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From: Christoph Hellwig <hch@lst.de>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>,
	Tony Luck <tony.luck@intel.com>,
	linux-ia64@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	linux-mips@vger.kernel.org, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 04/12] dma-mapping: fix DMA_OPS dependencies
Date: Fri, 11 Sep 2020 09:09:50 +0200	[thread overview]
Message-ID: <20200911070950.GB22394@lst.de> (raw)
In-Reply-To: <1e3c7094-62da-6e8c-0a41-0bc63dd3db68@arm.com>

On Thu, Sep 10, 2020 at 01:55:37PM +0100, Robin Murphy wrote:
> AFAICS all three of these bus drivers are only proxying a struct 
> dma_map_ops * pointer around, so if they used the set_dma_ops() helper they 
> shouldn't even need these selects at all. Only INTEL_MIC_HOST appears to 
> have a logical dependency on DMA_OPS for actual functionality.
>
> However, I have a vague feeling you might not be fond of those dma_ops 
> helpers, and I have no great objection to this one-liner as-is, so (modulo 
> the couple of commit message typos),

The problem with these inherіtances is that they don't actually work
for the general case.  You'd also need to inherity things like the
dma ranges, the bus limits, etc, etc.  So we need to kill them instead.
That whole mic/vop case is even worse than that with it's weird set
of chained dma ops that seems to implement some kind of device side
iommu that isn't in scope for the DMA API at all.
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  reply	other threads:[~2020-09-11  7:10 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-08 16:47 dma-mapping cleanups Christoph Hellwig
2020-09-08 16:47 ` [PATCH 01/12] MIPS: make dma_sync_*_for_cpu a little less overzealous Christoph Hellwig
2020-09-08 16:47 ` [PATCH 02/12] MIPS/jazzdma: remove the unused vdma_remap function Christoph Hellwig
2020-09-08 16:47 ` [PATCH 03/12] MIPS/jazzdma: decouple from dma-direct Christoph Hellwig
2020-09-08 16:47 ` [PATCH 04/12] dma-mapping: fix DMA_OPS dependencies Christoph Hellwig
2020-09-08 18:04   ` Sergei Shtylyov
2020-09-11  7:10     ` Christoph Hellwig
2020-09-10 12:55   ` Robin Murphy
2020-09-11  7:09     ` Christoph Hellwig [this message]
2020-09-08 16:47 ` [PATCH 05/12] dma-mapping: add (back) arch_dma_mark_clean for ia64 Christoph Hellwig
2020-09-08 16:47 ` [PATCH 06/12] dma-direct: remove dma_direct_{alloc,free}_pages Christoph Hellwig
2020-09-10 12:57   ` Robin Murphy
2020-09-08 16:47 ` [PATCH 07/12] dma-direct: lift gfp_t manipulation out of__dma_direct_alloc_pages Christoph Hellwig
2020-09-10 13:02   ` Robin Murphy
2020-09-08 16:47 ` [PATCH 08/12] dma-direct: use phys_to_dma_direct in dma_direct_alloc Christoph Hellwig
2020-09-10 13:03   ` Robin Murphy
2020-09-08 16:47 ` [PATCH 09/12] dma-direct: remove __dma_to_phys Christoph Hellwig
2020-09-10 13:26   ` Robin Murphy
2020-09-11  7:14     ` Christoph Hellwig
2020-09-08 16:47 ` [PATCH 10/12] dma-direct: rename and cleanup __phys_to_dma Christoph Hellwig
2020-09-10 13:30   ` Robin Murphy
2020-09-08 16:47 ` [PATCH 11/12] dma-mapping: move dma_common_{mmap, get_sgtable} out of mapping.c Christoph Hellwig
2020-09-10 13:34   ` Robin Murphy
2020-09-11  7:15     ` [PATCH 11/12] dma-mapping: move dma_common_{mmap,get_sgtable} " Christoph Hellwig
2020-09-08 16:47 ` [PATCH 12/12] dma-mapping: move the dma_declare_coherent_memory documentation Christoph Hellwig
2020-09-10 13:51   ` Robin Murphy
2020-09-11  7:17     ` Christoph Hellwig

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