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Message-ID: <20250501-debugfs-rust-v3-4-850869fab672@google.com>
Date: Thu, 01 May 2025 22:47:44 +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>, Benno Lossin <benno.lossin@...ton.me>,
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>
Cc: linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
Matthew Maurer <mmaurer@...gle.com>
Subject: [PATCH v3 4/4] 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 | 54 ++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 67 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index a3b835e427b083a4ddd690d9e7739851f0af47ae..426bcdac025134e20911de8e2cf5c9efb0591814 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7278,6 +7278,7 @@ 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 43cb72d72631bb2d6e06185e1d88778edff6ee13..6c42ed73f842cda26256039e6917bb443738d3f1 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -51,6 +51,17 @@ config SAMPLE_RUST_DMA
If unsure, say N.
+config SAMPLE_RUST_DEBUGFS
+ tristate "DebugFS Test Driver"
+ depends on DEBUG_FS
+ help
+ This option builds the Rust DebugFS Test driver 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 6a466afd2a21eba84a3b7b2be29f25dce44e9053..b1fc4677ed53fcf7d0f5a3dbf322f65851bc1784 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..b22255667f3bb91b10555ac8b91be850cd5f172e
--- /dev/null
+++ b/samples/rust/rust_debugfs.rs
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2025 Google LLC.
+
+//! Sample DebugFS exporting module
+
+use core::sync::atomic::{AtomicU32, Ordering};
+use kernel::c_str;
+use kernel::debugfs::Dir;
+use kernel::prelude::*;
+
+module! {
+ type: RustDebugFs,
+ name: "rust_debugfs",
+ authors: ["Matthew Maurer"],
+ description: "Rust DebugFS usage sample",
+ license: "GPL",
+}
+
+struct RustDebugFs {
+ // As we only hold this for drop effect (to remove the directory) we have a leading underscore
+ // to indicate to the compiler that we don't expect to use this field directly.
+ _debugfs: Dir,
+}
+
+static EXAMPLE: AtomicU32 = AtomicU32::new(8);
+
+impl kernel::Module for RustDebugFs {
+ fn init(_this: &'static ThisModule) -> Result<Self> {
+ // Create a debugfs directory in the root of the filesystem called "sample_debugfs".
+ let debugfs = Dir::new(c_str!("sample_debugfs"));
+
+ // Create a subdirectory, so "sample_debugfs/subdir" now exists.
+ let sub = debugfs.subdir(c_str!("subdir"));
+
+ // Create a single file in the subdirectory called "example" that will read from the
+ // `EXAMPLE` atomic variable.
+ sub.fmt_file(c_str!("example"), &EXAMPLE, &|example, f| {
+ writeln!(f, "Reading atomic: {}", example.load(Ordering::Relaxed))
+ });
+ // Now, "sample_debugfs/subdir/example" will print "Reading atomic: 8\n" when read.
+
+ // Change the value in the variable displayed by the file. This is intended to demonstrate
+ // that the module can continue to change the value used by the file.
+ EXAMPLE.store(10, Ordering::Relaxed);
+ // Now, "sample_debugfs/subdir/example" will print "Reading atomic: 10\n" when read.
+
+ // Save the root debugfs directory we created to our module object. It will be
+ // automatically cleaned up when our module is unloaded because dropping the module object
+ // will drop the `Dir` handle. The base directory, the subdirectory, and the file will all
+ // continue to exist until the module is unloaded.
+ Ok(Self { _debugfs: debugfs })
+ }
+}
--
2.49.0.906.g1f30a19c02-goog
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