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Wysocki" , Sami Tolvanen , Timur Tabi Cc: linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, Matthew Maurer Content-Type: text/plain; charset="utf-8" Provides an example of using the Rust DebugFS bindings. Signed-off-by: Matthew Maurer --- MAINTAINERS | 1 + samples/rust/Kconfig | 11 ++++++++ samples/rust/Makefile | 1 + samples/rust/rust_debugfs.rs | 60 ++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 73 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..a4b17c8241330b2f6caf8f17a5b2366138de6ced --- /dev/null +++ b/samples/rust/rust_debugfs.rs @@ -0,0 +1,60 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Copyright (C) 2025 Google LLC. + +//! Sample DebugFS exporting module + +use core::mem::{forget, ManuallyDrop}; +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>, +} + +static EXAMPLE: AtomicU32 = AtomicU32::new(8); + +impl kernel::Module for RustDebugFs { + fn init(_this: &'static ThisModule) -> Result { + // 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. + // We wrap it in `ManuallyDrop` so that the subdirectory is not automatically discarded + // at the end of the scope - it will be cleaned up when `debugfs` is. + let sub = ManuallyDrop::new(debugfs.subdir(c_str!("subdir"))); + + // Create a single file in the subdirectory called "example" that will read from the + // `EXAMPLE` atomic variable. + // We `forget` the result to avoid deleting the file at the end of the scope. + forget(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 }) + } +} -- 2.49.0.967.g6a0df3ecc3-goog