Re: a saner API for allocating DMA addressable pages
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- To: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
- Subject: Re: a saner API for allocating DMA addressable pages
- From: Christoph Hellwig <hch@xxxxxx>
- Date: Tue, 25 Aug 2020 15:26:12 +0200
- Cc: Christoph Hellwig <hch@xxxxxx>, Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>, Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>, "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>, Joonyoung Shim <jy0922.shim@xxxxxxxxxxx>, Seung-Woo Kim <sw0312.kim@xxxxxxxxxxx>, Kyungmin Park <kyungmin.park@xxxxxxxxxxx>, Ben Skeggs <bskeggs@xxxxxxxxxx>, Pawel Osciak <pawel@xxxxxxxxxx>, Matt Porter <mporter@xxxxxxxxxxxxxxxxxxx>, iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx, Tom Lendacky <thomas.lendacky@xxxxxxx>, linux-doc@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-media@xxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, linux-mips@xxxxxxxxxxxxxxx, linux-parisc@xxxxxxxxxxxxxxx, linux-samsung-soc@xxxxxxxxxxxxxxx, nouveau@xxxxxxxxxxxxxxxxxxxxx, netdev@xxxxxxxxxxxxxxx, linux-nvme@xxxxxxxxxxxxxxxxxxx, linux-scsi@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, alsa-devel@xxxxxxxxxxxxxxxx
- In-reply-to: <8fa1ce36-c783-1a02-6890-211eb504a33b@samsung.com>
- References: <CGME20200819065610eucas1p2fde88e81917071b1888e7cc01ba0f298@eucas1p2.samsung.com> <20200819065555.1802761-1-hch@lst.de> <8fa1ce36-c783-1a02-6890-211eb504a33b@samsung.com>
- User-agent: Mutt/1.5.17 (2007-11-01)
On Tue, Aug 25, 2020 at 01:30:41PM +0200, Marek Szyprowski wrote:
> I really wonder what is the difference between this new API and
> alloc_pages(GFP_DMA, n). Is this API really needed? I thought that this
> is legacy thing to be removed one day...
The difference is that the pages returned are guranteed to be addressable
by the devie. This is a very important difference that matters for
a lot of use cases.
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