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Message-Id: <20250607-b4-rust_miscdevice_registrationdata-v5-3-b77b5b7aab5b@gmail.com>
Date: Sat, 07 Jun 2025 14:07:32 +0200
From: Christian Schrefl <chrisi.schrefl@...il.com>
To: Miguel Ojeda <ojeda@...nel.org>, Danilo Krummrich <dakr@...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>, Arnd Bergmann <arnd@...db.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Lee Jones <lee@...nel.org>,
Daniel Almeida <daniel.almeida@...labora.com>,
Benno Lossin <lossin@...nel.org>, Benno Lossin <lossin@...nel.org>
Cc: Gerald Wisböck <gerald.wisboeck@...ther.ink>,
rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
Christian Schrefl <chrisi.schrefl@...il.com>
Subject: [PATCH v5 3/3] rust: miscdevice: adjust the `rust_misc_device`
sample to use `Data`.
Add a second mutex to the `RustMiscDevice``, which is shared between all
instances of the device using an `Arc` and the `Data` of
`MiscDeviceRegistration`.
This is mostly to demonstrate the capability to share data in this way.
Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
Signed-off-by: Christian Schrefl <chrisi.schrefl@...il.com>
---
samples/rust/rust_misc_device.rs | 116 ++++++++++++++++++++++++++++++++++++---
1 file changed, 109 insertions(+), 7 deletions(-)
diff --git a/samples/rust/rust_misc_device.rs b/samples/rust/rust_misc_device.rs
index c0b912920d6c4b60e747d9d298900ad64df67339..7519ff6a79985e8bdbb7f4c79d8a6ebf160ef8cc 100644
--- a/samples/rust/rust_misc_device.rs
+++ b/samples/rust/rust_misc_device.rs
@@ -18,6 +18,8 @@
//! #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)
+//! #define RUST_MISC_DEV_GET_SHARED_VALUE _IOR('|', 0x83, int)
+//! #define RUST_MISC_DEV_SET_SHARED_VALUE _IOW('|', 0x84, int)
//!
//! int main() {
//! int value, new_value;
@@ -86,6 +88,62 @@
//! return -1;
//! }
//!
+//! value++;
+//!
+//! // Set shared value to something different
+//! printf("Submitting new shared value (%d)\n", value);
+//! ret = ioctl(fd, RUST_MISC_DEV_SET_SHARED_VALUE, &value);
+//! if (ret < 0) {
+//! perror("ioctl: Failed to submit new value");
+//! close(fd);
+//! return errno;
+//! }
+//!
+//! // Close the device file
+//! printf("Closing /dev/rust-misc-device\n");
+//! close(fd);
+//!
+//! // Open the device file again
+//! printf("Opening /dev/rust-misc-device again for reading\n");
+//! fd = open("/dev/rust-misc-device", O_RDWR);
+//! if (fd < 0) {
+//! perror("open");
+//! return errno;
+//! }
+//!
+//! // Ensure new value was applied
+//! printf("Fetching new value\n");
+//! ret = ioctl(fd, RUST_MISC_DEV_GET_SHARED_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;
+//! }
+//!
+//! value = 0;
+//! // Ensure non-shared value is still 0
+//! 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;
+//! }
+//!
//! // Close the device file
//! printf("Closing /dev/rust-misc-device\n");
//! close(fd);
@@ -105,7 +163,7 @@
miscdevice::{MiscDevice, MiscDeviceOptions, MiscDeviceRegistration},
new_mutex,
prelude::*,
- sync::Mutex,
+ sync::{Arc, Mutex},
types::ARef,
uaccess::{UserSlice, UserSliceReader, UserSliceWriter},
};
@@ -113,6 +171,8 @@
const RUST_MISC_DEV_HELLO: u32 = _IO('|' as u32, 0x80);
const RUST_MISC_DEV_GET_VALUE: u32 = _IOR::<i32>('|' as u32, 0x81);
const RUST_MISC_DEV_SET_VALUE: u32 = _IOW::<i32>('|' as u32, 0x82);
+const RUST_MISC_DEV_GET_SHARED_VALUE: u32 = _IOR::<i32>('|' as u32, 0x83);
+const RUST_MISC_DEV_SET_SHARED_VALUE: u32 = _IOW::<i32>('|' as u32, 0x84);
module! {
type: RustMiscDeviceModule,
@@ -137,7 +197,10 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
};
try_pin_init!(Self {
- _miscdev <- MiscDeviceRegistration::register(options, ()),
+ _miscdev <- MiscDeviceRegistration::register(
+ options,
+ Arc::pin_init(new_mutex!(Inner { value: 0_i32 }), GFP_KERNEL)?
+ ),
})
}
}
@@ -148,8 +211,9 @@ struct Inner {
#[pin_data(PinnedDrop)]
struct RustMiscDevice {
+ shared: Arc<Mutex<Inner>>,
#[pin]
- inner: Mutex<Inner>,
+ unique: Mutex<Inner>,
dev: ARef<Device>,
}
@@ -157,7 +221,7 @@ struct RustMiscDevice {
impl MiscDevice for RustMiscDevice {
type Ptr = Pin<KBox<Self>>;
- type Data = ();
+ type Data = Arc<Mutex<Inner>>;
fn open(_file: &File, misc: &MiscDeviceRegistration<Self>) -> Result<Pin<KBox<Self>>> {
let dev = ARef::from(misc.device());
@@ -167,7 +231,8 @@ fn open(_file: &File, misc: &MiscDeviceRegistration<Self>) -> Result<Pin<KBox<Se
KBox::try_pin_init(
try_pin_init! {
RustMiscDevice {
- inner <- new_mutex!( Inner{ value: 0_i32 } ),
+ shared: misc.data().clone(),
+ unique <- new_mutex!(Inner { value: 0_i32 }),
dev: dev,
}
},
@@ -183,6 +248,12 @@ fn ioctl(me: Pin<&RustMiscDevice>, _file: &File, cmd: u32, arg: usize) -> Result
match cmd {
RUST_MISC_DEV_GET_VALUE => me.get_value(UserSlice::new(arg, size).writer())?,
RUST_MISC_DEV_SET_VALUE => me.set_value(UserSlice::new(arg, size).reader())?,
+ RUST_MISC_DEV_GET_SHARED_VALUE => {
+ me.get_shared_value(UserSlice::new(arg, size).writer())?
+ }
+ RUST_MISC_DEV_SET_SHARED_VALUE => {
+ me.set_shared_value(UserSlice::new(arg, size).reader())?
+ }
RUST_MISC_DEV_HELLO => me.hello()?,
_ => {
dev_err!(me.dev, "-> IOCTL not recognised: {}\n", cmd);
@@ -204,7 +275,7 @@ fn drop(self: Pin<&mut Self>) {
impl RustMiscDevice {
fn set_value(&self, mut reader: UserSliceReader) -> Result<isize> {
let new_value = reader.read::<i32>()?;
- let mut guard = self.inner.lock();
+ let mut guard = self.unique.lock();
dev_info!(
self.dev,
@@ -217,7 +288,38 @@ fn set_value(&self, mut reader: UserSliceReader) -> Result<isize> {
}
fn get_value(&self, mut writer: UserSliceWriter) -> Result<isize> {
- let guard = self.inner.lock();
+ let guard = self.unique.lock();
+ let value = guard.value;
+
+ // Free-up the lock and use our locally cached instance from here
+ drop(guard);
+
+ dev_info!(
+ self.dev,
+ "-> Copying data to userspace (value: {})\n",
+ &value
+ );
+
+ writer.write::<i32>(&value)?;
+ Ok(0)
+ }
+
+ fn set_shared_value(&self, mut reader: UserSliceReader) -> Result<isize> {
+ let new_value = reader.read::<i32>()?;
+ let mut guard = self.shared.lock();
+
+ dev_info!(
+ self.dev,
+ "-> Copying data from userspace (value: {})\n",
+ new_value
+ );
+
+ guard.value = new_value;
+ Ok(0)
+ }
+
+ fn get_shared_value(&self, mut writer: UserSliceWriter) -> Result<isize> {
+ let guard = self.shared.lock();
let value = guard.value;
// Free-up the lock and use our locally cached instance from here
--
2.49.0
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