[PATCH V8 12/14] rust: Extend cpufreq bindings for driver registration

Viresh Kumar
2025-02-06T09:29:40Z

This extends the cpufreq bindings with bindings for registering a
driver.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
rust/kernel/cpufreq.rs | 475 ++++++++++++++++++++++++++++++++++++++++-
1 file changed, 473 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs
index 63ea816017c0..f92259d339d3 100644
--- a/rust/kernel/cpufreq.rs
+++ b/rust/kernel/cpufreq.rs
@@ -9,14 +9,17 @@
use crate::{
bindings, clk, cpumask,
device::Device,
- error::{code::*, from_err_ptr, to_result, Result, VTABLE_DEFAULT_ERROR},
+ devres::Devres,
+ error::{code::*, from_err_ptr, from_result, to_result, Result, VTABLE_DEFAULT_ERROR},
prelude::*,
types::ForeignOwnable,
};

use core::{
+ cell::UnsafeCell,
+ marker::PhantomData,
pin::Pin,
- ptr::self,
+ ptr::{self, addr_of_mut},
};

use macros::vtable;
@@ -579,3 +582,471 @@ fn register_em(_policy: &mut Policy) {
build_error!(VTABLE_DEFAULT_ERROR)
}
}
+
+/// Registration of a cpufreq driver.
+pub struct Registration<T: Driver> {
+ drv: KBox<UnsafeCell<bindings::cpufreq_driver>>,
+ _p: PhantomData<T>,
+}
+
+// SAFETY: `Registration` doesn't offer any methods or access to fields when shared between threads
+// or CPUs, so it is safe to share it.
+unsafe impl<T: Driver> Sync for Registration<T> {}
+
+#[allow(clippy::non_send_fields_in_send_ty)]
+// SAFETY: Registration with and unregistration from the cpufreq subsystem can happen from any
+// thread. Additionally, `T::Data` (which is dropped during unregistration) is `Send`, so it is
+// okay to move `Registration` to different threads.
+unsafe impl<T: Driver> Send for Registration<T> {}
+
+impl<T: Driver> Registration<T> {
+ /// Registers a cpufreq driver with the rest of the kernel.
+ pub fn new(name: &'static CStr, data: T::Data, flags: u16, boost: bool) -> Result<Self> {
+ let mut drv = KBox::new(
+ UnsafeCell::new(bindings::cpufreq_driver::default()),
+ GFP_KERNEL,
+ )?;
+ let drv_ref = drv.get_mut();
+
+ // Account for the trailing null character.
+ let len = name.len() + 1;
+ if len > drv_ref.name.len() {
+ return Err(EINVAL);
+ };
+
+ // SAFETY: `name` is a valid Cstr, and we are copying it to an array of equal or larger
+ // size.
+ let name = unsafe { &*(name.as_bytes_with_nul() as *const [u8]) };
+ drv_ref.name[..len].copy_from_slice(name);
+
+ drv_ref.boost_enabled = boost;
+ drv_ref.flags = flags;
+
+ // Allocate an array of 3 pointers to be passed to the C code.
+ let mut attr = KBox::new([ptr::null_mut(); 3], GFP_KERNEL)?;
+ let mut next = 0;
+
+ // SAFETY: The C code returns a valid pointer here, which is again passed to the C code in
+ // an array.
+ attr[next] =
+ unsafe { addr_of_mut!(bindings::cpufreq_freq_attr_scaling_available_freqs) as *mut _ };
+ next += 1;
+
+ if boost {
+ // SAFETY: The C code returns a valid pointer here, which is again passed to the C code
+ // in an array.
+ attr[next] =
+ unsafe { addr_of_mut!(bindings::cpufreq_freq_attr_scaling_boost_freqs) as *mut _ };
+ next += 1;
+ }
+ attr[next] = ptr::null_mut();
+
+ // Pass the ownership of the memory block to the C code. This will be freed when
+ // the [`Registration`] object goes out of scope.
+ drv_ref.attr = KBox::leak(attr) as *mut _;
+
+ // Initialize mandatory callbacks.
+ drv_ref.init = Some(Self::init_callback);
+ drv_ref.verify = Some(Self::verify_callback);
+
+ // Initialize optional callbacks.
+ drv_ref.setpolicy = if T::HAS_SETPOLICY {
+ Some(Self::setpolicy_callback)
+ } else {
+ None
+ };
+ drv_ref.target = if T::HAS_TARGET {
+ Some(Self::target_callback)
+ } else {
+ None
+ };
+ drv_ref.target_index = if T::HAS_TARGET_INDEX {
+ Some(Self::target_index_callback)
+ } else {
+ None
+ };
+ drv_ref.fast_switch = if T::HAS_FAST_SWITCH {
+ Some(Self::fast_switch_callback)
+ } else {
+ None
+ };
+ drv_ref.adjust_perf = if T::HAS_ADJUST_PERF {
+ Some(Self::adjust_perf_callback)
+ } else {
+ None
+ };
+ drv_ref.get_intermediate = if T::HAS_GET_INTERMEDIATE {
+ Some(Self::get_intermediate_callback)
+ } else {
+ None
+ };
+ drv_ref.target_intermediate = if T::HAS_TARGET_INTERMEDIATE {
+ Some(Self::target_intermediate_callback)
+ } else {
+ None
+ };
+ drv_ref.get = if T::HAS_GET {
+ Some(Self::get_callback)
+ } else {
+ None
+ };
+ drv_ref.update_limits = if T::HAS_UPDATE_LIMITS {
+ Some(Self::update_limits_callback)
+ } else {
+ None
+ };
+ drv_ref.bios_limit = if T::HAS_BIOS_LIMIT {
+ Some(Self::bios_limit_callback)
+ } else {
+ None
+ };
+ drv_ref.online = if T::HAS_ONLINE {
+ Some(Self::online_callback)
+ } else {
+ None
+ };
+ drv_ref.offline = if T::HAS_OFFLINE {
+ Some(Self::offline_callback)
+ } else {
+ None
+ };
+ drv_ref.exit = if T::HAS_EXIT {
+ Some(Self::exit_callback)
+ } else {
+ None
+ };
+ drv_ref.suspend = if T::HAS_SUSPEND {
+ Some(Self::suspend_callback)
+ } else {
+ None
+ };
+ drv_ref.resume = if T::HAS_RESUME {
+ Some(Self::resume_callback)
+ } else {
+ None
+ };
+ drv_ref.ready = if T::HAS_READY {
+ Some(Self::ready_callback)
+ } else {
+ None
+ };
+ drv_ref.set_boost = if T::HAS_SET_BOOST {
+ Some(Self::set_boost_callback)
+ } else {
+ None
+ };
+ drv_ref.register_em = if T::HAS_REGISTER_EM {
+ Some(Self::register_em_callback)
+ } else {
+ None
+ };
+
+ // Set driver data before registering the driver, as the cpufreq core may call few
+ // callbacks before `cpufreq_register_driver()` returns.
+ Self::set_data(drv_ref, data)?;
+
+ // SAFETY: It is safe to register the driver with the cpufreq core in the C code.
+ to_result(unsafe { bindings::cpufreq_register_driver(drv_ref) })?;
+
+ Ok(Self {
+ drv,
+ _p: PhantomData,
+ })
+ }
+
+ /// Same as [Registration::new`], but does not return a `Registration` instance.
+ /// Instead the `Registration` is owned by devres and will be revoked / dropped, once the
+ /// device is detached.
+ pub fn new_foreign_owned(
+ dev: &Device,
+ name: &'static CStr,
+ data: T::Data,
+ flags: u16,
+ boost: bool,
+ ) -> Result<()> {
+ let reg = Self::new(name, data, flags, boost)?;
+ Devres::new_foreign_owned(dev, reg, GFP_KERNEL)?;
+ Ok(())
+ }
+
+ // Sets the data for a cpufreq driver.
+ fn set_data(drv: &mut bindings::cpufreq_driver, data: T::Data) -> Result<()> {
+ if drv.driver_data.is_null() {
+ // Pass the ownership of the data to the foreign interface.
+ drv.driver_data = <T::Data as ForeignOwnable>::into_foreign(data) as _;
+ Ok(())
+ } else {
+ Err(EBUSY)
+ }
+ }
+
+ /// Returns the previous set data for a cpufreq driver.
+ pub fn data(&mut self) -> Option<<T::Data as ForeignOwnable>::Borrowed<'static>> {
+ let drv = self.drv.get_mut();
+
+ if drv.driver_data.is_null() {
+ None
+ } else {
+ // SAFETY: The data is earlier set by us from [`set_data()`].
+ Some(unsafe { <T::Data as ForeignOwnable>::borrow(drv.driver_data) })
+ }
+ }
+
+ // Clears and returns the data for a cpufreq driver.
+ fn clear_data(&mut self) -> Option<T::Data> {
+ let drv = self.drv.get_mut();
+
+ if drv.driver_data.is_null() {
+ None
+ } else {
+ // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe
+ // to relinquish it now.
+ let data = Some(unsafe { <T::Data as ForeignOwnable>::from_foreign(drv.driver_data) });
+ drv.driver_data = ptr::null_mut();
+ data
+ }
+ }
+}
+
+// cpufreq driver callbacks.
+impl<T: Driver> Registration<T> {
+ // Policy's init callback.
+ extern "C" fn init_callback(ptr: *mut bindings::cpufreq_policy) -> core::ffi::c_int {
+ from_result(|| {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for
+ // the duration of this call, so it is guaranteed to remain alive for the lifetime of
+ // `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+
+ let data = T::init(&mut policy)?;
+ policy.set_data(data)?;
+ Ok(0)
+ })
+ }
+
+ // Policy's exit callback.
+ extern "C" fn exit_callback(ptr: *mut bindings::cpufreq_policy) {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the
+ // duration of this call, so it is guaranteed to remain alive for the lifetime of
+ // `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+
+ let data = policy.clear_data();
+ let _ = T::exit(&mut policy, data);
+ }
+
+ // Policy's online callback.
+ extern "C" fn online_callback(ptr: *mut bindings::cpufreq_policy) -> core::ffi::c_int {
+ from_result(|| {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for
+ // the duration of this call, so it is guaranteed to remain alive for the lifetime of
+ // `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+ T::online(&mut policy).map(|()| 0)
+ })
+ }
+
+ // Policy's offline callback.
+ extern "C" fn offline_callback(ptr: *mut bindings::cpufreq_policy) -> core::ffi::c_int {
+ from_result(|| {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for
+ // the duration of this call, so it is guaranteed to remain alive for the lifetime of
+ // `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+ T::offline(&mut policy).map(|()| 0)
+ })
+ }
+
+ // Policy's suspend callback.
+ extern "C" fn suspend_callback(ptr: *mut bindings::cpufreq_policy) -> core::ffi::c_int {
+ from_result(|| {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for
+ // the duration of this call, so it is guaranteed to remain alive for the lifetime of
+ // `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+ T::suspend(&mut policy).map(|()| 0)
+ })
+ }
+
+ // Policy's resume callback.
+ extern "C" fn resume_callback(ptr: *mut bindings::cpufreq_policy) -> core::ffi::c_int {
+ from_result(|| {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for
+ // the duration of this call, so it is guaranteed to remain alive for the lifetime of
+ // `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+ T::resume(&mut policy).map(|()| 0)
+ })
+ }
+
+ // Policy's ready callback.
+ extern "C" fn ready_callback(ptr: *mut bindings::cpufreq_policy) {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the
+ // duration of this call, so it is guaranteed to remain alive for the lifetime of `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+ T::ready(&mut policy);
+ }
+
+ // Policy's verify callback.
+ extern "C" fn verify_callback(ptr: *mut bindings::cpufreq_policy_data) -> core::ffi::c_int {
+ from_result(|| {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for
+ // the duration of this call, so it is guaranteed to remain alive for the lifetime of
+ // `ptr`.
+ let mut data = unsafe { PolicyData::from_raw_policy_data(ptr) };
+ T::verify(&mut data).map(|()| 0)
+ })
+ }
+
+ // Policy's setpolicy callback.
+ extern "C" fn setpolicy_callback(ptr: *mut bindings::cpufreq_policy) -> core::ffi::c_int {
+ from_result(|| {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for
+ // the duration of this call, so it is guaranteed to remain alive for the lifetime of
+ // `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+ T::setpolicy(&mut policy).map(|()| 0)
+ })
+ }
+
+ // Policy's target callback.
+ extern "C" fn target_callback(
+ ptr: *mut bindings::cpufreq_policy,
+ target_freq: u32,
+ relation: u32,
+ ) -> core::ffi::c_int {
+ from_result(|| {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for
+ // the duration of this call, so it is guaranteed to remain alive for the lifetime of
+ // `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+ T::target(&mut policy, target_freq, Relation::new(relation)?).map(|()| 0)
+ })
+ }
+
+ // Policy's target_index callback.
+ extern "C" fn target_index_callback(
+ ptr: *mut bindings::cpufreq_policy,
+ index: u32,
+ ) -> core::ffi::c_int {
+ from_result(|| {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for
+ // the duration of this call, so it is guaranteed to remain alive for the lifetime of
+ // `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+ T::target_index(&mut policy, index).map(|()| 0)
+ })
+ }
+
+ // Policy's fast_switch callback.
+ extern "C" fn fast_switch_callback(
+ ptr: *mut bindings::cpufreq_policy,
+ target_freq: u32,
+ ) -> core::ffi::c_uint {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the
+ // duration of this call, so it is guaranteed to remain alive for the lifetime of `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+ T::fast_switch(&mut policy, target_freq)
+ }
+
+ // Policy's adjust_perf callback.
+ extern "C" fn adjust_perf_callback(
+ cpu: u32,
+ min_perf: usize,
+ target_perf: usize,
+ capacity: usize,
+ ) {
+ if let Ok(mut policy) = Policy::from_cpu(cpu) {
+ T::adjust_perf(&mut policy, min_perf, target_perf, capacity);
+ }
+ }
+
+ // Policy's get_intermediate callback.
+ extern "C" fn get_intermediate_callback(
+ ptr: *mut bindings::cpufreq_policy,
+ index: u32,
+ ) -> core::ffi::c_uint {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the
+ // duration of this call, so it is guaranteed to remain alive for the lifetime of `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+ T::get_intermediate(&mut policy, index)
+ }
+
+ // Policy's target_intermediate callback.
+ extern "C" fn target_intermediate_callback(
+ ptr: *mut bindings::cpufreq_policy,
+ index: u32,
+ ) -> core::ffi::c_int {
+ from_result(|| {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for
+ // the duration of this call, so it is guaranteed to remain alive for the lifetime of
+ // `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+ T::target_intermediate(&mut policy, index).map(|()| 0)
+ })
+ }
+
+ // Policy's get callback.
+ extern "C" fn get_callback(cpu: u32) -> core::ffi::c_uint {
+ Policy::from_cpu(cpu).map_or(0, |mut policy| T::get(&mut policy).map_or(0, |f| f))
+ }
+
+ // Policy's update_limit callback.
+ extern "C" fn update_limits_callback(cpu: u32) {
+ if let Ok(mut policy) = Policy::from_cpu(cpu) {
+ T::update_limits(&mut policy);
+ }
+ }
+
+ // Policy's bios_limit callback.
+ extern "C" fn bios_limit_callback(cpu: i32, limit: *mut u32) -> core::ffi::c_int {
+ from_result(|| {
+ let mut policy = Policy::from_cpu(cpu as u32)?;
+
+ // SAFETY: The pointer is guaranteed by the C code to be valid.
+ T::bios_limit(&mut policy, &mut (unsafe { *limit })).map(|()| 0)
+ })
+ }
+
+ // Policy's set_boost callback.
+ extern "C" fn set_boost_callback(
+ ptr: *mut bindings::cpufreq_policy,
+ state: i32,
+ ) -> core::ffi::c_int {
+ from_result(|| {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for
+ // the duration of this call, so it is guaranteed to remain alive for the lifetime of
+ // `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+ T::set_boost(&mut policy, state).map(|()| 0)
+ })
+ }
+
+ // Policy's register_em callback.
+ extern "C" fn register_em_callback(ptr: *mut bindings::cpufreq_policy) {
+ // SAFETY: `ptr` is valid by the contract with the C code. `policy` is alive only for the
+ // duration of this call, so it is guaranteed to remain alive for the lifetime of `ptr`.
+ let mut policy = unsafe { Policy::from_raw_policy(ptr) };
+ T::register_em(&mut policy);
+ }
+}
+
+impl<T: Driver> Drop for Registration<T> {
+ // Removes the registration from the kernel if it has completed successfully before.
+ fn drop(&mut self) {
+ pr_info!("Registration dropped\n");
+ let drv = self.drv.get_mut();
+
+ // SAFETY: The driver was earlier registered from `new()`.
+ unsafe { bindings::cpufreq_unregister_driver(drv) };
+
+ // Free the previously leaked memory to the C code.
+ if !drv.attr.is_null() {
+ // SAFETY: The pointer was earlier initialized from the result of `KBox::leak`.
+ unsafe { drop(KBox::from_raw(drv.attr)) };
+ }
+
+ // Free data
+ drop(self.clear_data());
+ }
+}
--
2.31.1.272.g89b43f80a514