From: Christoph Hellwig <hch@lst.de>
To: Shawn Anastasio <shawn@anastas.io>
Cc: Christoph Hellwig <hch@lst.de>,
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 08:04:32 +0200 [thread overview]
Message-ID: <20190807060432.GD6627@lst.de> (raw)
In-Reply-To: <7df95ffb-6df3-b118-284c-ee32cad81199@anastas.io>
On Tue, Aug 06, 2019 at 09:39:06PM +0200, Shawn Anastasio wrote:
>> -#ifdef CONFIG_ARCH_HAS_DMA_MMAP_PGPROT
>> pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
>> unsigned long attrs);
>> -#else
>> -# define arch_dma_mmap_pgprot(dev, prot, attrs) pgprot_noncached(prot)
>> -#endif
>
> Nit, but maybe the prototype should still be ifdef'd here? It at least
> could prevent a reader from incorrectly thinking that the function is
> always present.
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.
>
> 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.
> 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.
next prev parent reply other threads:[~2019-08-07 6:04 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 [this message]
2019-08-07 11:45 ` Shawn Anastasio
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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