rust: debugfs: Add support for writable files

Extends the `debugfs` API to support creating writable files. This
is done via the `Dir::write_only_file` and `Dir::read_write_file`
methods, which take a data object that implements the `Reader`
trait.

Signed-off-by: Matthew Maurer <mmaurer@google.com>
Tested-by: Dirk Behme <dirk.behme@de.bosch.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20250904-debugfs-rust-v11-3-7d12a165685a@google.com
[ Fix up Result<()> -> Result. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 35 insertions, 2 deletions

diff --git a/rust/kernel/debugfs.rs b/rust/kernel/debugfs.rs
index 988aacdadbfa..5d77e0cd393c 100644
--- a/rust/kernel/debugfs.rs
+++ b/rust/kernel/debugfs.rs
@@ -16,10 +16,10 @@ use core::marker::PhantomPinned;
 use core::ops::Deref;
 
 mod traits;
-pub use traits::Writer;
+pub use traits::{Reader, Writer};
 
 mod file_ops;
-use file_ops::{FileOps, ReadFile};
+use file_ops::{FileOps, ReadFile, ReadWriteFile, WriteFile};
 #[cfg(CONFIG_DEBUG_FS)]
 mod entry;
 #[cfg(CONFIG_DEBUG_FS)]
@@ -142,6 +142,39 @@ impl Dir {
         let file_ops = &<T as ReadFile<_>>::FILE_OPS;
         self.create_file(name, data, file_ops)
     }
+
+    /// Creates a read-write file in this directory.
+    ///
+    /// Reading the file uses the [`Writer`] implementation.
+    /// Writing to the file uses the [`Reader`] implementation.
+    pub fn read_write_file<'a, T, E: 'a>(
+        &'a self,
+        name: &'a CStr,
+        data: impl PinInit<T, E> + 'a,
+    ) -> impl PinInit<File<T>, E> + 'a
+    where
+        T: Writer + Reader + Send + Sync + 'static,
+    {
+        let file_ops = &<T as ReadWriteFile<_>>::FILE_OPS;
+        self.create_file(name, data, file_ops)
+    }
+
+    /// Creates a write-only file in this directory.
+    ///
+    /// The file owns its backing data. Writing to the file uses the [`Reader`]
+    /// implementation.
+    ///
+    /// The file is removed when the returned [`File`] is dropped.
+    pub fn write_only_file<'a, T, E: 'a>(
+        &'a self,
+        name: &'a CStr,
+        data: impl PinInit<T, E> + 'a,
+    ) -> impl PinInit<File<T>, E> + 'a
+    where
+        T: Reader + Send + Sync + 'static,
+    {
+        self.create_file(name, data, &T::FILE_OPS)
+    }
 }
 
 #[pin_data]