Re: [PATCH v2 4/8] rust: debugfs: support for binary large objects

["Alexandre Courbot" <acourbot@nvidia.com>]

On Tue Oct 21, 2025 at 7:26 AM JST, Danilo Krummrich wrote:
<snip>
> @@ -65,8 +66,8 @@ fn deref(&self) -> &Self::Target {
>  
>  struct WriterAdapter<T>(T);
>  
> -impl<'a, T: Writer> Display for WriterAdapter<&'a T> {
> -    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
> +impl<'a, T: Writer> fmt::Display for WriterAdapter<&'a T> {
> +    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
>          self.0.write(f)
>      }
>  }
> @@ -245,3 +246,139 @@ impl<T: Reader + Sync> WriteFile<T> for T {
>          unsafe { FileOps::new(operations, 0o200) }
>      };
>  }
> +
> +extern "C" fn blob_read<T: BinaryWriter>(
> +    file: *mut bindings::file,
> +    buf: *mut c_char,
> +    count: usize,
> +    ppos: *mut file::Offset,
> +) -> isize {
> +    // SAFETY:
> +    // - `file` is a valid pointer to a `struct file`.
> +    // - The type invariant of `FileOps` guarantees that `private_data` points to a valid `T`.
> +    let this = unsafe { &*((*file).private_data.cast::<T>()) };
> +
> +    // SAFETY: `ppos` is a valid `file::Offset` pointer.
> +    let pos = unsafe { &mut *ppos };
> +
> +    let mut writer = UserSlice::new(UserPtr::from_ptr(buf.cast()), count).writer();
> +
> +    let ret = || -> Result<isize> {
> +        let offset = *pos;
> +
> +        let written = this.write_to_slice(&mut writer, offset)?;
> +        *pos = offset.saturating_add(file::Offset::try_from(written)?);
> +
> +        Ok(written.try_into()?)
> +    }();
> +
> +    match ret {
> +        Ok(n) => n,
> +        Err(e) => e.to_errno() as isize,
> +    }
> +}
> +
> +pub(crate) trait BinaryReadFile<T> {

I know this trait is crate-local, but having a short documentation for
it would be helpful for first-time readers like myself. :)