Re: a saner API for allocating DMA addressable pages v3

[Christoph Hellwig <hch@lst.de>]

Any comments?

Thomas: this should be identical to the git tree I gave you for mips
testing, and you add your tested-by (and reviewd-by tags where
applicable)?

Helge: for parisc this should effectively be the same as the first
version, but I've dropped the tested-by tags due to the reshuffle,
and chance you could retest it?

On Tue, Sep 15, 2020 at 05:51:04PM +0200, Christoph Hellwig wrote:
> 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.
> 
> 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.
> 
> 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 v2:
>  - fix up the patch reshuffle which wasn't quite correct
>  - fix up a few commit messages
> 
> 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:
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