This patch introduces a new heap driver to expose DT non‑reusable
"shared-dma-pool" coherent regions as dma-buf heaps, so userspace can
allocate buffers from each reserved, named region.

Because these regions are device‑dependent, each heap instance binds a
heap device to its reserved‑mem region via a newly introduced helper
function -namely, of_reserved_mem_device_init_with_mem()- so coherent
allocations use the correct dev->dma_mem.

Charging to cgroups for these buffers is intentionally left out to keep
review focused on the new heap; I plan to follow up based on Eric’s [1]
and Maxime’s [2] work on dmem charging from userspace.

This series also makes the new heap driver modular, in line with the CMA
heap change in [3].

[1] https://lore.kernel.org/all/20260218-dmabuf-heap-cma-dmem-v2-0-b249886fb7b2@redhat.com/
[2] https://lore.kernel.org/all/20250310-dmem-cgroups-v1-0-2984c1bc9312@kernel.org/
[3] https://lore.kernel.org/all/20260303-dma-buf-heaps-as-modules-v3-0-24344812c707@kernel.org/

Signed-off-by: Albert Esteve <aesteve@redhat.com>
---
Changes in v2:
- Removed dmem charging parts
- Moved coherent heap registering logic to coherent.c
- Made heap device a member of struct dma_heap
- Split dma_heap_add logic into create/register, to be able to
  access the stored heap device before registered.
- Avoid platform device in favour of heap device
- Added a wrapper to rmem device_init() op
- Switched from late_initcall() to module_init()
- Made the coherent heap driver modular
- Link to v1: https://lore.kernel.org/r/20260224-b4-dmabuf-heap-coherent-rmem-v1-1-dffef43298ac@redhat.com

---
Albert Esteve (5):
      dma-buf: dma-heap: split dma_heap_add
      of_reserved_mem: add a helper for rmem device_init op
      dma-buf: heaps: Add Coherent heap to dmabuf heaps
      dma: coherent: register to coherent heap
      dma-buf: heaps: coherent: Turn heap into a module

John Stultz (1):
      dma-buf: dma-heap: Keep track of the heap device struct

 drivers/dma-buf/dma-heap.c            | 138 +++++++++--
 drivers/dma-buf/heaps/Kconfig         |   9 +
 drivers/dma-buf/heaps/Makefile        |   1 +
 drivers/dma-buf/heaps/coherent_heap.c | 429 ++++++++++++++++++++++++++++++++++
 drivers/of/of_reserved_mem.c          |  27 ++-
 include/linux/dma-heap.h              |  16 ++
 include/linux/dma-map-ops.h           |   7 +
 include/linux/of_reserved_mem.h       |   8 +
 kernel/dma/coherent.c                 |  34 +++
 9 files changed, 642 insertions(+), 27 deletions(-)
---
base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
change-id: 20260223-b4-dmabuf-heap-coherent-rmem-91fd3926afe9

Best regards,
-- 
Albert Esteve <aesteve@redhat.com>

On Tue, Mar 3, 2026 at 4:34 AM Albert Esteve <aesteve@redhat.com> wrote:
>
> This patch introduces a new heap driver to expose DT non‑reusable
> "shared-dma-pool" coherent regions as dma-buf heaps, so userspace can
> allocate buffers from each reserved, named region.

Just a nit here: Might be good to provide some higher level context as
to why this is wanted, and what it enables.

Also, "shared-dma-pool" is also used for CMA regions, so it might be
unclear initially how this is different from the CMA heap (you do
mention non-reusable, but that's a prettty subtle detail).

Might be good to add some of the rationale to the patch adding the
heap implementation as well so it makes it into the git history.

thanks
-john

On Tue, Mar 3, 2026 at 9:55 PM John Stultz <jstultz@google.com> wrote:
>
> On Tue, Mar 3, 2026 at 4:34 AM Albert Esteve <aesteve@redhat.com> wrote:
> >
> > This patch introduces a new heap driver to expose DT non‑reusable
> > "shared-dma-pool" coherent regions as dma-buf heaps, so userspace can
> > allocate buffers from each reserved, named region.
>
> Just a nit here: Might be good to provide some higher level context as
> to why this is wanted, and what it enables.
>
> Also, "shared-dma-pool" is also used for CMA regions, so it might be
> unclear initially how this is different from the CMA heap (you do
> mention non-reusable, but that's a prettty subtle detail).

Sure, I will expand this for the next revision and try to clarify the
points you mentioned here (and add these points to the relevant
patch).

BR,
Albert

>
> Might be good to add some of the rationale to the patch adding the
> heap implementation as well so it makes it into the git history.
>
> thanks
> -john
>