Initial commit

src/lib.rs

@@ -0,0 +1,87 @@
+mod low_level_zbus_api;
+
+#[derive(thiserror::Error, Debug)]
+pub enum Error {
+    #[error("Permission denied")]
+    PermissionDenied,
+
+    #[error(transparent)]
+    ZbusError(#[from] zbus::Error),
+
+    #[error(transparent)]
+    ZbusMethodError(#[from] zbus::fdo::Error),
+}
+
+/// Helper for [make_thread_realtime], uses the current thread's tid.
+pub fn make_current_thread_realtime(priority: Option<u32>) -> Result<u32, Error> {
+    let thread_id = nix::unistd::gettid().as_raw().try_into().unwrap();
+    make_thread_realtime(thread_id, priority)
+}
+
+/// Elevates the realtime priority of a thread as close as possible to the requested priority.
+///
+/// If no priority is specified, the maximum priority allowed by the system will be used.
+///
+/// Returns the actual priority that was set.
+pub fn make_thread_realtime(tid: u64, priority: Option<u32>) -> Result<u32, Error> {
+    debug_assert!(
+        priority.is_some_and(|p| p <= 99),
+        "priority must be between 0 and 99"
+    );
+
+    let connection = zbus::blocking::Connection::system()?;
+    let proxy = low_level_zbus_api::RTKitProxyBlocking::builder(&connection)
+        .cache_properties(zbus::proxy::CacheProperties::No)
+        .build()?;
+
+    let max_realtime_priority = proxy.max_realtime_priority()?;
+    debug_assert!(
+        (0..=99).contains(&max_realtime_priority),
+        "max_realtime_priority must be between 0 and 99"
+    );
+    let priority = priority.unwrap_or(max_realtime_priority as u32);
+
+    proxy
+        .make_thread_realtime(tid, priority)
+        .map(|_| priority)
+        .map_err(|e| match e {
+            zbus::fdo::Error::AccessDenied(_) => Error::PermissionDenied,
+            e => Error::ZbusMethodError(e),
+        })
+}
+
+/// Elevates the realtime priority of a specified processes thread as close as possible to the requested priority.
+///
+/// If no priority is specified, the maximum priority allowed by the system will be used.
+///
+/// Returns the actual priority that was set.
+pub fn make_process_thread_realtime(
+    pid: u64,
+    tid: u64,
+    priority: Option<u32>,
+) -> Result<u32, Error> {
+    debug_assert!(
+        priority.is_some_and(|p| p <= 99),
+        "priority must be between 0 and 99"
+    );
+
+    let connection = zbus::blocking::Connection::system()?;
+    let proxy = low_level_zbus_api::RTKitProxyBlocking::builder(&connection)
+        .cache_properties(zbus::proxy::CacheProperties::No)
+        .build()?;
+
+    let max_realtime_priority = proxy.max_realtime_priority()?;
+    debug_assert!(
+        (0..=99).contains(&max_realtime_priority),
+        "max_realtime_priority must be between 0 and 99"
+    );
+    let priority = priority.unwrap_or(max_realtime_priority as u32);
+
+    proxy
+        .make_thread_realtime_with_pid(pid, tid, priority)
+        .map(|_| priority)
+        .map_err(|e| match e {
+            zbus::fdo::Error::AccessDenied(_) => Error::PermissionDenied,
+            e => Error::ZbusMethodError(e),
+        })
+}

src/low_level_zbus_api.rs

@@ -0,0 +1,36 @@
+use zbus::{fdo::Result, proxy};
+
+/// Low level interface to the RealtimeKit1 D-Bus service.
+///
+/// Note: due to a missing implementation of GetAll in the canonical rtkit service,
+/// you will need to disable the cache for properties in order not to trigger an UnknownMethod error.
+#[proxy(
+    interface = "org.freedesktop.RealtimeKit1",
+    default_service = "org.freedesktop.RealtimeKit1",
+    default_path = "/org/freedesktop/RealtimeKit1"
+)]
+pub trait RTKit {
+    fn make_thread_realtime(&self, thread: u64, priority: u32) -> Result<()>;
+    fn make_thread_realtime_with_pid(&self, process: u64, thread: u64, priority: u32)
+        -> Result<()>;
+    fn make_thread_high_priority(&self, thread: u64, priority: i32) -> Result<()>;
+    fn make_thread_high_priority_with_pid(
+        &self,
+        process: u64,
+        thread: u64,
+        // lmao, why are these different?
+        priority: i32,
+    ) -> Result<()>;
+    fn reset_known(&self) -> Result<()>;
+    fn reset_all(&self) -> Result<()>;
+    fn exit(&self) -> Result<()>;
+
+    #[zbus(property)]
+    fn rt_time_usec_max(&self) -> Result<i64>;
+
+    #[zbus(property)]
+    fn max_realtime_priority(&self) -> Result<i32>;
+
+    #[zbus(property)]
+    fn min_nice_level(&self) -> Result<i32>;
+}