linux-kernel - Re: [PATCH v6 4/5] dma-buf: heaps: Add CMA heap to dmabuf heaps

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Date:   Thu, 25 Jul 2019 05:50:14 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     "Andrew F. Davis" <afd@...com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        John Stultz <john.stultz@...aro.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Laura Abbott <labbott@...hat.com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        Pratik Patel <pratikp@...eaurora.org>,
        Brian Starkey <Brian.Starkey@....com>,
        Vincent Donnefort <Vincent.Donnefort@....com>,
        Sudipto Paul <Sudipto.Paul@....com>,
        Xu YiPing <xuyiping@...ilicon.com>,
        "Chenfeng (puck)" <puck.chen@...ilicon.com>,
        butao <butao@...ilicon.com>,
        "Xiaqing (A)" <saberlily.xia@...ilicon.com>,
        Yudongbin <yudongbin@...ilicon.com>,
        Chenbo Feng <fengc@...gle.com>,
        Alistair Strachan <astrachan@...gle.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v6 4/5] dma-buf: heaps: Add CMA heap to dmabuf heaps

On Wed, Jul 24, 2019 at 11:46:01AM -0400, Andrew F. Davis wrote:
> https://patchwork.kernel.org/patch/10863957/
> 
> It's actually a more simple heap type IMHO, but the logic inside is
> incompatible with the system/CMA heaps, if you move any of their code
> into the core framework then this heap stops working. Leading to out of
> tree hacks on the core to get it back functional. I see the same for the
> "complex" heaps with ION.

Well, this mostly is just another allocator (gen_pool).  And given that
the whole dma-buf infrastucture assumes things are backed by pages we
really shouldn't need much more than an alloc and a free callback (and
maybe the pgprot to map it) and handle the rest in common code.