Re: [PATCH] dma-buf: heaps: Introduce dma_heap_add_cma() for non-default CMA heap

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Hi John,
Thank you for your comment.

On 2020/07/29 4:17, John Stultz wrote:
On Thu, Jul 16, 2020 at 6:10 PM Kunihiko Hayashi
<hayashi.kunihiko@xxxxxxxxxxxxx> wrote:

Current dma-buf heaps can handle only default CMA. This introduces
dma_heap_add_cma() function to attach CMA heaps that belongs to a device.

At first, the driver calls of_reserved_mem_device_init() to set
memory-region property associated with reserved-memory defined as CMA
to the device. And when the driver calls this dma_heap_add_cma(),
the CMA will be added to dma-buf heaps.

For example, prepare CMA node named "linux,cma@10000000" and
specify the node for memory-region property. After the above calls
in the driver, a device file "/dev/dma_heap/linux,cma@10000000"
associated with the CMA become available as dma-buf heaps.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@xxxxxxxxxxxxx>
---
  drivers/dma-buf/heaps/cma_heap.c | 12 ++++++++++++
  include/linux/dma-heap.h         |  9 +++++++++
  2 files changed, 21 insertions(+)

Hey! Sorry for the slow response on this! I just realized I never replied!

I waited but no problem.


diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
index 626cf7f..5d2442e 100644
--- a/drivers/dma-buf/heaps/cma_heap.c
+++ b/drivers/dma-buf/heaps/cma_heap.c

[snip]

--
2.7.4

Looks sane to me.  Being able to expose different multiple CMA heaps
is needed, and I agree this way (as opposed to my earlier dts
appraoch) is probably the best approach. The only bit I'm so-so on is
adding the CMA heap specific call in the dma-heap.h, but at the same
time I can't justify adding a whole new header for a single function.

I'm also a little worried about whether "CMA specific" call is in
the dma-heap.h, however I can't find another solution.

Do you have a upstream driver that you plan to make use this new call?

Unfortunately I don't have an upstream driver using this call.

This call is called from dma-buf heaps "importer" or "customer",
and I only made an example (do nothing) importer driver
to test the call.

We want to have in-tree users of code added.

I think this is a generic way to use non-default CMA heaps, however,
we need in-tree "importer" drivers to want to use non-default CMA heaps.
I don't find it from now.

But if so, feel free to add my:
   Acked-by: John Stultz <john.stultz@xxxxxxxxxx>
To this patch when you submit the driver changes.

Thank you,

---
Best Regards
Kunihiko Hayashi

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