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

[Jiri Pirko <jiri@resnulli.us>]

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.

Thanks!