netdev - a saner API for allocating DMA addressable pages v2

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Message-Id: <20200914144433.1622958-1-hch@lst.de>
Date:   Mon, 14 Sep 2020 16:44:16 +0200
From:   Christoph Hellwig <hch@....de>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Joonyoung Shim <jy0922.shim@...sung.com>,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Matt Porter <mporter@...nel.crashing.org>,
        iommu@...ts.linux-foundation.org
Cc:     Stefan Richter <stefanr@...6.in-berlin.de>,
        linux1394-devel@...ts.sourceforge.net, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...r.kernel.org,
        linux-parisc@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        nouveau@...ts.freedesktop.org, netdev@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-mm@...ck.org,
        alsa-devel@...a-project.org
Subject: a saner API for allocating DMA addressable pages v2

Hi all,

this series replaced the DMA_ATTR_NON_CONSISTENT flag to dma_alloc_attrs
with a separate new dma_alloc_pages API, which is available on all
platforms.  In addition to cleaning up the convoluted code path, this
ensures that other drivers that have asked for better support for
non-coherent DMA to pages with incurring bounce buffering over can finally
be properly supported.

I'm still a little unsure about the API naming, as alloc_pages sort of
implies a struct page return value, but we return a kernel virtual
address.  The other alternative would be to name the API
dma_alloc_noncoherent, but the whole non-coherent naming seems to put
people off.  As a follow up I plan to move the implementation of the
DMA_ATTR_NO_KERNEL_MAPPING flag over to this framework as well, given
that is also is a fundamentally non coherent allocation.  The replacement
for that flag would then return a struct page, as it is allowed to
actually return pages without a kernel mapping as the name suggested
(although most of the time they will actually have a kernel mapping..)

In addition to the conversions of the existing non-coherent DMA users,
I've also added a patch to convert the firewire ohci driver to use
the new dma_alloc_pages API.

Note that I haven't carried over any Tested-by: tags for the noncoherent
allocation conversions as there was a bit of a patch reshuffle, but the
result should be the same.

The first patch is queued up for 5.9 in the media tree, but included here
for completeness.

A git tree is available here:

    git://git.infradead.org/users/hch/misc.git dma_alloc_pages

Gitweb:

    http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/dma_alloc_pages

Changes since v1:
 - rebased on the latests dma-mapping tree, which merged many of the
   cleanups
 - fix an argument passing typo in 53c700, caught by sparse
 - rename a few macro arguments in 53c700
 - pass the right device to the DMA API in the lib82596 drivers
 - fix memory ownershiptransfers in sgiseeq
 - better document what a page in the direct kernel mapping means
 - split into dma_alloc_pages that returns a struct page and is in the
   direct mapping vs dma_alloc_noncoherent that can be vmapped
 - conver the firewire ohci driver to dma_alloc_pages

Diffstat: