org,
	x86@kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org,
	linux-mips@linux-mips.org, sparclinux@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 11/13] mips,unicore32: swiotlb doesn't need sg->dma_length
Date: Thu, 3 May 2018 05:56:43 +0200	[thread overview]
Message-ID: <20180503035643.GA9781@lst.de> (raw)
In-Reply-To: <20180502222017.GC20766@jamesdev>

On Wed, May 02, 2018 at 11:20:18PM +0100, James Hogan wrote:
> On Wed, Apr 25, 2018 at 07:15:37AM +0200, Christoph Hellwig wrote:
> > Only mips and unicore32 select CONFIG_NEED_SG_DMA_LENGTH when building
> > swiotlb.  swiotlb itself never merges segements and doesn't accesses the
> > dma_length field directly, so drop the dependency.
> 
> Is that at odds with Documentation/DMA-API-HOWTO.txt, which seems to
> suggest arch ports should enable it for IOMMUs?

swiotlb isn't really an iommu..  That being said iommus don't have to
merge segments either if they don't want to, and we have various
implementations that don't.  The whole dma api documentation needs
a major overhaul, including merging the various files and dropping a lot
of dead wood.  It has been on my todo list for a while, with an inner
hope that someone else would do it before me.

  reply	other threads:[~2018-05-03  3:54 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-25  5:15 centralize SWIOTLB config symbol and misc other cleanups V3 Christoph Hellwig
2018-04-25  5:15 ` [PATCH 01/13] iommu-common: move to arch/sparc Christoph Hellwig
2018-04-25 14:58   ` David Miller
2018-04-25  5:15 ` [PATCH 02/13] iommu-helper: unexport iommu_area_alloc Christoph Hellwig
2018-04-25  5:15 ` [PATCH 03/13] iommu-helper: mark iommu_is_span_boundary as inline Christoph Hellwig
2018-04-25  5:15 ` [PATCH 04/13] iommu-helper: move the IOMMU_HELPER config symbol to lib/ Christoph Hellwig
2018-04-25  5:15 ` [PATCH 05/13] scatterlist: move the NEED_SG_DMA_LENGTH config symbol to lib/Kconfig Christoph Hellwig
2018-04-25  5:15 ` [PATCH 06/13] dma-mapping: move the NEED_DMA_MAP_STATE " Christoph Hellwig
2018-04-25  5:15 ` [PATCH 07/13] arch: remove the ARCH_PHYS_ADDR_T_64BIT config symbol Christoph Hellwig
2018-05-02 20:11   ` James Hogan
2018-04-25  5:15 ` [PATCH 08/13] arch: define the ARCH_DMA_ADDR_T_64BIT config symbol in lib/Kconfig Christoph Hellwig
2018-05-02 22:09   ` James Hogan
2018-04-25  5:15 ` [PATCH 09/13] PCI: remove CONFIG_PCI_BUS_ADDR_T_64BIT Christoph Hellwig
2018-04-25  5:15 ` [PATCH 10/13] arm: don't build swiotlb by default Christoph Hellwig
2018-04-25  5:15 ` [PATCH 11/13] mips,unicore32: swiotlb doesn't need sg->dma_length Christoph Hellwig
2018-05-02 22:20   ` James Hogan
2018-05-03  3:56     ` Christoph Hellwig [this message]
2018-05-03  6:47       ` James Hogan
2018-04-25  5:15 ` [PATCH 12/13] swiotlb: move the SWIOTLB config symbol to lib/Kconfig Christoph Hellwig
2018-04-25  5:15 ` [PATCH 13/13] swiotlb: remove the CONFIG_DMA_DIRECT_OPS ifdefs Christoph Hellwig
2018-05-02 12:46 ` centralize SWIOTLB config symbol and misc other cleanups V3 Christoph Hellwig
2018-05-09  5:03   ` Christoph Hellwig

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