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Subject: Re: [PATCH 3/4] dma-buf: add support for mapping with dma mapping
 attributes
To:     Christoph Hellwig <hch@infradead.org>,
        Liam Mark <lmark@codeaurora.org>
Cc:     sumit.semwal@linaro.org, arve@android.com, tkjos@android.com,
        maco@android.com, joel@joelfernandes.org, christian@brauner.io,
        devel@driverdev.osuosl.org, dri-devel@lists.freedesktop.org,
        linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org,
        afd@ti.com, john.stultz@linaro.org
References: <1547836667-13695-1-git-send-email-lmark@codeaurora.org>
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 <20190119102527.GA17723@infradead.org>
From:   Laura Abbott <labbott@redhat.com>
Message-ID: <7ae73c39-9049-bcf6-775f-b0817ba0ec5f@redhat.com>
Date:   Sat, 19 Jan 2019 08:50:41 -0800
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On 1/19/19 2:25 AM, Christoph Hellwig wrote:
> On Fri, Jan 18, 2019 at 10:37:46AM -0800, Liam Mark wrote:
>> Add support for configuring dma mapping attributes when mapping
>> and unmapping memory through dma_buf_map_attachment and
>> dma_buf_unmap_attachment.
>>
>> Signed-off-by: Liam Mark <lmark@codeaurora.org>
> 
> And who is going to decide which ones to pass?  And who documents
> which ones are safe?
> 
> I'd much rather have explicit, well documented dma-buf flags that
> might get translated to the DMA API flags, which are not error checked,
> not very well documented and way to easy to get wrong.
> 

I'm not sure having flags in dma-buf really solves anything
given drivers can use the attributes directly with dma_map
anyway, which is what we're looking to do. The intention
is for the driver creating the dma_buf attachment to have
the knowledge of which flags to use.

Thanks,
Laura