Re: [PATCH v4 7/8] drm/fourcc: amlogic: Add modifier definitions for the Scatter layout

[Simon Ser]

On Wednesday, March 25, 2020 9:50 AM, Neil Armstrong <narmstrong@xxxxxxxxxxxx> wrote:

> Amlogic uses a proprietary lossless image compression protocol and format
> for their hardware video codec accelerators, either video decoders or
> video input encoders.
>
> This introduces the Scatter Memory layout, means the header contains IOMMU
> references to the compressed frames content to optimize memory access
> and layout.
>
> In this mode, only the header memory address is needed, thus the content
> memory organization is tied to the current producer execution and cannot
> be saved/dumped neither transferrable between Amlogic SoCs supporting this
> modifier.

I don't think this is suitable for modifiers. User-space relies on
being able to copy a buffer from one machine to another over the
network. It would be pretty annoying for user-space to have a blacklist
of modifiers that don't work this way.

Example of such user-space:
https://gitlab.freedesktop.org/mstoeckl/waypipe/