[PATCH v3 1/4] rust: sync: Add i8/i16 atomic_load_acquire/atomic_store_release helpers

[FUJITA Tomonori <fujita.tomonori@gmail.com>]

Add helper functions to expose smp_load_acquire() and
smp_store_release() for i8 and i16 types.

The smp_load_acquire() and smp_store_release() macros require type
information (sizeof) to generate appropriate architecture-specific
memory ordering instructions. Therefore, separate helper functions are
needed for each type size.

These helpers expose different symbol names than their C counterparts
so they are split into atomic_ext.c instead of atomic.c. The symbol
names; atomic_[i8|i16]_load_acquire and atomic_[i8|i16]_store_release
makes the interface Rust/C clear, consistent with i32/i64.

These helpers will be used by the upcoming Atomic<i8> and Atomic<i16>
implementation to provide proper Acquire/Release semantics across all
architectures.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 rust/helpers/atomic_ext.c | 23 +++++++++++++++++++++++
 rust/helpers/helpers.c    |  1 +
 2 files changed, 24 insertions(+)
 create mode 100644 rust/helpers/atomic_ext.c

diff --git a/rust/helpers/atomic_ext.c b/rust/helpers/atomic_ext.c
new file mode 100644
index 000000000000..a10c723ab224
--- /dev/null
+++ b/rust/helpers/atomic_ext.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <asm/barrier.h>
+
+__rust_helper s8 rust_helper_atomic_i8_load_acquire(s8 *ptr)
+{
+	return smp_load_acquire(ptr);
+}
+
+__rust_helper s16 rust_helper_atomic_i16_load_acquire(s16 *ptr)
+{
+	return smp_load_acquire(ptr);
+}
+
+__rust_helper void rust_helper_atomic_i8_store_release(s8 *ptr, s8 val)
+{
+	smp_store_release(ptr, val);
+}
+
+__rust_helper void rust_helper_atomic_i16_store_release(s16 *ptr, s16 val)
+{
+	smp_store_release(ptr, val);
+}
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 79c72762ad9c..15d75578f459 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -8,6 +8,7 @@
  */
 
 #include "atomic.c"
+#include "atomic_ext.c"
 #include "auxiliary.c"
 #include "barrier.c"
 #include "binder.c"
-- 
2.43.0