Nouveau - Sep 2025 - [PATCH 04/10] gpu: nova-core: Add a slice-buffer (sbuffer) datastructure

On Wed, Aug 27, 2025 at 06:20:01PM +1000, Alistair Popple
wrote:
> From: Joel Fernandes <joelagnelf at nvidia.com>
> 
> A data structure that can be used to write across multiple slices which
> may be out of order in memory. This lets SBuffer user correctly and
> safely write out of memory order, without error-prone tracking of
> pointers/offsets.
> 
>  let mut buf1 = [0u8; 3];
>  let mut buf2 = [0u8; 5];
>  let mut sbuffer = SBuffer::new([&mut buf1[..], &mut buf2[..]]);
> 
>  let data = b"hellowo";
>  let result = sbuffer.write(data);
> 
> An internal conversion of gsp.rs to use this resulted in a nice -ve delta:
> gsp.rs: 37 insertions(+), 99 deletions(-)
> 
> Co-developed-by: Alistair Popple <apopple at nvidia.com>
> Signed-off-by: Alistair Popple <apopple at nvidia.com>
> Signed-off-by: Joel Fernandes <joelagnelf at nvidia.com>
This seems like duplication of the logic in rust/kernel/iov_iter.rs [1].

Alice

[1]: https://lore.kernel.org/r/20250822-iov-iter-v5-0-6ce4819c2977 at google.com

On 2025-09-07 at 20:54 +1000, Alice Ryhl <aliceryhl at google.com>
wrote...
> On Wed, Aug 27, 2025 at 06:20:01PM +1000, Alistair Popple wrote:
> > From: Joel Fernandes <joelagnelf at nvidia.com>
> > 
> > A data structure that can be used to write across multiple slices
which
> > may be out of order in memory. This lets SBuffer user correctly and
> > safely write out of memory order, without error-prone tracking of
> > pointers/offsets.
> > 
> >  let mut buf1 = [0u8; 3];
> >  let mut buf2 = [0u8; 5];
> >  let mut sbuffer = SBuffer::new([&mut buf1[..], &mut
buf2[..]]);
> > 
> >  let data = b"hellowo";
> >  let result = sbuffer.write(data);
> > 
> > An internal conversion of gsp.rs to use this resulted in a nice -ve
delta:
> > gsp.rs: 37 insertions(+), 99 deletions(-)
> > 
> > Co-developed-by: Alistair Popple <apopple at nvidia.com>
> > Signed-off-by: Alistair Popple <apopple at nvidia.com>
> > Signed-off-by: Joel Fernandes <joelagnelf at nvidia.com>
> 
> This seems like duplication of the logic in rust/kernel/iov_iter.rs [1].
Conceptually I guess there is some overlap. The thing that's different here
is we don't have any C version of the iovec struct or iov_iter, and AFAICT
[1]
doesn't provide any way of creating one from within Rust code.
> Alice
> 
> [1]: https://lore.kernel.org/r/20250822-iov-iter-v5-0-6ce4819c2977 at
google.com