linux-kernel - Re: [PATCH 6/7] rust: debugfs: support binary large objects for ScopedDir

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Message-Id: <DDKON3JTFU2F.LN0UZ1ZKWNFV@kernel.org>
Date: Fri, 17 Oct 2025 16:55:25 +0200
From: "Danilo Krummrich" <dakr@...nel.org>
To: "Alice Ryhl" <aliceryhl@...gle.com>
Cc: <gregkh@...uxfoundation.org>, <rafael@...nel.org>, <ojeda@...nel.org>,
 <alex.gaynor@...il.com>, <boqun.feng@...il.com>, <gary@...yguo.net>,
 <bjorn3_gh@...tonmail.com>, <lossin@...nel.org>, <a.hindborg@...nel.org>,
 <tmgross@...ch.edu>, <mmaurer@...gle.com>,
 <rust-for-linux@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/7] rust: debugfs: support binary large objects for
 ScopedDir

On Fri Oct 17, 2025 at 3:00 PM CEST, Alice Ryhl wrote:
> On Sat, Oct 04, 2025 at 12:26:43AM +0200, Danilo Krummrich wrote:
>> Add support for creating binary debugfs files via ScopedDir. This
>> mirrors the existing functionality for Dir, but without producing an
>> owning handle -- files are automatically removed when the associated
>> Scope is dropped.
>> 
>> Signed-off-by: Danilo Krummrich <dakr@...nel.org>
>> ---
>>  rust/kernel/debugfs.rs | 45 ++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 45 insertions(+)
>> 
>> diff --git a/rust/kernel/debugfs.rs b/rust/kernel/debugfs.rs
>> index 3c3bbcc126ef..0eb1719e4953 100644
>> --- a/rust/kernel/debugfs.rs
>> +++ b/rust/kernel/debugfs.rs
>> @@ -531,6 +531,20 @@ pub fn read_only_file<T: Writer + Send + Sync + 'static>(&self, name: &CStr, dat
>>          self.create_file(name, data, &T::FILE_OPS)
>>      }
>>  
>> +    /// Creates a read-only binary file in this directory.
>> +    ///
>> +    /// The file's contents are produced by invoking [`BinaryWriter::write_to_slice`].
>> +    ///
>> +    /// This function does not produce an owning handle to the file. The created file is removed
>> +    /// when the [`Scope`] that this directory belongs to is dropped.
>> +    pub fn read_binary_file<T: BinaryWriter + Send + Sync + 'static>(
>> +        &self,
>> +        name: &CStr,
>> +        data: &'data T,
>> +    ) {
>> +        self.create_file(name, data, &T::FILE_OPS)
>
> Why isn't <T as MyTrait> need here when it's needed for the other
> methods?

It's not needed for write_binary_file() I think, but read_write_binary_file()
needs it because:

	fn read_write_binary_file<T: BinaryWriter + BinaryReader + Send + Sync + 'static>()

So, just &T::FILE_OPS is ambiguous, because it implements BinaryReadFile,
BinaryWriteFile and BinaryReadWriteFile.