Hi John, On Thu, Feb 14, 2019 at 09:38:29AM -0800, John Stultz wrote: > [snip] > Some thoughts, as this ABI break has the potential to be pretty painful. > > 1) Unfortunately, this ABI is exposed *through* libion via > ion_alloc/ion_alloc_fd out to gralloc implementations. Which means it > will have a wider impact to vendor userland code. I figured libion could fairly easily loop through all the set bits in heap_mask and call the ioctl for each until it succeeds. That preserves the old behaviour from the libion clients' perspective. > > 2) For patches that cause ABI breaks, it might be good to make it > clear in the commit what the userland impact looks like in userspace, > possibly with an example, so the poor folks who bisect down the change > as breaking their system in a year or so have a clear example as to > what they need to change in their code. > > 3) Also, its not clear how a given userland should distinguish between > the different ABIs. We already have logic in libion to distinguish > between pre-4.12 legacy and post-4.12 implementations (using implicit > ion_free() behavior). I don't see any such check we can make with this > code. Adding another ABI version may require we provide an actual > interface version ioctl. > A slightly fragile/ugly approach might be to attempt a small allocation with a heap_mask of 0xffffffff. On an "old" implementation, you'd expect that to succeed, whereas it would/could be made to fail in the "new" one. Thanks, -Brian > > thanks > -john _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
