linux-kernel - [PATCH] rust: time: New module for timekeeping functions

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Message-Id: <20230221-gpu-up-time-v1-1-bf8fe74b7f55@asahilina.net>
Date:   Tue, 21 Feb 2023 16:06:36 +0900
From:   Asahi Lina <lina@...hilina.net>
To:     Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        John Stultz <jstultz@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
        asahi@...ts.linux.dev, Asahi Lina <lina@...hilina.net>
Subject: [PATCH] rust: time: New module for timekeeping functions

This module is intended to contain functions related to kernel
timekeeping and time. Initially, this just wraps ktime_get() and
ktime_get_boottime() and returns them as core::time::Duration instances.
This is useful for drivers that need to implement simple retry loops and
timeouts.

Signed-off-by: Asahi Lina <lina@...hilina.net>
---
 rust/bindings/bindings_helper.h |  4 +++-
 rust/kernel/lib.rs              |  1 +
 rust/kernel/time.rs             | 25 +++++++++++++++++++++++++
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 75d85bd6c592..587f3d1c0c9f 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -6,8 +6,10 @@
  * Sorted alphabetically.
  */
 
-#include <linux/slab.h>
+#include <linux/ktime.h>
 #include <linux/refcount.h>
+#include <linux/slab.h>
+#include <linux/timekeeping.h>
 
 /* `bindgen` gets confused at certain things. */
 const gfp_t BINDINGS_GFP_KERNEL = GFP_KERNEL;
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 223564f9f0cc..371b1b17570e 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -37,6 +37,7 @@ mod static_assert;
 pub mod std_vendor;
 pub mod str;
 pub mod sync;
+pub mod time;
 pub mod types;
 
 #[doc(hidden)]
diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs
new file mode 100644
index 000000000000..02844db47d34
--- /dev/null
+++ b/rust/kernel/time.rs
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Timekeeping functions.
+//!
+//! C header: [`include/linux/ktime.h`](../../../../include/linux/ktime.h)
+//! C header: [`include/linux/timekeeping.h`](../../../../include/linux/timekeeping.h)
+
+use crate::bindings;
+use core::time::Duration;
+
+/// Returns the kernel time elapsed since boot, excluding time spent sleeping, as a [`Duration`].
+pub fn ktime_get() -> Duration {
+    // SAFETY: Function has no side effects and no inputs.
+    Duration::from_nanos(unsafe { bindings::ktime_get() }.try_into().unwrap())
+}
+
+/// Returns the kernel time elapsed since boot, including time spent sleeping, as a [`Duration`].
+pub fn ktime_get_boottime() -> Duration {
+    Duration::from_nanos(
+        // SAFETY: Function has no side effects and no variable inputs.
+        unsafe { bindings::ktime_get_with_offset(bindings::tk_offsets_TK_OFFS_BOOT) }
+            .try_into()
+            .unwrap(),
+    )
+}

---
base-commit: 89f5349e0673322857bd432fa23113af56673739
change-id: 20230221-gpu-up-time-ea9412204c3b

Thank you,
~~ Lina