On Thu Sep 4, 2025 at 5:16 AM CEST, Alexandre Courbot wrote:
> On Thu Sep 4, 2025 at 12:15 AM JST, Joel Fernandes wrote:
> <snip>
>>>> +use kernel::prelude::*;
>>>> +
>>>> +/// Macro for defining bitfield-packed structures in Rust.
>>>> +/// The size of the underlying storage type is specified with
>>>> #[repr(TYPE)].
>>>> +///
>>>> +/// # Example (just for illustration)
>>>> +/// ```rust
>>>> +/// bitstruct! {
>>>> +/// #[repr(u64)]
>>>> +/// pub struct PageTableEntry {
>>>> +/// 0:0 present as bool,
>>>> +/// 1:1 writable as bool,
>>>> +/// 11:9 available as u8,
>>>> +/// 51:12 pfn as u64,
>>>> +/// 62:52 available2 as u16,
>>>> +/// 63:63 nx as bool,
>>>
>>> A note on syntax: for nova-core, we may want to use the `H:L` notation,
>>> as this is what OpenRM uses, but in the larger kernel we might want to
>>> use inclusive ranges (`L..=H`) as it will look more natural in Rust
>>> code (and is the notation the `bits` module already uses).
>>
>> Perhaps future add-on enhancement to have both syntax? I'd like to initially
>> keep H:L and stabilize the code first, what do you think?
>
> Let's have the discussion with the other stakeholders (Daniel?). I think
> in Nova we want to keep the `H:L` syntax, as it matches what the OpenRM
> headers do (so Nova would have its own `register` macro that calls into
> the common one, tweaking things as it needs). But in the kernel crate we
> should use something intuitive for everyone.
I don't care too much about whether it's gonna be H:L or L:H [1], but I do care
about being consistent throughout the kernel. Let's not start the practice of
twisting kernel APIs to NV_* specific APIs that differ from what people are used
to work with in the kernel.
[1] If it's gonna be H:L, I think we should also list things in reverse order,
i.e.:
pub struct PageTableEntry {
63:63 nx as bool,
62:52 available2 as u16,
51:12 pfn as u64,
11:9 available as u8,
1:1 writable as bool,
0:0 present as bool,
}
This is also what would be my preferred style for the kernel in general.
- Danilo
