Merge tag 'driver-core-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core updatesk from Greg KH:
 "Here is the big set of driver core updates for 6.15-rc1. Lots of stuff
  happened this development cycle, including:

   - kernfs scaling changes to make it even faster thanks to rcu

   - bin_attribute constify work in many subsystems

   - faux bus minor tweaks for the rust bindings

   - rust binding updates for driver core, pci, and platform busses,
     making more functionaliy available to rust drivers. These are all
     due to people actually trying to use the bindings that were in
     6.14.

   - make Rafael and Danilo full co-maintainers of the driver core
     codebase

   - other minor fixes and updates"

* tag 'driver-core-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (52 commits)
  rust: platform: require Send for Driver trait implementers
  rust: pci: require Send for Driver trait implementers
  rust: platform: impl Send + Sync for platform::Device
  rust: pci: impl Send + Sync for pci::Device
  rust: platform: fix unrestricted &mut platform::Device
  rust: pci: fix unrestricted &mut pci::Device
  rust: device: implement device context marker
  rust: pci: use to_result() in enable_device_mem()
  MAINTAINERS: driver core: mark Rafael and Danilo as co-maintainers
  rust/kernel/faux: mark Registration methods inline
  driver core: faux: only create the device if probe() succeeds
  rust/faux: Add missing parent argument to Registration::new()
  rust/faux: Drop #[repr(transparent)] from faux::Registration
  rust: io: fix devres test with new io accessor functions
  rust: io: rename `io::Io` accessors
  kernfs: Move dput() outside of the RCU section.
  efi: rci2: mark bin_attribute as __ro_after_init
  rapidio: constify 'struct bin_attribute'
  firmware: qemu_fw_cfg: constify 'struct bin_attribute'
  powerpc/perf/hv-24x7: Constify 'struct bin_attribute'
  ...

1 files changed, 73 insertions, 31 deletions

diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index 1297f5292ba9..4917cb34e2fe 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs
@@ -5,7 +5,7 @@
 //! C header: [`include/linux/platform_device.h`](srctree/include/linux/platform_device.h)
 
 use crate::{
-    bindings, container_of, device, driver,
+    bindings, device, driver,
     error::{to_result, Result},
     of,
     prelude::*,
@@ -14,7 +14,11 @@ use crate::{
     ThisModule,
 };
 
-use core::ptr::addr_of_mut;
+use core::{
+    marker::PhantomData,
+    ops::Deref,
+    ptr::{addr_of_mut, NonNull},
+};
 
 /// An adapter for the registration of platform drivers.
 pub struct Adapter<T: Driver>(T);
@@ -54,14 +58,14 @@ unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
 
 impl<T: Driver + 'static> Adapter<T> {
     extern "C" fn probe_callback(pdev: *mut bindings::platform_device) -> kernel::ffi::c_int {
-        // SAFETY: The platform bus only ever calls the probe callback with a valid `pdev`.
-        let dev = unsafe { device::Device::get_device(addr_of_mut!((*pdev).dev)) };
-        // SAFETY: `dev` is guaranteed to be embedded in a valid `struct platform_device` by the
-        // call above.
-        let mut pdev = unsafe { Device::from_dev(dev) };
+        // SAFETY: The platform bus only ever calls the probe callback with a valid pointer to a
+        // `struct platform_device`.
+        //
+        // INVARIANT: `pdev` is valid for the duration of `probe_callback()`.
+        let pdev = unsafe { &*pdev.cast::<Device<device::Core>>() };
 
         let info = <Self as driver::Adapter>::id_info(pdev.as_ref());
-        match T::probe(&mut pdev, info) {
+        match T::probe(pdev, info) {
             Ok(data) => {
                 // Let the `struct platform_device` own a reference of the driver's private data.
                 // SAFETY: By the type invariant `pdev.as_raw` returns a valid pointer to a
@@ -120,7 +124,7 @@ macro_rules! module_platform_driver {
 /// # Example
 ///
 ///```
-/// # use kernel::{bindings, c_str, of, platform};
+/// # use kernel::{bindings, c_str, device::Core, of, platform};
 ///
 /// struct MyDriver;
 ///
@@ -138,14 +142,14 @@ macro_rules! module_platform_driver {
 ///     const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
 ///
 ///     fn probe(
-///         _pdev: &mut platform::Device,
+///         _pdev: &platform::Device<Core>,
 ///         _id_info: Option<&Self::IdInfo>,
 ///     ) -> Result<Pin<KBox<Self>>> {
 ///         Err(ENODEV)
 ///     }
 /// }
 ///```
-pub trait Driver {
+pub trait Driver: Send {
     /// The type holding driver private data about each device id supported by the driver.
     ///
     /// TODO: Use associated_type_defaults once stabilized:
@@ -160,41 +164,79 @@ pub trait Driver {
     ///
     /// Called when a new platform device is added or discovered.
     /// Implementers should attempt to initialize the device here.
-    fn probe(dev: &mut Device, id_info: Option<&Self::IdInfo>) -> Result<Pin<KBox<Self>>>;
+    fn probe(dev: &Device<device::Core>, id_info: Option<&Self::IdInfo>)
+        -> Result<Pin<KBox<Self>>>;
 }
 
 /// The platform device representation.
 ///
-/// A platform device is based on an always reference counted `device:Device` instance. Cloning a
-/// platform device, hence, also increments the base device' reference count.
+/// This structure represents the Rust abstraction for a C `struct platform_device`. The
+/// implementation abstracts the usage of an already existing C `struct platform_device` within Rust
+/// code that we get passed from the C side.
 ///
 /// # Invariants
 ///
-/// `Device` holds a valid reference of `ARef<device::Device>` whose underlying `struct device` is a
-/// member of a `struct platform_device`.
-#[derive(Clone)]
-pub struct Device(ARef<device::Device>);
+/// A [`Device`] instance represents a valid `struct platform_device` created by the C portion of
+/// the kernel.
+#[repr(transparent)]
+pub struct Device<Ctx: device::DeviceContext = device::Normal>(
+    Opaque<bindings::platform_device>,
+    PhantomData<Ctx>,
+);
 
 impl Device {
-    /// Convert a raw kernel device into a `Device`
-    ///
-    /// # Safety
-    ///
-    /// `dev` must be an `Aref<device::Device>` whose underlying `bindings::device` is a member of a
-    /// `bindings::platform_device`.
-    unsafe fn from_dev(dev: ARef<device::Device>) -> Self {
-        Self(dev)
+    fn as_raw(&self) -> *mut bindings::platform_device {
+        self.0.get()
     }
+}
 
-    fn as_raw(&self) -> *mut bindings::platform_device {
-        // SAFETY: By the type invariant `self.0.as_raw` is a pointer to the `struct device`
-        // embedded in `struct platform_device`.
-        unsafe { container_of!(self.0.as_raw(), bindings::platform_device, dev) }.cast_mut()
+impl Deref for Device<device::Core> {
+    type Target = Device;
+
+    fn deref(&self) -> &Self::Target {
+        let ptr: *const Self = self;
+
+        // CAST: `Device<Ctx>` is a transparent wrapper of `Opaque<bindings::platform_device>`.
+        let ptr = ptr.cast::<Device>();
+
+        // SAFETY: `ptr` was derived from `&self`.
+        unsafe { &*ptr }
+    }
+}
+
+impl From<&Device<device::Core>> for ARef<Device> {
+    fn from(dev: &Device<device::Core>) -> Self {
+        (&**dev).into()
+    }
+}
+
+// SAFETY: Instances of `Device` are always reference-counted.
+unsafe impl crate::types::AlwaysRefCounted for Device {
+    fn inc_ref(&self) {
+        // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
+        unsafe { bindings::get_device(self.as_ref().as_raw()) };
+    }
+
+    unsafe fn dec_ref(obj: NonNull<Self>) {
+        // SAFETY: The safety requirements guarantee that the refcount is non-zero.
+        unsafe { bindings::platform_device_put(obj.cast().as_ptr()) }
     }
 }
 
 impl AsRef<device::Device> for Device {
     fn as_ref(&self) -> &device::Device {
-        &self.0
+        // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
+        // `struct platform_device`.
+        let dev = unsafe { addr_of_mut!((*self.as_raw()).dev) };
+
+        // SAFETY: `dev` points to a valid `struct device`.
+        unsafe { device::Device::as_ref(dev) }
     }
 }
+
+// SAFETY: A `Device` is always reference-counted and can be released from any thread.
+unsafe impl Send for Device {}
+
+// SAFETY: `Device` can be shared among threads because all methods of `Device`
+// (i.e. `Device<Normal>) are thread safe.
+unsafe impl Sync for Device {}