[PATCH V8 05/14] rust: Add bindings for cpumask

[Viresh Kumar <viresh.kumar@linaro.org>]

This patch adds basic Rust bindings for struct cpumask.

These will be used by Rust based cpufreq / OPP core.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 MAINTAINERS            |   1 +
 rust/kernel/cpumask.rs | 138 +++++++++++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs     |   1 +
 3 files changed, 140 insertions(+)
 create mode 100644 rust/kernel/cpumask.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index bfc1bf2ebd77..ff4511914e0a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4022,6 +4022,7 @@ F:	lib/find_bit.c
 F:	lib/find_bit_benchmark.c
 F:	lib/test_bitmap.c
 F:	rust/helpers/cpumask.c
+F:	rust/kernel/cpumask.rs
 F:	tools/include/linux/bitfield.h
 F:	tools/include/linux/bitmap.h
 F:	tools/include/linux/bits.h
diff --git a/rust/kernel/cpumask.rs b/rust/kernel/cpumask.rs
new file mode 100644
index 000000000000..b0be8c75a2c2
--- /dev/null
+++ b/rust/kernel/cpumask.rs
@@ -0,0 +1,138 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! CPU mask abstractions.
+//!
+//! C header: [`include/linux/cpumask.h`](srctree/include/linux/cpumask.h)
+
+use crate::{bindings, error::Result, prelude::ENOMEM};
+
+#[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+use crate::prelude::{KBox, GFP_KERNEL};
+
+#[cfg(CONFIG_CPUMASK_OFFSTACK)]
+use core::ptr;
+
+/// A simple implementation of `struct cpumask` from the C code.
+pub struct Cpumask {
+    ptr: *mut bindings::cpumask,
+    owned: bool,
+}
+
+impl Cpumask {
+    /// Creates empty cpumask.
+    #[cfg(CONFIG_CPUMASK_OFFSTACK)]
+    pub fn new() -> Result<Self> {
+        let mut ptr: *mut bindings::cpumask = ptr::null_mut();
+
+        // SAFETY: Depending on the value of `gfp_flags`, this call may sleep. Other than that, it
+        // is always safe to call this method.
+        if !unsafe { bindings::zalloc_cpumask_var(&mut ptr, bindings::GFP_KERNEL) } {
+            return Err(ENOMEM);
+        }
+
+        Ok(Self { ptr, owned: true })
+    }
+
+    /// Creates empty cpumask.
+    #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+    pub fn new() -> Result<Self> {
+        let ptr = KBox::into_raw(KBox::new([bindings::cpumask::default(); 1], GFP_KERNEL)?);
+
+        // SAFETY: Depending on the value of `gfp_flags`, this call may sleep. Other than that, it
+        // is always safe to call this method.
+        if !unsafe { bindings::zalloc_cpumask_var(ptr, bindings::GFP_KERNEL) } {
+            return Err(ENOMEM);
+        }
+
+        Ok(Self {
+            ptr: ptr as *mut _,
+            owned: true,
+        })
+    }
+
+    /// Creates a new abstraction instance of an existing `struct cpumask` pointer.
+    ///
+    /// # Safety
+    ///
+    /// Callers must ensure that `ptr` is valid, and non-null.
+    #[cfg(CONFIG_CPUMASK_OFFSTACK)]
+    pub unsafe fn get_cpumask(ptr: &mut *mut bindings::cpumask) -> Self {
+        Self {
+            ptr: *ptr,
+            owned: false,
+        }
+    }
+
+    /// Creates a new abstraction instance of an existing `struct cpumask` pointer.
+    ///
+    /// # Safety
+    ///
+    /// Callers must ensure that `ptr` is valid, and non-null.
+    #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+    pub unsafe fn get_cpumask(ptr: &mut bindings::cpumask_var_t) -> Self {
+        Self {
+            ptr: ptr as *mut _,
+            owned: false,
+        }
+    }
+
+    /// Obtain the raw `struct cpumask *`.
+    pub fn as_raw(&mut self) -> *mut bindings::cpumask {
+        self.ptr
+    }
+
+    /// Sets CPU in the cpumask.
+    ///
+    /// Update the cpumask with a single CPU.
+    pub fn set(&mut self, cpu: u32) {
+        // SAFETY: `ptr` 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.ptr) };
+    }
+
+    /// Clears CPU in the cpumask.
+    ///
+    /// Update the cpumask with a single CPU.
+    pub fn clear(&mut self, cpu: i32) {
+        // SAFETY: `ptr` is guaranteed to be valid for the lifetime of `self`. And it is safe to
+        // call `cpumask_clear_cpu()` for any CPU.
+        unsafe { bindings::cpumask_clear_cpu(cpu, self.ptr) };
+    }
+
+    /// Sets all CPUs in the cpumask.
+    pub fn set_all(&mut self) {
+        // SAFETY: `ptr` is guaranteed to be valid for the lifetime of `self`. And it is safe to
+        // call `cpumask_setall()`.
+        unsafe { bindings::cpumask_setall(self.ptr) };
+    }
+
+    /// Gets weight of a cpumask.
+    pub fn weight(&self) -> u32 {
+        // SAFETY: `ptr` is guaranteed to be valid for the lifetime of `self`. And it is safe to
+        // call `cpumask_weight()`.
+        unsafe { bindings::cpumask_weight(self.ptr) }
+    }
+
+    /// Copies cpumask.
+    pub fn copy(&self, dstp: &mut Self) {
+        // SAFETY: `ptr` is guaranteed to be valid for the lifetime of `self`. And it is safe to
+        // call `cpumask_copy()`.
+        unsafe { bindings::cpumask_copy(dstp.as_raw(), self.ptr) };
+    }
+}
+
+impl Drop for Cpumask {
+    fn drop(&mut self) {
+        if self.owned {
+            // SAFETY: `ptr` is guaranteed to be valid for the lifetime of `self`. And it is safe
+            // to call `free_cpumask_var()`.
+            unsafe { bindings::free_cpumask_var(self.ptr) }
+
+            #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+            // SAFETY: The pointer was earlier initialized from the result of `KBox::into_raw()`.
+            unsafe {
+                drop(KBox::from_raw(self.ptr))
+            };
+        }
+    }
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 415c500212dd..ccbf7fa087a0 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -41,6 +41,7 @@
 #[doc(hidden)]
 pub mod build_assert;
 pub mod cpu;
+pub mod cpumask;
 pub mod cred;
 pub mod device;
 pub mod device_id;
-- 
2.31.1.272.g89b43f80a514