From: Christoph Hellwig <hch@infradead.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Sven Peter <sven@svenpeter.dev>, Will Deacon <will@kernel.org>,
Joerg Roedel <joro@8bytes.org>, Arnd Bergmann <arnd@kernel.org>,
devicetree@vger.kernel.org, Hector Martin <marcan@marcan.st>,
linux-kernel@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
Mohamed Mediouni <mohamed.mediouni@caramail.com>,
Stan Skowronek <stan@corellium.com>,
linux-arm-kernel@lists.infradead.org,
Mark Kettenis <mark.kettenis@xs4all.nl>,
iommu@lists.linux-foundation.org,
Alexander Graf <graf@amazon.com>,
Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>,
Rob Herring <robh+dt@kernel.org>,
r.czerwinski@pengutronix.de,
Mauro Carvalho Chehab <mchehab@kernel.org>,
linux-media@vger.kernel.org
Subject: Re: [PATCH v4 0/3] Apple M1 DART IOMMU driver
Date: Fri, 16 Jul 2021 07:24:03 +0100 [thread overview]
Message-ID: <YPEmA0rdXHiGtHSx@infradead.org> (raw)
In-Reply-To: <7261df01-34a9-4e53-37cd-ae1aa15b1fb4@arm.com>
On Wed, Jul 14, 2021 at 07:19:50PM +0100, Robin Murphy wrote:
> Even at the DMA API level you could hide *some* of it (at the cost of
> effectively only having 1/4 of the usable address space), but there are
> still cases like where v4l2 has a hard requirement that a page-aligned
> scatterlist can be mapped into a contiguous region of DMA addresses.
Where does v4l2 make that broken assumption? Plenty of dma mapping
implementations including dma-direct do not support that.
Drivers need to call dma_get_merge_boundary() to check for that kind of
behavior.
next parent reply other threads:[~2021-07-16 6:25 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210627143405.77298-1-sven@svenpeter.dev>
[not found] ` <7261df01-34a9-4e53-37cd-ae1aa15b1fb4@arm.com>
2021-07-16 6:24 ` Christoph Hellwig [this message]
2021-07-16 15:32 ` [PATCH v4 0/3] Apple M1 DART IOMMU driver Robin Murphy
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