On Wed, May 08, 2024 at 10:36:08AM +0200, Daniel Vetter wrote: > On Tue, May 07, 2024 at 04:07:39PM -0400, Nicolas Dufresne wrote: > > Le mardi 07 mai 2024 à 21:36 +0300, Laurent Pinchart a écrit : > > > Shorter term, we have a problem to solve, and the best option we have > > > found so far is to rely on dma-buf heaps as a backend for the frame > > > buffer allocatro helper in libcamera for the use case described above. > > > This won't work in 100% of the cases, clearly. It's a stop-gap measure > > > until we can do better. > > > > Considering the security concerned raised on this thread with dmabuf heap > > allocation not be restricted by quotas, you'd get what you want quickly with > > memfd + udmabuf instead (which is accounted already). > > > > It was raised that distro don't enable udmabuf, but as stated there by Hans, in > > any cases distro needs to take action to make the softISP works. This > > alternative is easy and does not interfere in anyway with your future plan or > > the libcamera API. You could even have both dmabuf heap (for Raspbian) and the > > safer memfd+udmabuf for the distro with security concerns. > > > > And for the long term plan, we can certainly get closer by fixing that issue > > with accounting. This issue also applied to v4l2 io-ops, so it would be nice to > > find common set of helpers to fix these exporters. > > Yeah if this is just for softisp, then memfd + udmabuf is also what I was > about to suggest. Not just as a stopgap, but as the real official thing. Long term I still want a centralized memory allocator, at which point libcamera should stop allocating buffers at all. > udmabuf does kinda allow you to pin memory, but we can easily fix that by > adding the right accounting and then either let mlock rlimits or cgroups > kernel memory limits enforce good behavior. -- Regards, Laurent Pinchart
