Subject: [PATCH 11/13] mips, unicore32: swiotlb doesn't need sg->dma_length

From: [email-masked] (James Hogan)
Date: Thu, 3 May 2018 07:47:32 +0100

On Thu, May 03, 2018 at 05:56:43AM +0200, Christoph Hellwig wrote:
> 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.

Okay, for MIPS:
Acked-by: James Hogan <[email-masked]>

Cheers
James
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