From: Shawn Anastasio <shawn@anastas.io>
To: Christoph Hellwig <hch@lst.de>
Cc: iommu@lists.linux-foundation.org,
Michael Ellerman <mpe@ellerman.id.au>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Paul Burton <paul.burton@mips.com>,
James Hogan <jhogan@kernel.org>,
linuxppc-dev@lists.ozlabs.org, linux-mips@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Gavin Li <git@thegavinli.com>
Subject: Re: [PATCH 1/2] dma-mapping: fix page attributes for dma_mmap_*
Date: Wed, 7 Aug 2019 13:45:51 +0200 [thread overview]
Message-ID: <765a7f25-0e3d-3edc-3f6d-9a17e2379253@anastas.io> (raw)
In-Reply-To: <20190807060432.GD6627@lst.de>
On 8/7/19 8:04 AM, Christoph Hellwig wrote:
> Actually it is typical modern Linux style to just provide a prototype
> and then use "if (IS_ENABLED(CONFIG_FOO))" to guard the call(s) to it.
I see.
>> Also, like Will mentioned earlier, the function name isn't entirely
>> accurate anymore. I second the suggestion of using something like
>> arch_dma_noncoherent_pgprot().
>
> As mentioned I plan to remove arch_dma_mmap_pgprot for 5.4, so I'd
> rather avoid churn for the short period of time.
Yeah, fair enough.
>> As for your idea of defining
>> pgprot_dmacoherent for all architectures as
>>
>> #ifndef pgprot_dmacoherent
>> #define pgprot_dmacoherent pgprot_noncached
>> #endif
>>
>> I think that the name here is kind of misleading too, since this
>> definition will only be used when there is no support for proper
>> DMA coherency.
>
> Do you have a suggestion for a better name? I'm pretty bad at naming,
> so just reusing the arm name seemed like a good way to avoid having
> to make naming decisions myself.
Good question. Perhaps something like `pgprot_dmacoherent_fallback`
would better convey that this is only used for devices that don't
support DMA coherency? Or maybe `pgprot_dma_noncoherent`?
next prev parent reply other threads:[~2019-08-07 11:46 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-05 8:01 fix default dma_mmap_* pgprot v2 Christoph Hellwig
2019-08-05 8:01 ` [PATCH 1/2] dma-mapping: fix page attributes for dma_mmap_* Christoph Hellwig
2019-08-05 9:10 ` Catalin Marinas
[not found] ` <CAP_+7SzPdNCMKuuXMjHjpCzxsey2YWR_e6mTAWtNSZ6kKBvKFw@mail.gmail.com>
2019-08-06 2:55 ` Gavin Li
2019-08-06 5:12 ` Christoph Hellwig
2019-08-06 19:39 ` Shawn Anastasio
2019-08-07 6:04 ` Christoph Hellwig
2019-08-07 11:45 ` Shawn Anastasio [this message]
2019-08-05 8:01 ` [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE Christoph Hellwig
2019-08-05 8:06 ` Sergei Shtylyov
2019-08-07 6:16 fix default dma_mmap_* pgprot v3 Christoph Hellwig
2019-08-07 6:16 ` [PATCH 1/2] dma-mapping: fix page attributes for dma_mmap_* Christoph Hellwig
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