[RFC v2 01/11] file: add callback for pre-mapping dmabuf

[Christian König]

On 12/4/25 12:07, Christoph Hellwig wrote:
> 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.

That explanation makes much more sense.

The remaining question is why does the underlying file system / driver needs to know that it will get addresses from a DMA-buf?

Regards,
Christian.