diff mbox series

[V9,09/17] rust: cpu: Add from_cpu()

Message ID 475bc73d8d11290446a4135af76aea123c6d80ee.1744366571.git.viresh.kumar@linaro.org
State New
Headers show
Series Rust abstractions for clk, cpumask, cpufreq, OPP | expand

Commit Message

Viresh Kumar April 11, 2025, 10:55 a.m. UTC 
This implements cpu::from_cpu(), which returns a reference to
Device for a CPU. The C struct is created at initialization time for
CPUs and is never freed and so ARef isn't returned from this function.

The new helper will be used by Rust based cpufreq drivers.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 MAINTAINERS                     |  1 +
 rust/bindings/bindings_helper.h |  1 +
 rust/kernel/cpu.rs              | 31 +++++++++++++++++++++++++++++++
 rust/kernel/lib.rs              |  1 +
 4 files changed, 34 insertions(+)
 create mode 100644 rust/kernel/cpu.rs
diff mbox series

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index 12cde55579a0..475abf72869c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6155,6 +6155,7 @@  F:	include/linux/cpuhotplug.h
 F:	include/linux/smpboot.h
 F:	kernel/cpu.c
 F:	kernel/smpboot.*
+F:	rust/kernel/cpu.rs
 
 CPU IDLE TIME MANAGEMENT FRAMEWORK
 M:	"Rafael J. Wysocki" <rafael@kernel.org>
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index f53d6e1a21f2..ac92c67d2c38 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -11,6 +11,7 @@ 
 #include <linux/blk_types.h>
 #include <linux/blkdev.h>
 #include <linux/clk.h>
+#include <linux/cpu.h>
 #include <linux/cpumask.h>
 #include <linux/cred.h>
 #include <linux/device/faux.h>
diff --git a/rust/kernel/cpu.rs b/rust/kernel/cpu.rs
new file mode 100644
index 000000000000..3054165d3818
--- /dev/null
+++ b/rust/kernel/cpu.rs
@@ -0,0 +1,31 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+//! Generic CPU definitions.
+//!
+//! C header: [`include/linux/cpu.h`](srctree/include/linux/cpu.h)
+
+use crate::{bindings, device::Device, error::Result, prelude::ENODEV};
+
+/// Creates a new instance of CPU's device.
+///
+/// # Safety
+///
+/// Reference counting is not implemented for the CPU device in the C code. When a CPU is
+/// hot-unplugged, the corresponding CPU device is unregistered, but its associated memory
+/// is not freed.
+///
+/// Callers must ensure that the CPU device is not used after it has been unregistered.
+/// This can be achieved, for example, by registering a CPU hotplug notifier and removing
+/// any references to the CPU device within the notifier's callback.
+pub unsafe fn from_cpu(cpu: u32) -> Result<&'static Device> {
+    // SAFETY: The pointer returned by `get_cpu_device()`, if not `NULL`, is a valid pointer to
+    // a `struct device` and is never freed by the C code.
+    let ptr = unsafe { bindings::get_cpu_device(cpu) };
+    if ptr.is_null() {
+        return Err(ENODEV);
+    }
+
+    // SAFETY: The pointer returned by `get_cpu_device()`, if not `NULL`, is a valid pointer to
+    // a `struct device` and is never freed by the C code.
+    Ok(unsafe { Device::as_ref(ptr) })
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index f4dcfefe94be..db372f806875 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -44,6 +44,7 @@ 
 pub mod build_assert;
 #[cfg(CONFIG_COMMON_CLK)]
 pub mod clk;
+pub mod cpu;
 pub mod cpumask;
 pub mod cred;
 pub mod device;