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Message-ID: <20250709-debugfs-rust-v9-5-92b9eab5a951@google.com>
Date: Wed, 09 Jul 2025 19:09:32 +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>
Cc: linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
Matthew Maurer <mmaurer@...gle.com>
Subject: [PATCH v9 5/5] rust: samples: Add debugfs sample
Provides an example of using the Rust DebugFS bindings.
Signed-off-by: Matthew Maurer <mmaurer@...gle.com>
---
MAINTAINERS | 1 +
samples/rust/Kconfig | 11 +++
samples/rust/Makefile | 1 +
samples/rust/rust_debugfs.rs | 182 +++++++++++++++++++++++++++++++++++++++++++
4 files changed, 195 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index 1427af9d9779b1f6463409f4392e2900438bdc2a..0d9cb77b54b4608a0e1006ae45761ed7440495ba 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7376,6 +7376,7 @@ F: rust/kernel/devres.rs
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_driver_platform.rs
F: samples/rust/rust_driver_faux.rs
diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
index 7f7371a004ee0a8f67dca99c836596709a70c4fa..01101db41ae31b08a86d048cdd27da8ef9bb23a2 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -62,6 +62,17 @@ config SAMPLE_RUST_DMA
If unsure, say N.
+config SAMPLE_RUST_DEBUGFS
+ tristate "DebugFS Test Module"
+ depends on DEBUG_FS
+ help
+ This option builds the Rust DebugFS Test module sample.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_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 bd2faad63b4f3befe7d1ed5139fe25c7a8b6d7f6..61276222a99f8cc6d7f84c26d0533b30815ebadd 100644
--- a/samples/rust/Makefile
+++ b/samples/rust/Makefile
@@ -4,6 +4,7 @@ ccflags-y += -I$(src) # needed for trace events
obj-$(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_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_debugfs.rs b/samples/rust/rust_debugfs.rs
new file mode 100644
index 0000000000000000000000000000000000000000..21fbf26f7ec07fabad782915046da3cdf52b03b3
--- /dev/null
+++ b/samples/rust/rust_debugfs.rs
@@ -0,0 +1,182 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2025 Google LLC.
+
+//! Sample DebugFS exporting platform driver
+//!
+//! To successfully probe this driver with ACPI, use an ssdt that looks like
+//!
+//! ```dsl
+//! DefinitionBlock ("", "SSDT", 2, "TEST", "VIRTACPI", 0x00000001)
+//!{
+//! Scope (\_SB)
+//! {
+//! Device (T432)
+//! {
+//! Name (_HID, "LNUXDEBF") // ACPI hardware ID to match
+//! Name (_UID, 1)
+//! Name (_STA, 0x0F) // Device present, enabled
+//! Name (_DSD, Package () { // Sample attribute
+//! ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+//! Package() {
+//! Package(2) {"compatible", "sample-debugfs"}
+//! }
+//! })
+//! Name (_CRS, ResourceTemplate ()
+//! {
+//! Memory32Fixed (ReadWrite, 0xFED00000, 0x1000)
+//! })
+//! }
+//! }
+//!}
+//! ```
+
+use core::sync::atomic::AtomicUsize;
+use core::sync::atomic::Ordering;
+use kernel::c_str;
+use kernel::debugfs::{Dir, File};
+use kernel::new_mutex;
+use kernel::prelude::*;
+use kernel::sync::Mutex;
+
+use kernel::{acpi, device::Core, of, platform, str::CString, types::ARef};
+
+kernel::module_platform_driver! {
+ type: Wrapper,
+ name: "rust_debugfs",
+ authors: ["Matthew Maurer"],
+ description: "Rust DebugFS usage sample",
+ license: "GPL",
+}
+
+// This data structure would be unlikely to be there in a real driver - it's to hook up mutation
+// that would normally be driven by whatever the driver was actually servicing and show how that
+// would work. We're assuming here that those methods would have access to a `&RustDebugFs`.
+#[pin_data]
+struct Wrapper {
+ _dir: Dir,
+ #[pin]
+ _wrapped: File<File<RustDebugFs>>,
+}
+
+#[pin_data]
+struct RustDebugFs {
+ pdev: ARef<platform::Device>,
+ // As we only hold these for drop effect (to remove the directory/files) we have a leading
+ // underscore to indicate to the compiler that we don't expect to use this field directly.
+ _debugfs: Dir,
+ #[pin]
+ _compatible: File<CString>,
+ #[pin]
+ counter: File<File<AtomicUsize>>,
+ #[pin]
+ inner: File<Mutex<Inner>>,
+}
+
+#[derive(Debug)]
+struct Inner {
+ x: u32,
+ y: u32,
+}
+
+kernel::of_device_table!(
+ OF_TABLE,
+ MODULE_OF_TABLE,
+ <Wrapper as platform::Driver>::IdInfo,
+ [(of::DeviceId::new(c_str!("test,rust-debugfs-device")), ())]
+);
+
+kernel::acpi_device_table!(
+ ACPI_TABLE,
+ MODULE_ACPI_TABLE,
+ <Wrapper as platform::Driver>::IdInfo,
+ [(acpi::DeviceId::new(c_str!("LNUXDEBF")), ())]
+);
+
+impl platform::Driver for Wrapper {
+ type IdInfo = ();
+ const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
+ const ACPI_ID_TABLE: Option<acpi::IdTable<Self::IdInfo>> = Some(&ACPI_TABLE);
+
+ fn probe(
+ pdev: &platform::Device<Core>,
+ _info: Option<&Self::IdInfo>,
+ ) -> Result<Pin<KBox<Self>>> {
+ KBox::try_pin_init(Wrapper::new(RustDebugFs::new(pdev)), GFP_KERNEL)
+ }
+}
+
+impl Wrapper {
+ /// This builds two debugfs files that would be unusual to exist in the real world to emulate
+ /// actions taken servicing the device. They trigger their action when the debugfs file is
+ /// opened.
+ fn build_control<I: PinInit<RustDebugFs, Error>>(
+ dir: &Dir,
+ init: I,
+ ) -> impl PinInit<File<File<RustDebugFs>>, Error> + use<'_, I> {
+ let swap = dir.fmt_file(c_str!("swap"), init, &|sample, fmt| {
+ let mut guard = sample.inner.lock();
+ let x = guard.x;
+ guard.x = guard.y;
+ guard.y = x;
+ writeln!(fmt, "Swapped!")
+ });
+
+ dir.fmt_file(c_str!("add_counter"), swap, &|sample, fmt| {
+ let mut inner = sample.inner.lock();
+ inner.x += sample.counter.load(Ordering::Relaxed) as u32;
+ writeln!(fmt, "Counter added!")
+ })
+ }
+
+ fn new<I: PinInit<RustDebugFs, Error>>(init: I) -> impl PinInit<Self, Error> + use<I> {
+ let dir = Dir::new(c_str!("sample_control"));
+ try_pin_init! {
+ Self {
+ _wrapped <- Wrapper::build_control(&dir, init),
+ _dir: dir,
+ } ? Error
+ }
+ }
+}
+
+impl RustDebugFs {
+ fn build_counter(dir: &Dir) -> impl PinInit<File<File<AtomicUsize>>> + use<'_> {
+ let counter = dir.fmt_file(c_str!("counter"), AtomicUsize::new(0), &|counter, fmt| {
+ writeln!(fmt, "{}", counter.load(Ordering::Relaxed))
+ });
+ dir.fmt_file(c_str!("inc_counter"), counter, &|counter, fmt| {
+ writeln!(fmt, "{}", counter.fetch_add(1, Ordering::Relaxed))
+ })
+ }
+
+ fn build_inner(dir: &Dir) -> impl PinInit<File<Mutex<Inner>>> + use<'_> {
+ dir.fmt_file(
+ c_str!("pair"),
+ new_mutex!(Inner { x: 3, y: 10 }),
+ &|i, fmt| writeln!(fmt, "{:?}", *i.lock()),
+ )
+ }
+
+ fn new(pdev: &platform::Device<Core>) -> impl PinInit<Self, Error> + use<'_> {
+ let debugfs = Dir::new(c_str!("sample_debugfs"));
+ let dev = pdev.as_ref();
+
+ try_pin_init! {
+ Self {
+ _compatible <- debugfs.fmt_file(
+ c_str!("compatible"),
+ dev.fwnode()
+ .ok_or(ENOENT)?
+ .property_read::<CString>(c_str!("compatible"))
+ .required_by(dev)?,
+ &|cs, w| writeln!(w, "{cs:?}"),
+ ),
+ counter <- Self::build_counter(&debugfs),
+ inner <- Self::build_inner(&debugfs),
+ _debugfs: debugfs,
+ pdev: pdev.into(),
+ }
+ }
+ }
+}
--
2.50.0.727.gbf7dc18ff4-goog
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