linux-kernel - Re: [PATCH -next v7 1/2] rust: clist: Add support to interface with C linked lists

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Message-ID: <8dde5b79-29d6-4840-be9a-31bc4af27cf9@nvidia.com>
Date: Fri, 6 Feb 2026 15:46:31 -0500
From: Joel Fernandes <joelagnelf@...dia.com>
To: Daniel Almeida <daniel.almeida@...labora.com>
Cc: linux-kernel@...r.kernel.org,
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Subject: Re: [PATCH -next v7 1/2] rust: clist: Add support to interface with C
 linked lists

On 2/6/2026 12:49 PM, Daniel Almeida wrote:
>> +#[repr(transparent)]
>> +pub(crate) struct CList<T, const OFFSET: usize>(CListHead, PhantomData<T>);
>> +
>> +impl<T, const OFFSET: usize> CList<T, OFFSET> {
>> +    /// Create a typed [`CList`] reference from a raw sentinel `list_head` pointer.
>> +    ///
>> +    /// # Safety
>> +    ///
>> +    /// - `ptr` must be a valid pointer to an allocated and initialized `list_head` structure
>> +    ///   representing a list sentinel.
>> +    /// - `ptr` must remain valid and unmodified for the lifetime `'a`.
>> +    /// - The list must contain items where the `list_head` field is at byte offset `OFFSET`.
>> +    /// - `T` must be `#[repr(transparent)]` over the C struct.
>> +    #[inline]
>> +    pub(crate) unsafe fn from_raw<'a>(ptr: *mut bindings::list_head) -> &'a Self {
>> +        // SAFETY:
>> +        // - [`CList`] has same layout as [`CListHead`] due to repr(transparent).
>> +        // - Caller guarantees `ptr` is a valid, sentinel `list_head` object.
>> +        unsafe { &*ptr.cast() }
>> +    }
>> +
>> +    /// Check if the list is empty.
>> +    #[inline]
>> +    #[expect(dead_code)]
>> +    pub(crate) fn is_empty(&self) -> bool {
>
> Why can’t this be pub?

I believe this was suggested by Gary. See the other thread where we are
discussing it (with Gary and Danilo) and let us discuss there.

-- 
Joel Fernandes