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Date: Thu, 4 Dec 2025 12:07:09 +0100
From: Christoph Hellwig <hch@lst.de>
To: Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>
Cc: Pavel Begunkov <asml.silence@gmail.com>, linux-block@vger.kernel.org,
	io-uring@vger.kernel.org, Vishal Verma <vishal1.verma@intel.com>,
	tushar.gohad@intel.com, Keith Busch <kbusch@kernel.org>,
	Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
	Sagi Grimberg <sagi@grimberg.me>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Christian Brauner <brauner@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Sumit Semwal <sumit.semwal@linaro.org>,
	linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-fsdevel@vger.kernel.org, linux-media@vger.kernel.org,
	dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org
Subject: Re: [RFC v2 01/11] file: add callback for pre-mapping dmabuf
Message-ID: <20251204110709.GA22971@lst.de>
References: <cover.1763725387.git.asml.silence@gmail.com> <74d689540fa200fe37f1a930165357a92fe9e68c.1763725387.git.asml.silence@gmail.com> <7b2017f4-02a3-482a-a173-bb16b895c0cb@amd.com>
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On Thu, Dec 04, 2025 at 11:46:45AM +0100, Christian König wrote:
> On 11/23/25 23:51, Pavel Begunkov wrote:
> > Add a file callback that maps a dmabuf for the given file and returns
> > an opaque token of type struct dma_token representing the mapping.
> 
> I'm really scratching my head what you mean with that?
> 
> And why the heck would we need to pass a DMA-buf to a struct file?

I find the naming pretty confusing a well.  But what this does is to
tell the file system/driver that it should expect a future
read_iter/write_iter operation that takes data from / puts data into
the dmabuf passed to this operation.