On Fri Aug 8, 2025 at 8:56 AM CEST, Sidong Yang wrote:

On Wed, Aug 06, 2025 at 03:38:24PM +0200, Benno Lossin wrote:

quoted

On Wed Aug 6, 2025 at 2:38 PM CEST, Daniel Almeida wrote:

quoted

Hi Benno,

quoted

On 2 Aug 2025, at 07:52, Benno Lossin [off-list ref] wrote:

On Fri Aug 1, 2025 at 3:48 PM CEST, Daniel Almeida wrote:

quoted

quoted

On 27 Jul 2025, at 12:03, Sidong Yang [off-list ref] wrote:
+    #[inline]
+    pub fn pdu(&mut self) -> &mut MaybeUninit<[u8; 32]> {

Why MaybeUninit? Also, this is a question for others, but I don´t think
that `u8`s can ever be uninitialized as all byte values are valid for `u8`.

`u8` can be uninitialized. Uninitialized doesn't just mean "can take any
bit pattern", but also "is known to the compiler as being
uninitialized". The docs of `MaybeUninit` explain it like this:

   Moreover, uninitialized memory is special in that it does not have a
   fixed value ("fixed" meaning "it won´t change without being written
   to"). Reading the same uninitialized byte multiple times can give
   different results.

But the return type probably should be `&mut [MaybeUninit<u8>; 32]`
instead.

Right, but I guess the question then is why would we ever need to use
MaybeUninit here anyways.

It's a reference to a C array. Just treat that as initialized.

AFAIK C uninitialized memory also is considered uninitialized in Rust.
So if this array is not properly initialized on the C side, this would
be the correct type. If it is initialized, then just use `&mut [u8; 32]`.

pdu field is memory chunk for driver can use it freely. The driver usually
saves a private data and read or modify it on the other context. using
just `&mut [u8;32]` would be simple and easy to use.

Private data is usually handled using `ForeignOwnable` in Rust. What
kind of data would be stored there? If it's a pointer, then `&mut [u8;
32]` would not be the correct choice.

---
Cheers,
Benno