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Message-ID: <20250819-debugfs-rust-v10-7-86e20f3cf3bb@google.com>
Date: Tue, 19 Aug 2025 22:53:42 +0000
From: Matthew Maurer <mmaurer@...gle.com>
To: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Andreas Hindborg <a.hindborg@...nel.org>,
Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
Danilo Krummrich <dakr@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>,
Timur Tabi <ttabi@...dia.com>, Benno Lossin <lossin@...nel.org>,
Dirk Beheme <dirk.behme@...bosch.com>
Cc: linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
Matthew Maurer <mmaurer@...gle.com>
Subject: [PATCH v10 7/7] samples: rust: Add scoped debugfs sample driver
Adds a new sample driver `rust_scoped_debugfs` that demonstrates the
use of the scoped debugfs APIs.
The driver creates a `control` directory with two write-only files,
`create` and `remove`. Writing a name and a series of numbers to
`create` will create a new subdirectory under a `dynamic` directory.
This new subdirectory will contain files that expose the numbers as
atomic values.
Writing a name to `remove` will remove the corresponding subdirectory
from the `dynamic` directory.
This sample serves as an example of how to use the `debugfs::Scope`
and `debugfs::ScopedDir` APIs to create and manage debugfs entries
that are tied to the lifetime of a data structure.
Signed-off-by: Matthew Maurer <mmaurer@...gle.com>
---
MAINTAINERS | 1 +
samples/rust/Kconfig | 11 +++
samples/rust/Makefile | 1 +
samples/rust/rust_scoped_debugfs.rs | 134 ++++++++++++++++++++++++++++++++++++
4 files changed, 147 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index 5b6db584a33dd7ee39de3fdd0085d2bd7b7bef0e..2cbe890085dbb6a652623b38dd0eadeeaa127a94 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7482,6 +7482,7 @@ F: rust/kernel/driver.rs
F: rust/kernel/faux.rs
F: rust/kernel/platform.rs
F: samples/rust/rust_debugfs.rs
+F: samples/rust/rust_scoped_debugfs.rs
F: samples/rust/rust_driver_platform.rs
F: samples/rust/rust_driver_faux.rs
diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
index 01101db41ae31b08a86d048cdd27da8ef9bb23a2..3372935519d658529ee7ba25fb2c3fff6adae8c4 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -73,6 +73,17 @@ config SAMPLE_RUST_DEBUGFS
If unsure, say N.
+config SAMPLE_RUST_SCOPED_DEBUGFS
+ tristate "Scoped DebugFS Test Module"
+ depends on DEBUG_FS
+ help
+ This option builds the Rust Scoped DebugFS Test module sample.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_scoped_debugfs.
+
+ If unsure, say N.
+
config SAMPLE_RUST_DRIVER_PCI
tristate "PCI Driver"
depends on PCI
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
index 61276222a99f8cc6d7f84c26d0533b30815ebadd..de10b7f4db3996dc57be813ceb076d050ad8f65a 100644
--- a/samples/rust/Makefile
+++ b/samples/rust/Makefile
@@ -5,6 +5,7 @@ obj-$(CONFIG_SAMPLE_RUST_MINIMAL) += rust_minimal.o
obj-$(CONFIG_SAMPLE_RUST_MISC_DEVICE) += rust_misc_device.o
obj-$(CONFIG_SAMPLE_RUST_PRINT) += rust_print.o
obj-$(CONFIG_SAMPLE_RUST_DEBUGFS) += rust_debugfs.o
+obj-$(CONFIG_SAMPLE_RUST_SCOPED_DEBUGFS) += rust_scoped_debugfs.o
obj-$(CONFIG_SAMPLE_RUST_DMA) += rust_dma.o
obj-$(CONFIG_SAMPLE_RUST_DRIVER_PCI) += rust_driver_pci.o
obj-$(CONFIG_SAMPLE_RUST_DRIVER_PLATFORM) += rust_driver_platform.o
diff --git a/samples/rust/rust_scoped_debugfs.rs b/samples/rust/rust_scoped_debugfs.rs
new file mode 100644
index 0000000000000000000000000000000000000000..7c34cab62a2753d1ede3a1334be1fb13ddce780c
--- /dev/null
+++ b/samples/rust/rust_scoped_debugfs.rs
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2025 Google LLC.
+
+//! Sample DebugFS exporting platform driver that demonstrates the use of
+//! `Scope::dir` to create a variety of files without the need to separately
+//! track them all.
+
+use core::sync::atomic::AtomicUsize;
+use kernel::debugfs::{Dir, Scope};
+use kernel::prelude::*;
+use kernel::sync::Mutex;
+use kernel::{c_str, new_mutex, str::CString};
+
+module! {
+ type: RustScopedDebugFs,
+ name: "rust_scoped_debugfs",
+ authors: ["Matthew Maurer"],
+ description: "Rust Scoped DebugFS usage sample",
+ license: "GPL",
+}
+
+fn remove_file_write(
+ mod_data: &ModuleData,
+ reader: &mut kernel::uaccess::UserSliceReader,
+) -> Result<()> {
+ let mut buf = [0u8; 128];
+ if reader.len() >= buf.len() {
+ return Err(EINVAL);
+ }
+ let n = reader.len();
+ reader.read_slice(&mut buf[..n])?;
+
+ let s = core::str::from_utf8(&buf[..n]).map_err(|_| EINVAL)?.trim();
+ let nul_idx = s.len();
+ buf[nul_idx] = 0;
+ let to_remove = CStr::from_bytes_with_nul(&buf[..nul_idx + 1]).map_err(|_| EINVAL)?;
+ mod_data
+ .devices
+ .lock()
+ .retain(|device| device.name.as_bytes() != to_remove.as_bytes());
+ Ok(())
+}
+
+fn create_file_write(
+ mod_data: &ModuleData,
+ reader: &mut kernel::uaccess::UserSliceReader,
+) -> Result<()> {
+ let mut buf = [0u8; 128];
+ if reader.len() > buf.len() {
+ return Err(EINVAL);
+ }
+ let n = reader.len();
+ reader.read_slice(&mut buf[..n])?;
+
+ let mut nums = KVec::new();
+
+ let s = core::str::from_utf8(&buf[..n]).map_err(|_| EINVAL)?.trim();
+ let mut items = s.split_whitespace();
+ let name_str = items.next().ok_or(EINVAL)?;
+ let name = CString::try_from_fmt(fmt!("{name_str}"))?;
+ let file_name = CString::try_from_fmt(fmt!("{name_str}"))?;
+ for sub in items {
+ nums.push(
+ AtomicUsize::new(sub.parse().map_err(|_| EINVAL)?),
+ GFP_KERNEL,
+ )?;
+ }
+
+ let scope = KBox::pin_init(
+ mod_data
+ .device_dir
+ .scope(DeviceData { name, nums }, &file_name, |dev_data, dir| {
+ for (idx, val) in dev_data.nums.iter().enumerate() {
+ let Ok(name) = CString::try_from_fmt(fmt!("{idx}")) else {
+ return;
+ };
+ dir.read_write_file(&name, val);
+ }
+ }),
+ GFP_KERNEL,
+ )?;
+ (*mod_data.devices.lock()).push(scope, GFP_KERNEL)?;
+
+ Ok(())
+}
+
+struct RustScopedDebugFs {
+ _data: Pin<KBox<Scope<ModuleData>>>,
+}
+
+#[pin_data]
+struct ModuleData {
+ device_dir: Dir,
+ #[pin]
+ devices: Mutex<KVec<Pin<KBox<Scope<DeviceData>>>>>,
+}
+
+impl ModuleData {
+ fn init(device_dir: Dir) -> impl PinInit<Self> {
+ pin_init! {
+ Self {
+ device_dir: device_dir,
+ devices <- new_mutex!(KVec::new())
+ }
+ }
+ }
+}
+
+struct DeviceData {
+ name: CString,
+ nums: KVec<AtomicUsize>,
+}
+
+fn init_control(base_dir: &Dir, dyn_dirs: Dir) -> impl PinInit<Scope<ModuleData>> + '_ {
+ base_dir.scope(
+ ModuleData::init(dyn_dirs),
+ c_str!("control"),
+ |data, dir| {
+ dir.write_only_callback_file(c_str!("create"), data, &create_file_write);
+ dir.write_only_callback_file(c_str!("remove"), data, &remove_file_write);
+ },
+ )
+}
+
+impl kernel::Module for RustScopedDebugFs {
+ fn init(_module: &'static kernel::ThisModule) -> Result<Self, Error> {
+ let base_dir = Dir::new(c_str!("rust_scoped_debugfs"));
+ let dyn_dirs = base_dir.subdir(c_str!("dynamic"));
+ Ok(Self {
+ _data: KBox::pin_init(init_control(&base_dir, dyn_dirs), GFP_KERNEL)?,
+ })
+ }
+}
--
2.51.0.rc1.167.g924127e9c0-goog
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