Sharing dma-bufs using a driver-private interconnect

[Christian König]

Hi Thomas,

On 5/16/25 10:33, Thomas Hellström wrote:
> Hi!
> 
> I previously discussed this with Simona on IRC but would like to get
> some feedback also from a wider audience:
> 
> We're planning to share dma-bufs using a fast interconnect in a way
> similar to pcie-p2p:
> 
> The rough plan is to identify dma-bufs capable of sharing this way by
> looking at the address of either the dma-buf ops and / or the
> importer_ops to conclude it's a device using the same driver (or
> possibly child driver) and then take special action when the dma-
> addresses are obtained. Nothing visible outside of the xe driver or its
> child driver.

As far as I can see that should work and we have recommended doing exactly that to multiple people in the past.
 
> Are there any absolute "DON'T"s or recommendations to keep in mind WRT
> to this approach?

My only requirement is that you write up some documentation (preferable either in drivers/dma-buf/dma-buf.c or Documentation/driver-api/dma-buf.rst) how drivers should do this, what the implications with the rest of the DMA-buf interface is etc... etc...

The goal is to nail down how to do driver private interfaces without breaking interoperability with drivers who don't participate in that.

Regards,
Christian.

> 
> Thanks,
> Thomas
> 
)