Re: [RFC PATCH 0/2] scatterlist rust bindings

[Daniel Almeida <daniel.almeida@collabora.com>]

Hi Abdiel,

> On 12 May 2025, at 06:53, Abdiel Janulgue <abdiel.janulgue@gmail.com> wrote:
> 
> Hi,
> 
> Here are the scatterlist bindings that has been brewing for a while in my
> local tree while working with Nova code. The bindings are used mostly to
> build the radix3 table from the GSP firmware which is loaded via dma.
> This interface can be used on top of existing kernel scatterlist objects
> or to allocate a new one from scratch.
> 
> Some questions still need to be resolved, which mostly come from
> the DeviceSGTable::dma_map() function. Primarily, what if you call
> bindings::dma_map_sgtable() on an already mapped sg_table? From my

Perhaps we should introduce a type for buffers which are known to be mapped. Then
we can simply not offer the option to map for that type.

> experiments it doesn't seem to do anything and no indication is returned if
> the call succeeded or not. Should we save the "mapping info" to a list
> everytime we call DeviceSGTable::dma_map more than once?

What mapping info are you referring to?

> 
> Hoping this initial submission will generate some discussion. I'd like to
> acknowledge valuable feedback from Danilo Krummrich and Lyude
> Paul in shaping this up.
> 
> Abdiel Janulgue (2):
>  rust: add initial scatterlist bindings
>  samples: rust: add sample code for scatterlist bindings
> 
> rust/bindings/bindings_helper.h |   1 +
> rust/helpers/helpers.c          |   1 +
> rust/helpers/scatterlist.c      |  25 +++
> rust/kernel/lib.rs              |   1 +
> rust/kernel/scatterlist.rs      | 275 ++++++++++++++++++++++++++++++++
> samples/rust/rust_dma.rs        |  14 +-
> 6 files changed, 316 insertions(+), 1 deletion(-)
> create mode 100644 rust/helpers/scatterlist.c
> create mode 100644 rust/kernel/scatterlist.rs
> 
> 
> base-commit: dd21715de3dfa6f6457432ce909e5f7eb142a7d2
> -- 
> 2.43.0
> 
> 

— Daniel