[RFC,V2,5/8] rust: Extend cpufreq bindings for policy and driver ops

diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs
index 51a4a9bd8d3c..d5679272e40b 100644
--- a/rust/kernel/cpufreq.rs
+++ b/rust/kernel/cpufreq.rs
@@ -7,15 +7,20 @@ 
 //! C header: [`include/linux/cpufreq.h`](../../../../../../include/linux/cpufreq.h)
 
 use crate::{
-    bindings,
-    error::{code::*, to_result, Result},
+    bindings, clk, cpumask,
+    device::Device,
+    error::{code::*, from_err_ptr, to_result, Result, VTABLE_DEFAULT_ERROR},
     prelude::*,
+    types::{ARef, ForeignOwnable},
 };
 
 use core::{
     pin::Pin,
+    ptr::self,
 };
 
+use macros::vtable;
+
 /// Default transition latency value.
 pub const ETERNAL_LATENCY: u32 = bindings::CPUFREQ_ETERNAL as u32;
 
@@ -249,3 +254,329 @@  pub fn data(&self, index: usize) -> Result<u32> {
         Ok(unsafe { (*self.ptr.add(index)).driver_data })
     }
 }
+
+/// Equivalent to `struct cpufreq_policy` in the C code.
+pub struct Policy {
+    ptr: *mut bindings::cpufreq_policy,
+    put_cpu: bool,
+    cpumask: cpumask::Cpumask,
+}
+
+impl Policy {
+    /// Creates a new instance of [`Policy`].
+    ///
+    /// # Safety
+    ///
+    /// Callers must ensure that `ptr` is valid and non-null.
+    pub unsafe fn from_ptr(ptr: *mut bindings::cpufreq_policy) -> Self {
+        Self {
+            ptr,
+            put_cpu: false,
+            // SAFETY: The pointer is guaranteed to be valid for the lifetime of `Self`. The `cpus`
+            // pointer is guaranteed to be valid by the C code.
+            cpumask: unsafe { cpumask::Cpumask::new((*ptr).cpus) },
+        }
+    }
+
+    fn from_cpu(cpu: u32) -> Result<Self> {
+        // SAFETY: It is safe to call `cpufreq_cpu_get()` for any CPU.
+        let ptr = from_err_ptr(unsafe { bindings::cpufreq_cpu_get(cpu) })?;
+
+        // SAFETY: The pointer is guaranteed to be valid by the C code.
+        let mut policy = unsafe { Policy::from_ptr(ptr) };
+        policy.put_cpu = true;
+        Ok(policy)
+    }
+
+    /// Raw pointer to the underlying cpufreq policy.
+    pub fn as_ptr(&self) -> *mut bindings::cpufreq_policy {
+        self.ptr
+    }
+
+    fn as_ref(&self) -> &bindings::cpufreq_policy {
+        // SAFETY: By the type invariants, we know that `self` owns a reference to the pointer.
+        unsafe { &(*self.ptr) }
+    }
+    fn as_mut_ref(&mut self) -> &mut bindings::cpufreq_policy {
+        // SAFETY: By the type invariants, we know that `self` owns a reference to the pointer.
+        unsafe { &mut (*self.ptr) }
+    }
+
+    /// Returns the primary CPU for a cpufreq policy.
+    pub fn cpu(&self) -> u32 {
+        self.as_ref().cpu
+    }
+
+    /// Returns the minimum frequency for a cpufreq policy.
+    pub fn min(&self) -> u32 {
+        self.as_ref().min
+    }
+
+    /// Returns the maximum frequency for a cpufreq policy.
+    pub fn max(&self) -> u32 {
+        self.as_ref().max
+    }
+
+    /// Returns the current frequency for a cpufreq policy.
+    pub fn cur(&self) -> u32 {
+        self.as_ref().cur
+    }
+
+    /// Sets the suspend frequency for a cpufreq policy.
+    pub fn set_suspend_freq(&mut self, freq: u32) -> &mut Self {
+        self.as_mut_ref().suspend_freq = freq;
+        self
+    }
+
+    /// Returns the suspend frequency for a cpufreq policy.
+    pub fn suspend_freq(&self) -> u32 {
+        self.as_ref().suspend_freq
+    }
+
+    /// Provides a wrapper to the generic suspend routine.
+    pub fn generic_suspend(&self) -> Result<()> {
+        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
+        // use it now.
+        to_result(unsafe { bindings::cpufreq_generic_suspend(self.as_ptr()) })
+    }
+
+    /// Provides a wrapper to the generic get routine.
+    pub fn generic_get(&self) -> Result<u32> {
+        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
+        // use it now.
+        Ok(unsafe { bindings::cpufreq_generic_get(self.cpu()) })
+    }
+
+    /// Provides a wrapper to the register em with OPP routine.
+    pub fn register_em_opp(&self) {
+        // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
+        // use it now.
+        unsafe { bindings::cpufreq_register_em_with_opp(self.as_ptr()) };
+    }
+
+    /// Gets raw pointer to cpufreq policy's CPUs mask.
+    pub fn cpus(&mut self) -> &mut cpumask::Cpumask {
+        &mut self.cpumask
+    }
+
+    /// Sets CPUs mask for a cpufreq policy.
+    ///
+    /// Update the `cpus` mask with a single CPU.
+    pub fn set_cpus(&mut self, cpu: u32) -> &mut Self {
+        // SAFETY: The `cpus` pointer is guaranteed to be valid for the lifetime of `self`. And it
+        // is safe to call `cpumask_set_cpus()` for any CPU.
+        unsafe { bindings::cpumask_set_cpu(cpu, self.cpus().as_mut_ptr()) };
+        self
+    }
+
+    /// Sets CPUs mask for a cpufreq policy.
+    ///
+    /// Update the `cpus` mask with a single CPU if `cpu` is set to `Some(cpu)`, else sets all
+    /// CPUs.
+    pub fn set_all_cpus(&mut self) -> &mut Self {
+        // SAFETY: The `cpus` pointer is guaranteed to be valid for the lifetime of `self`. And it
+        // is safe to call `cpumask_setall()`.
+        unsafe { bindings::cpumask_setall(self.cpus().as_mut_ptr()) };
+        self
+    }
+
+    /// Sets clock for a cpufreq policy.
+    pub fn set_clk(&mut self, dev: ARef<Device>, name: Option<&CStr>) -> Result<clk::Clk> {
+        let clk = clk::Clk::new(dev, name)?;
+        self.as_mut_ref().clk = clk.as_ptr();
+        Ok(clk)
+    }
+
+    /// Allows frequency switching code to run on any CPU.
+    pub fn set_dvfs_possible_from_any_cpu(&mut self) -> &mut Self {
+        self.as_mut_ref().dvfs_possible_from_any_cpu = true;
+        self
+    }
+
+    /// Sets transition latency for a cpufreq policy.
+    pub fn set_transition_latency(&mut self, latency: u32) -> &mut Self {
+        self.as_mut_ref().cpuinfo.transition_latency = latency;
+        self
+    }
+
+    /// Returns the cpufreq table for a cpufreq policy. The cpufreq table is recreated in a
+    /// light-weight manner from the raw pointer. The table in C code is not freed once this table
+    /// is dropped.
+    pub fn freq_table(&self) -> Result<Table> {
+        if self.as_ref().freq_table == ptr::null_mut() {
+            return Err(EINVAL);
+        }
+
+        // SAFETY: The `freq_table` is guaranteed to be valid.
+        Ok(unsafe { Table::from_raw(self.as_ref().freq_table) })
+    }
+
+    /// Sets the cpufreq table for a cpufreq policy.
+    ///
+    /// The cpufreq driver must guarantee that the frequency table does not get freed while it is
+    /// still being used by the C code.
+    pub fn set_freq_table(&mut self, table: &Table) -> &mut Self {
+        self.as_mut_ref().freq_table = table.as_ptr();
+        self
+    }
+
+    /// Returns the data for a cpufreq policy.
+    pub fn data<T: ForeignOwnable>(&mut self) -> Option<<T>::Borrowed<'_>> {
+        if self.as_ref().driver_data.is_null() {
+            None
+        } else {
+            // SAFETY: The data is earlier set by us from [`set_data()`].
+            Some(unsafe { T::borrow(self.as_ref().driver_data) })
+        }
+    }
+
+    // Sets the data for a cpufreq policy.
+    fn set_data<T: ForeignOwnable>(&mut self, data: T) -> Result<()> {
+        if self.as_ref().driver_data.is_null() {
+            // Pass the ownership of the data to the foreign interface.
+            self.as_mut_ref().driver_data = <T as ForeignOwnable>::into_foreign(data) as _;
+            Ok(())
+        } else {
+            Err(EBUSY)
+        }
+    }
+
+    // Returns the data for a cpufreq policy.
+    fn clear_data<T: ForeignOwnable>(&mut self) -> Option<T> {
+        if self.as_ref().driver_data.is_null() {
+            None
+        } else {
+            // SAFETY: The data is earlier set by us from [`set_data()`]. It is safe to take back
+            // the ownership of the data from the foreign interface.
+            let data =
+                Some(unsafe { <T as ForeignOwnable>::from_foreign(self.as_ref().driver_data) });
+            self.as_mut_ref().driver_data = ptr::null_mut();
+            data
+        }
+    }
+}
+
+impl Drop for Policy {
+    fn drop(&mut self) {
+        if self.put_cpu {
+            // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to
+            // relinquish it now.
+            unsafe { bindings::cpufreq_cpu_put(self.as_ptr()) };
+        }
+    }
+}
+
+/// Operations to be implemented by a cpufreq driver.
+#[vtable]
+pub trait DriverOps {
+    /// Driver specific data.
+    ///
+    /// Corresponds to the data retrieved via the kernel's
+    /// `cpufreq_get_driver_data()` function.
+    ///
+    /// Require that `Data` implements `ForeignOwnable`. We guarantee to
+    /// never move the underlying wrapped data structure.
+    type Data: ForeignOwnable;
+
+    /// Policy specific data.
+    ///
+    /// Require that `PData` implements `ForeignOwnable`. We guarantee to
+    /// never move the underlying wrapped data structure.
+    type PData: ForeignOwnable;
+
+    /// Policy's init callback.
+    fn init(policy: &mut Policy) -> Result<Self::PData>;
+
+    /// Policy's exit callback.
+    fn exit(_policy: &mut Policy, _data: Option<Self::PData>) -> Result<()> {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's online callback.
+    fn online(_policy: &mut Policy) -> Result<()> {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's offline callback.
+    fn offline(_policy: &mut Policy) -> Result<()> {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's suspend callback.
+    fn suspend(_policy: &mut Policy) -> Result<()> {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's resume callback.
+    fn resume(_policy: &mut Policy) -> Result<()> {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's ready callback.
+    fn ready(_policy: &mut Policy) {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's verify callback.
+    fn verify(data: &mut PolicyData) -> Result<()>;
+
+    /// Policy's setpolicy callback.
+    fn setpolicy(_policy: &mut Policy) -> Result<()> {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's target callback.
+    fn target(_policy: &mut Policy, _target_freq: u32, _relation: Relation) -> Result<()> {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's target_index callback.
+    fn target_index(_policy: &mut Policy, _index: u32) -> Result<()> {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's fast_switch callback.
+    fn fast_switch(_policy: &mut Policy, _target_freq: u32) -> u32 {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's adjust_perf callback.
+    fn adjust_perf(_policy: &mut Policy, _min_perf: u64, _target_perf: u64, _capacity: u64) {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's get_intermediate callback.
+    fn get_intermediate(_policy: &mut Policy, _index: u32) -> u32 {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's target_intermediate callback.
+    fn target_intermediate(_policy: &mut Policy, _index: u32) -> Result<()> {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's get callback.
+    fn get(_policy: &mut Policy) -> Result<u32> {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's update_limits callback.
+    fn update_limits(_policy: &mut Policy) {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's bios_limit callback.
+    fn bios_limit(_policy: &mut Policy, _limit: &mut u32) -> Result<()> {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's set_boost callback.
+    fn set_boost(_policy: &mut Policy, _state: i32) -> Result<()> {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Policy's register_em callback.
+    fn register_em(_policy: &mut Policy) {
+        kernel::build_error(VTABLE_DEFAULT_ERROR)
+    }
+}