Re: [PATCH] misc: sram: Add dma-heap-export reserved SRAM area type

[Rob Herring]

On Fri, Apr 24, 2020 at 5:27 PM Andrew F. Davis <afd@xxxxxx> wrote:
>
> This new export type exposes to userspace the SRAM area as a DMA-Heap,
> this allows for allocations as DMA-BUFs that can be consumed by various
> DMA-BUF supporting devices.
>
> Signed-off-by: Andrew F. Davis <afd@xxxxxx>
> ---
>  .../devicetree/bindings/sram/sram.yaml        |   8 +

Separate patch and needs to go to DT list...

>  drivers/misc/Kconfig                          |   7 +
>  drivers/misc/Makefile                         |   1 +
>  drivers/misc/sram-dma-heap.c                  | 243 ++++++++++++++++++
>  drivers/misc/sram.c                           |  20 +-
>  drivers/misc/sram.h                           |  17 ++
>  6 files changed, 292 insertions(+), 4 deletions(-)
>  create mode 100644 drivers/misc/sram-dma-heap.c
>
> diff --git a/Documentation/devicetree/bindings/sram/sram.yaml b/Documentation/devicetree/bindings/sram/sram.yaml
> index 7b83cc6c9bfa..b8e33c8d205d 100644
> --- a/Documentation/devicetree/bindings/sram/sram.yaml
> +++ b/Documentation/devicetree/bindings/sram/sram.yaml
> @@ -105,6 +105,14 @@ patternProperties:
>            manipulation of the page attributes.
>          type: boolean
>
> +      dma-heap-export:
> +        description:
> +          Similar to 'pool' and 'export' this region will be exported for use
> +          by drivers, devices, and userspace using the DMA-Heaps framework.
> +          NOTE: This region must be page aligned on start and end in order to
> +          properly allow manipulation of the page attributes.
> +        type: boolean

Though I'm not sure this should be in DT. You have to change your
firmware to enable a new kernel feature? We also already have 'export'
which sounds like the same function. Or 'pool' though reading the
description, I don't really understand it's use.

What combination of all 3 of these options would be valid?

Rob