Extend the OPP abstractions to include support for interacting with the
cpufreq core, including the ability to retrieve frequency tables from
OPP table.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 rust/kernel/opp.rs | 67 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/rust/kernel/opp.rs b/rust/kernel/opp.rs
index 7bf612fa0cc5..a46ac28d4464 100644
--- a/rust/kernel/opp.rs
+++ b/rust/kernel/opp.rs
@@ -20,6 +20,12 @@
     types::{ARef, AlwaysRefCounted, Opaque},
 };
 
+#[cfg(CONFIG_CPU_FREQ)]
+use crate::cpufreq;
+
+#[cfg(CONFIG_CPU_FREQ)]
+use core::ops::Deref;
+
 use core::{marker::PhantomData, ptr};
 
 use macros::vtable;
@@ -497,6 +503,60 @@ extern "C" fn config_regulators(
     }
 }
 
+/// OPP frequency table.
+///
+/// A [`cpufreq::Table`] created from [`Table`].
+#[cfg(CONFIG_CPU_FREQ)]
+pub struct FreqTable {
+    dev: ARef<Device>,
+    ptr: *mut bindings::cpufreq_frequency_table,
+}
+
+#[cfg(CONFIG_CPU_FREQ)]
+impl FreqTable {
+    /// Creates a new instance of [`FreqTable`] from [`Table`].
+    fn new(table: &Table) -> Result<Self> {
+        let mut ptr: *mut bindings::cpufreq_frequency_table = ptr::null_mut();
+
+        // SAFETY: The requirements are satisfied by the existence of [`Device`] and its safety
+        // requirements.
+        to_result(unsafe {
+            bindings::dev_pm_opp_init_cpufreq_table(table.dev.as_raw(), &mut ptr)
+        })?;
+
+        Ok(Self {
+            dev: table.dev.clone(),
+            ptr,
+        })
+    }
+
+    // Returns a reference to the underlying [`cpufreq::Table`].
+    #[inline]
+    fn table(&self) -> &cpufreq::Table {
+        // SAFETY: The `ptr` is guaranteed by the C code to be valid.
+        unsafe { cpufreq::Table::from_raw(self.ptr) }
+    }
+}
+
+#[cfg(CONFIG_CPU_FREQ)]
+impl Deref for FreqTable {
+    type Target = cpufreq::Table;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        self.table()
+    }
+}
+
+#[cfg(CONFIG_CPU_FREQ)]
+impl Drop for FreqTable {
+    fn drop(&mut self) {
+        // SAFETY: The pointer was created via `dev_pm_opp_init_cpufreq_table`, and is only freed
+        // here.
+        unsafe { bindings::dev_pm_opp_free_cpufreq_table(self.dev.as_raw(), &mut self.as_raw()) };
+    }
+}
+
 /// A reference-counted OPP table.
 ///
 /// Rust abstraction for the C `struct opp_table`.
@@ -752,6 +812,13 @@ pub fn adjust_voltage(
         })
     }
 
+    /// Creates [`FreqTable`] from [`Table`].
+    #[cfg(CONFIG_CPU_FREQ)]
+    #[inline]
+    pub fn cpufreq_table(&mut self) -> Result<FreqTable> {
+        FreqTable::new(self)
+    }
+
     /// Configures device with [`OPP`] matching the frequency value.
     #[inline]
     pub fn set_rate(&self, freq: Hertz) -> Result<()> {
-- 
2.31.1.272.g89b43f80a514