linux-kernel - Re: [PATCH v12 4/5] dma-buf: heaps: Add CMA heap to dmabuf heaps

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Date:   Fri, 18 Oct 2019 09:54:52 -0400
From:   "Andrew F. Davis" <afd@...com>
To:     Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Brian Starkey <Brian.Starkey@....com>
CC:     John Stultz <john.stultz@...aro.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Laura Abbott <labbott@...hat.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        Pratik Patel <pratikp@...eaurora.org>,
        Vincent Donnefort <Vincent.Donnefort@....com>,
        Sudipto Paul <Sudipto.Paul@....com>,
        Christoph Hellwig <hch@...radead.org>,
        Chenbo Feng <fengc@...gle.com>,
        Alistair Strachan <astrachan@...gle.com>,
        Hridya Valsaraju <hridya@...gle.com>,
        Hillf Danton <hdanton@...a.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        nd <nd@....com>
Subject: Re: [PATCH v12 4/5] dma-buf: heaps: Add CMA heap to dmabuf heaps

On 10/18/19 8:03 AM, Benjamin Gaignard wrote:
> Le ven. 18 oct. 2019 à 13:21, Brian Starkey <Brian.Starkey@....com> a écrit :
>>
>> On Fri, Oct 18, 2019 at 05:23:22AM +0000, John Stultz wrote:
>>> This adds a CMA heap, which allows userspace to allocate
>>> a dma-buf of contiguous memory out of a CMA region.
>>>
>>> This code is an evolution of the Android ION implementation, so
>>> thanks to its original author and maintainters:
>>>   Benjamin Gaignard, Laura Abbott, and others!
>>>
>>> NOTE: This patch only adds the default CMA heap. We will enable
>>> selectively adding other CMA memory regions to the dmabuf heaps
>>> interface with a later patch (which requires a dt binding)
> 
> Maybe we can use "no-map" DT property to trigger that. If set do not expose the
> cma heap.


"no-map" means it can't be used as a regular CMA either, we want some
way to both have it as a device usable CMA but also not be exposed to
userspace if needed.

Andrew

> 
> Benjamin
>>
>> That'll teach me for reading my email in FIFO order.
>>
>> This approach makes sense to me.
>>
>> -Brian
>>