Re: [PATCH 4/5] dma-buf: heaps: allow heap to specify valid heap flags

[Leon Romanovsky <leon@kernel.org>]

On Tue, Feb 10, 2026 at 10:05:14AM +0100, Jiri Pirko wrote:
> Mon, Feb 09, 2026 at 09:08:03PM +0100, jstultz@google.com wrote:
> >On Mon, Feb 9, 2026 at 7:38 AM Jiri Pirko <jiri@resnulli.us> wrote:
> >>
> >> From: Jiri Pirko <jiri@nvidia.com>
> >>
> >> Currently the flags, which are unused, are validated for all heaps.
> >> Since the follow-up patch introduces a flag valid for only one of the
> >> heaps, allow to specify the valid flags per-heap.
> >
> >I'm not really in this space anymore, so take my feedback with a grain of salt.
> >
> >While the heap allocate flags argument is unused, it was intended to
> >be used for generic allocation flags that would apply to all or at
> >least a wide majority of heaps.
> >
> >It was definitely not added to allow for per-heap or heap specific
> >flags (as this patch tries to utilize it). That was the mess we had
> >with ION driver that we were trying to avoid.
> >
> >The intent of dma-buf heaps is to try to abstract all the different
> >device memory constraints so there only needs to be a [usage] ->
> >[heap] mapping, and otherwise userland can be generalized so that it
> >doesn't need to be re-written to work with different devices/memory
> >types.  Adding heap-specific allocation flags prevents that
> >generalization.
> >
> >So instead of adding heap specific flags, the general advice has been
> >to add a separate heap name for the flag property.
> 
> Right, my original idea was to add a separate heap. Then I spotted the
> flags and seemed like a great fit. Was not aware or the history or
> original intention. Would be probably good to document it for
> future generations.
> 
> So instead of flag, I will add heap named something
> like "system_cc_decrypted" to implement this.

It is problematic to expose a user‑visible API that depends on a name.
Such a design limits our ability to extend the functionality in the
future, should new use cases arise.

Thanks

> 
> Thanks!