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linux/rust/helpers/time.c
FUJITA Tomonori 1b7bbd5975 rust: time: Avoid 64-bit integer division on 32-bit architectures
Avoid 64-bit integer division that 32-bit architectures don't
implement generally. This uses ktime_to_us() and ktime_to_ms()
instead.

The time abstraction needs i64 / u32 division so C's div_s64() can be
used but ktime_to_us() and ktime_to_ms() provide a simpler solution
for this time abstraction problem on 32-bit architectures.

32-bit ARM is the only 32-bit architecture currently supported by
Rust. Using the cfg attribute, only 32-bit architectures will call
ktime_to_us() and ktime_to_ms(), while the other 64-bit architectures
will continue to use the current code as-is to avoid the overhead.

One downside of calling the C's functions is that the as_micros/millis
methods can no longer be const fn. We stick with the simpler approach
unless there's a compelling need for a const fn.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Link: https://lore.kernel.org/r/20250502004524.230553-1-fujita.tomonori@gmail.com
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
2025-06-16 15:01:15 +02:00

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C

// SPDX-License-Identifier: GPL-2.0
#include <linux/ktime.h>
s64 rust_helper_ktime_to_us(const ktime_t kt)
{
return ktime_to_us(kt);
}
s64 rust_helper_ktime_to_ms(const ktime_t kt)
{
return ktime_to_ms(kt);
}