On Tue, Dec 08, 2020 at 04:13:20PM +0900, Sergey Senozhatsky wrote:

On (20/12/08 13:54), Tomasz Figa wrote:

quoted

In any case, Sergey is going to share a preliminary patch on how the
current API would be used in the V4L2 videobuf2 framework. That should
give us more input on how such a helper could look.

HUGE apologies for the previous screw up! I replied in the
gmail web-interface and that did not work out as expected
(at all, big times).

Actually the previous mail was a mime multipart one, and the plain text
version displayed just fine here.  My the gmail engineers finally learned
something after all.

Another thing to notice is that the new API requires us to have two execution branches
in allocators - one for the current API; and one for the new API (if it's supported and
if user-space requested non-coherent allocation).

So I think we do want these branches for coherent vs non-coherent as they
have very different semantics and I do not think that hiding them under
the same API helps people to understand those vastly different semantics.

OTOH we should look into a fallback for DMA API instances that do not
support the discontigous allocations.

I think between your comments and those from Ricardo I have a good idea
for a somewhat updated API.  I'll try to post something in the next days.