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Message-ID: <20250918144356.28585-4-manerakai@protonmail.com>
Date: Thu, 18 Sep 2025 14:45:44 +0000
From: ManeraKai <manerakai@...tonmail.com>
To: "aliceryhl@...gle.com" <aliceryhl@...gle.com>, "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>, "arnd@...db.de" <arnd@...db.de>
Cc: "rust-for-linux@...r.kernel.org" <rust-for-linux@...r.kernel.org>, "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "manerakai@...tonmail.com" <manerakai@...tonmail.com>
Subject: [PATCH 3/3] samples: rust: Updated the example using the Rust MiscDevice abstraction
This sample driver will now:
- use the new general `FileOperations` abstraction.
- have `read` and `write` methods, that use a persistent kernel buffer to
store data.
Signed-off-by: ManeraKai <manerakai@...tonmail.com>
---
samples/rust/rust_misc_device.rs | 283 +++++++++++++++++++++----------
1 file changed, 195 insertions(+), 88 deletions(-)
diff --git a/samples/rust/rust_misc_device.rs b/samples/rust/rust_misc_device.rs
index d052294cebb8..c8e90eb9b9ad 100644
--- a/samples/rust/rust_misc_device.rs
+++ b/samples/rust/rust_misc_device.rs
@@ -7,92 +7,139 @@
//! Below is an example userspace C program that exercises this sample's functionality.
//!
//! ```c
-//! #include <stdio.h>
-//! #include <stdlib.h>
-//! #include <errno.h>
-//! #include <fcntl.h>
-//! #include <unistd.h>
-//! #include <sys/ioctl.h>
-//!
-//! #define RUST_MISC_DEV_FAIL _IO('|', 0)
-//! #define RUST_MISC_DEV_HELLO _IO('|', 0x80)
-//! #define RUST_MISC_DEV_GET_VALUE _IOR('|', 0x81, int)
-//! #define RUST_MISC_DEV_SET_VALUE _IOW('|', 0x82, int)
-//!
-//! int main() {
-//! int value, new_value;
-//! int fd, ret;
-//!
-//! // Open the device file
-//! printf("Opening /dev/rust-misc-device for reading and writing\n");
-//! fd = open("/dev/rust-misc-device", O_RDWR);
-//! if (fd < 0) {
-//! perror("open");
-//! return errno;
-//! }
-//!
-//! // Make call into driver to say "hello"
-//! printf("Calling Hello\n");
-//! ret = ioctl(fd, RUST_MISC_DEV_HELLO, NULL);
-//! if (ret < 0) {
-//! perror("ioctl: Failed to call into Hello");
-//! close(fd);
-//! return errno;
-//! }
-//!
-//! // Get initial value
-//! printf("Fetching initial value\n");
-//! ret = ioctl(fd, RUST_MISC_DEV_GET_VALUE, &value);
-//! if (ret < 0) {
-//! perror("ioctl: Failed to fetch the initial value");
-//! close(fd);
-//! return errno;
-//! }
-//!
-//! value++;
-//!
-//! // Set value to something different
-//! printf("Submitting new value (%d)\n", value);
-//! ret = ioctl(fd, RUST_MISC_DEV_SET_VALUE, &value);
-//! if (ret < 0) {
-//! perror("ioctl: Failed to submit new value");
-//! close(fd);
-//! return errno;
-//! }
-//!
-//! // Ensure new value was applied
-//! printf("Fetching new value\n");
-//! ret = ioctl(fd, RUST_MISC_DEV_GET_VALUE, &new_value);
-//! if (ret < 0) {
-//! perror("ioctl: Failed to fetch the new value");
-//! close(fd);
-//! return errno;
-//! }
-//!
-//! if (value != new_value) {
-//! printf("Failed: Committed and retrieved values are different (%d - %d)\n", value, new_value);
-//! close(fd);
-//! return -1;
-//! }
-//!
-//! // Call the unsuccessful ioctl
-//! printf("Attempting to call in to an non-existent IOCTL\n");
-//! ret = ioctl(fd, RUST_MISC_DEV_FAIL, NULL);
-//! if (ret < 0) {
-//! perror("ioctl: Succeeded to fail - this was expected");
-//! } else {
-//! printf("ioctl: Failed to fail\n");
-//! close(fd);
-//! return -1;
-//! }
-//!
-//! // Close the device file
-//! printf("Closing /dev/rust-misc-device\n");
-//! close(fd);
-//!
-//! printf("Success\n");
-//! return 0;
-//! }
+//!#include <errno.h>
+//!#include <fcntl.h>
+//!#include <stdint.h>
+//!#include <stdio.h>
+//!#include <stdlib.h>
+//!#include <sys/ioctl.h>
+//!#include <unistd.h>
+//!
+//!#define RUST_MISC_DEV_FAIL _IO('|', 0)
+//!#define RUST_MISC_DEV_HELLO _IO('|', 0x80)
+//!#define RUST_MISC_DEV_GET_VALUE _IOR('|', 0x81, int)
+//!#define RUST_MISC_DEV_SET_VALUE _IOW('|', 0x82, int)
+//!
+//!int main() {
+//! int value, new_value;
+//! int fd, ret;
+//!
+//! // Open the device file
+//! printf("Opening /dev/rust-misc-device for reading and writing\n");
+//! fd = open("/dev/rust-misc-device", O_RDWR);
+//! if (fd < 0) {
+//! perror("open");
+//! return errno;
+//! }
+//!
+//! // Make call into driver to say "hello"
+//! printf("Calling Hello\n");
+//! ret = ioctl(fd, RUST_MISC_DEV_HELLO, NULL);
+//! if (ret < 0) {
+//! perror("ioctl: Failed to call into Hello");
+//! close(fd);
+//! return errno;
+//! }
+//!
+//! // Get initial value
+//! printf("Fetching initial value\n");
+//! ret = ioctl(fd, RUST_MISC_DEV_GET_VALUE, &value);
+//! if (ret < 0) {
+//! perror("ioctl: Failed to fetch the initial value");
+//! close(fd);
+//! return errno;
+//! }
+//!
+//! value++;
+//!
+//! // Set value to something different
+//! printf("Submitting new value (%d)\n", value);
+//! ret = ioctl(fd, RUST_MISC_DEV_SET_VALUE, &value);
+//! if (ret < 0) {
+//! perror("ioctl: Failed to submit new value");
+//! close(fd);
+//! return errno;
+//! }
+//!
+//! // Ensure new value was applied
+//! printf("Fetching new value\n");
+//! ret = ioctl(fd, RUST_MISC_DEV_GET_VALUE, &new_value);
+//! if (ret < 0) {
+//! perror("ioctl: Failed to fetch the new value");
+//! close(fd);
+//! return errno;
+//! }
+//!
+//! if (value != new_value) {
+//! printf("Failed: Committed and retrieved values are different (%d -%d)\n",
+//! value, new_value);
+//! close(fd);
+//! return -1;
+//! }
+//!
+//! // Call the unsuccessful ioctl
+//! printf("Attempting to call in to an non-existent IOCTL\n");
+//! ret = ioctl(fd, RUST_MISC_DEV_FAIL, NULL);
+//! if (ret < 0) {
+//! perror("ioctl: Succeeded to fail - this was expected");
+//! } else {
+//! printf("ioctl: Failed to fail\n");
+//! close(fd);
+//! return -1;
+//! }
+//!
+//! ssize_t bytes_written;
+//!
+//! // Write
+//! char str1[] = {'H', 'e', 'l', 'l', 'o', '\0'};
+//! printf("Attempting to write to the file\n");
+//! bytes_written = write(fd, str1, sizeof(str1) * sizeof(uint8_t));
+//! if (bytes_written < 0) {
+//! perror("Error writing to file");
+//! close(fd);
+//! return 1;
+//! }
+//!
+//! // Write with a custom offset
+//! printf("Attempting to write to the file with a custom offset\n");
+//! char str2[] = {'i', ',', ' ', 'w', 'o', 'r', 'l', 'd', '!', '\0'};
+//! // bytes_written = write(fd, str2, sizeof(str2) * sizeof(uint8_t));
+//! bytes_written = pwrite(fd, str2, sizeof(str2), 1);
+//! if (bytes_written < 0) {
+//! perror("Error writing to file 2");
+//! close(fd);
+//! return 1;
+//! }
+//!
+//! // Read
+//! printf("Attempting to read from the file\n");
+//! char buffer1[20];
+//! ssize_t readCount1 = pread(fd, buffer1, sizeof(buffer1), 0);
+//! if (readCount1 < 0) {
+//! perror("Error reading from file\n");
+//! close(fd);
+//! return errno;
+//! }
+//! printf("Data: \"%s\n\"", buffer1);
+//!
+//! // Read with a custom offset
+//! printf("Attempting to read from the file with a custom offset\n");
+//! char buffer2[20];
+//! ssize_t readCount2 = pread(fd, buffer2, sizeof(buffer2), 4);
+//! if (readCount2 < 0) {
+//! perror("Error reading from file\n");
+//! close(fd);
+//! return errno;
+//! }
+//! printf("Data: \"%s\n\"", buffer2);
+//!
+//! // Close the device file
+//! printf("Closing /dev/rust-misc-device\n");
+//! close(fd);
+//!
+//! printf("Success\n");
+//! return 0;
+//!}
//! ```
use core::pin::Pin;
@@ -101,12 +148,13 @@
c_str,
device::Device,
fs::{file_operations::FileOperations, File},
+ global_lock,
ioctl::{_IO, _IOC_SIZE, _IOR, _IOW},
miscdevice::{MiscDeviceOptions, MiscDeviceRegistration},
new_mutex,
prelude::*,
sync::Mutex,
- types::ARef,
+ types::{ARef, ForeignOwnable},
uaccess::{UserSlice, UserSliceReader, UserSliceWriter},
};
@@ -128,6 +176,11 @@ struct RustMiscDeviceModule {
_miscdev: MiscDeviceRegistration<RustMiscDevice>,
}
+global_lock! {
+ // SAFETY: Initialized in module initializer before first use.
+ unsafe(uninit) static DATA: Mutex<KVec<u8>> = KVec::new();
+}
+
impl kernel::InPlaceModule for RustMiscDeviceModule {
fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
pr_info!("Initialising Rust Misc Device Sample\n");
@@ -136,6 +189,9 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
name: c_str!("rust-misc-device"),
};
+ // SAFETY: Called exactly once.
+ unsafe { DATA.init() };
+
try_pin_init!(Self {
_miscdev <- MiscDeviceRegistration::register(options),
})
@@ -185,13 +241,64 @@ fn ioctl(me: Pin<&RustMiscDevice>, _file: &File, cmd: u32, arg: usize) -> Result
RUST_MISC_DEV_SET_VALUE => me.set_value(UserSlice::new(arg, size).reader())?,
RUST_MISC_DEV_HELLO => me.hello()?,
_ => {
- dev_err!(me.dev, "-> IOCTL not recognised: {}\n", cmd);
+ dev_warn!(me.dev, "-> IOCTL not recognised: {}\n", cmd);
return Err(ENOTTY);
}
};
Ok(0)
}
+
+ fn read(
+ device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
+ mut buf: UserSliceWriter,
+ offset: &mut i64,
+ ) -> Result<i64> {
+ dev_info!(device.dev, "read() called\n");
+
+ let data = DATA.lock();
+
+ if *offset >= data.len() as i64 {
+ return Ok(0);
+ }
+
+ let slice = &data[(*offset as usize)..];
+
+ dev_info!(device.dev, "Writing to user: {:?}\n", slice);
+
+ buf.write_slice(slice)?;
+ *offset += slice.len() as i64;
+
+ Ok(data.len() as i64)
+ }
+
+ fn write(
+ device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
+ buf: UserSliceReader,
+ offset: &mut i64,
+ ) -> Result<i64> {
+ dev_info!(device.dev, "write() called\n");
+
+ let mut data = DATA.lock();
+
+ let mut tmp = KVec::with_capacity(buf.len(), GFP_KERNEL)?;
+ buf.read_all(&mut tmp, GFP_KERNEL)?;
+
+ for (i, val) in tmp.iter().enumerate() {
+ let idx = *offset as usize + i;
+ if idx < data.len() {
+ data[idx] = *val;
+ } else {
+ data.push(*val, GFP_KERNEL)?;
+ }
+ }
+
+ *offset += tmp.len() as i64;
+
+ dev_info!(device.dev, "Reading from user: {:?}\n", tmp);
+
+ Ok(*offset)
+ }
}
#[pinned_drop]
--
2.43.0
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