Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 21 Jan 2019 13:30:28 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Liam Mark <lmark@codeaurora.org>
Cc:     "Andrew F. Davis" <afd@ti.com>,
        Christoph Hellwig <hch@infradead.org>,
        Laura Abbott <labbott@redhat.com>, 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,
        john.stultz@linaro.org
Subject: Re: [PATCH 3/4] dma-buf: add support for mapping with dma mapping
 attributes
Message-ID: <20190121213028.GB28620@infradead.org>
References: <1547836667-13695-1-git-send-email-lmark@codeaurora.org>
 <1547836667-13695-4-git-send-email-lmark@codeaurora.org>
 <20190119102527.GA17723@infradead.org>
 <7ae73c39-9049-bcf6-775f-b0817ba0ec5f@redhat.com>
 <20190121083046.GD12420@infradead.org>
 <alpine.DEB.2.10.1901211142560.9631@lmark-linux.qualcomm.com>
 <0ed7875f-15e9-184f-5b99-9a53df7c8d14@ti.com>
 <alpine.DEB.2.10.1901211214570.11004@lmark-linux.qualcomm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.10.1901211214570.11004@lmark-linux.qualcomm.com>
User-Agent: Mutt/1.9.2 (2017-12-15)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, Jan 21, 2019 at 12:20:42PM -0800, Liam Mark wrote:
> I have left this to clients, but if they own the buffer they can have the 
> knowledge as to whether CPU access is needed in that use case (example for 
> post-processing).

That is an API design which the user is more likely to get wrong than
right and thus does not pass the smell test.