From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: David Woodhouse <dwmw2@infradead.org>,
Brian Norris <computersforpeace@gmail.com>,
linux-mtd@lists.infradead.org,
Andrew Morton <akpm@linux-foundation.org>,
Dave Gordon <david.s.gordon@intel.com>,
linux-crypto@vger.kernel.org,
Herbert Xu <herbert@gondor.apana.org.au>,
Vinod Koul <vinod.koul@intel.com>,
Richard Weinberger <richard@nod.at>,
Joerg Roedel <joro@8bytes.org>,
linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org,
Vignesh R <vigneshr@ti.com>,
linux-mm@kvack.org, iommu@lists.linux-foundation.org,
Mark Brown <broonie@kernel.org>,
Hans Verkuil <hans.verkuil@cisco.com>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
dmaengine@vger.kernel.org,
Dan Williams <dan.j.williams@intel.com>,
linux-media@vger.kernel.org,
"David S. Miller" <davem@davemloft.net>,
linux-arm-kernel@lists.infradead.org,
Mauro Carvalho Chehab <m.chehab@samsung.com>
Subject: Re: [PATCH 2/4] scatterlist: add sg_alloc_table_from_buf() helper
Date: Thu, 31 Mar 2016 15:14:13 +0100 [thread overview]
Message-ID: <20160331141412.GK19428@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <1459427384-21374-3-git-send-email-boris.brezillon@free-electrons.com>
On Thu, Mar 31, 2016 at 02:29:42PM +0200, Boris Brezillon wrote:
> sg_alloc_table_from_buf() provides an easy solution to create an sg_table
> from a virtual address pointer. This function takes care of dealing with
> vmallocated buffers, buffer alignment, or DMA engine limitations (maximum
> DMA transfer size).
Please note that the DMA API does not take account of coherency of memory
regions other than non-high/lowmem - there are specific extensions to
deal with this.
What this means is that having an API that takes any virtual address
pointer, converts it to a scatterlist which is then DMA mapped, is
unsafe.
It'll be okay for PIPT and non-aliasing VIPT cache architectures, but
for other cache architectures this will hide this problem and make
review harder.
--
RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
next prev parent reply other threads:[~2016-03-31 14:14 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-31 12:29 [PATCH 0/4] scatterlist: sg_table from virtual pointer Boris Brezillon
2016-03-31 12:29 ` [PATCH 1/4] mm: add is_highmem_addr() helper Boris Brezillon
2016-04-04 8:14 ` Vignesh R
[not found] ` <57022253.70400-l0cyMroinI0@public.gmane.org>
2016-04-04 15:05 ` Boris Brezillon
[not found] ` <1459427384-21374-1-git-send-email-boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
2016-03-31 12:29 ` [PATCH 2/4] scatterlist: add sg_alloc_table_from_buf() helper Boris Brezillon
2016-03-31 14:14 ` Russell King - ARM Linux [this message]
[not found] ` <20160331141412.GK19428-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org>
2016-03-31 14:45 ` Boris Brezillon
2016-03-31 15:09 ` Russell King - ARM Linux
2016-03-31 12:29 ` [PATCH 3/4] spi: use sg_alloc_table_from_buf() Boris Brezillon
[not found] ` <1459427384-21374-4-git-send-email-boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
2016-03-31 17:23 ` Mark Brown
2016-03-31 12:29 ` [PATCH 4/4] mtd: provide helper to prepare buffers for DMA operations Boris Brezillon
2016-04-01 3:13 ` kbuild test robot
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