On Fri, Oct 31, 2025 at 08:46:34AM +0100, Christian König wrote: > On 10/31/25 06:15, Kasireddy, Vivek wrote: > > Hi Jason, > > > >> Subject: Re: [RFC v2 0/8] dma-buf: Add support for mapping dmabufs via > >> interconnects > >> > >> On Thu, Oct 30, 2025 at 06:17:11AM +0000, Kasireddy, Vivek wrote: > >>> It mostly looks OK to me but there are a few things that I want to > >>> discuss, > >>> after briefly looking at the patches in your branch: > >>> - I am wondering what is the benefit of the SGT compatibility stuff > >>> especially > >>> when Christian suggested that he'd like to see SGT usage gone from > >>> dma-buf > >> > >> I think to get rid of SGT we do need to put it in a little well > >> defined box and then create alternatives and remove things using > >> SGT. This is a long journey, and I think this is the first step. > >> > >> If SGT is some special case it will be harder to excise. > >> > >> So the next steps would be to make all the exporters directly declare > >> a SGT and then remove the SGT related ops from dma_ops itself and > >> remove the compat sgt in the attach logic. This is not hard, it is all > >> simple mechanical work. > > IMO, this SGT compatibility stuff should ideally be a separate follow-on > > effort (and patch series) that would also probably include updates to > > various drivers to add the SGT mapping type. > > Nope, just the other way around. In other words the SGT > compatibility is a pre-requisite. > > We should first demonstrate with existing drivers that the new > interface works and does what it promised to do and then extend it > with new functionality.
Ok, so I think that is what my github is showing. Everything interworks, non-mapping-type aware code simply acts exactly as though it is using a SGT mapping type from the perspective of aware code. I see a fairly easy path to do some driver upgrades to make more things more mapping aware and remove some of the compatibility parts. Let me see if I can post a RFC version next week, got a big pile of other stuff to do still.. Jason
