rust: add device::Data

Based on
https://github.com/Rust-for-Linux/linux/commit/9d7d4827356cc4c17e1e546175204b12f1becff9

1 files changed, 122 insertions, 2 deletions

diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index b591afd3d7be..b342d623ba88 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -5,8 +5,25 @@
 //!
 //! C header: [`include/linux/device.h`](../../../../include/linux/device.h)
 
-use crate::{bindings, error::code::*, error::Error, error::Result, str::CStr};
-use core::fmt;
+use macros::pin_data;
+
+use crate::{
+    bindings,
+    error::code::*,
+    error::Error,
+    error::Result,
+    init::InPlaceInit,
+    init::PinInit,
+    pin_init,
+    revocable::{Revocable, RevocableGuard},
+    str::CStr,
+    sync::{LockClassKey, RevocableMutex, UniqueArc},
+};
+use core::{
+    fmt,
+    ops::{Deref, DerefMut},
+    pin::Pin,
+};
 
 /// A raw device.
 ///
@@ -257,3 +274,106 @@ impl Clone for Device {
         Self::from_dev(self)
     }
 }
+
+/// Device data.
+///
+/// When a device is removed (for whatever reason, for example, because the device was unplugged or
+/// because the user decided to unbind the driver), the driver is given a chance to clean its state
+/// up, and all io resources should ideally not be used anymore.
+///
+/// However, the device data is reference-counted because other subsystems hold pointers to it. So
+/// some device state must be freed and not used anymore, while others must remain accessible.
+///
+/// This struct separates the device data into three categories:
+///   1. Registrations: are destroyed when the device is removed, but before the io resources
+///      become inaccessible.
+///   2. Io resources: are available until the device is removed.
+///   3. General data: remain available as long as the ref count is nonzero.
+///
+/// This struct implements the `DeviceRemoval` trait so that it can clean resources up even if not
+/// explicitly called by the device drivers.
+#[pin_data]
+pub struct Data<T, U, V> {
+    #[pin]
+    registrations: RevocableMutex<T>,
+    #[pin]
+    resources: Revocable<U>,
+    #[pin]
+    general: V,
+}
+
+/// Safely creates an new reference-counted instance of [`Data`].
+#[doc(hidden)]
+#[macro_export]
+macro_rules! new_device_data {
+    ($reg:expr, $res:expr, $gen:expr, $name:literal) => {{
+        static CLASS1: $crate::sync::LockClassKey = $crate::sync::LockClassKey::new();
+        let regs = $reg;
+        let res = $res;
+        let gen = $gen;
+        let name = $crate::c_str!($name);
+        $crate::device::Data::try_new(regs, res, gen, name, &CLASS1)
+    }};
+}
+
+impl<T, U, V> Data<T, U, V> {
+    /// Creates a new instance of `Data`.
+    ///
+    /// It is recommended that the [`new_device_data`] macro be used as it automatically creates
+    /// the lock classes.
+    pub fn try_new(
+        registrations: T,
+        resources: impl PinInit<U>,
+        general: impl PinInit<V>,
+        name: &'static CStr,
+        key1: &'static LockClassKey,
+    ) -> Result<Pin<UniqueArc<Self>>> {
+        let mut ret = UniqueArc::pin_init(pin_init!(Self {
+            registrations <- RevocableMutex::new(
+                registrations,
+                name,
+                key1,
+            ),
+            resources <- Revocable::new(resources),
+            general <- general,
+        }))?;
+
+        Ok(ret)
+    }
+
+    /// Returns the resources if they're still available.
+    pub fn resources(&self) -> Option<RevocableGuard<'_, U>> {
+        self.resources.try_access()
+    }
+
+    /// Returns the locked registrations if they're still available.
+    #[cfg(disabled)]
+    pub fn registrations(&self) -> Option<RevocableMutexGuard<'_, T>> {
+        self.registrations.try_write()
+    }
+}
+
+impl<T, U, V> crate::driver::DeviceRemoval for Data<T, U, V> {
+    fn device_remove(&self) {
+        // We revoke the registrations first so that resources are still available to them during
+        // unregistration.
+        self.registrations.revoke();
+
+        // Release resources now. General data remains available.
+        self.resources.revoke();
+    }
+}
+
+impl<T, U, V> Deref for Data<T, U, V> {
+    type Target = V;
+
+    fn deref(&self) -> &V {
+        &self.general
+    }
+}
+
+impl<T, U, V> DerefMut for Data<T, U, V> {
+    fn deref_mut(&mut self) -> &mut V {
+        &mut self.general
+    }
+}