[PATCH v2 2/2] rust: kernel: of: Add overlay id abstraction

[Ayush Singh]

Allow applying devicetree overlays from Rust.

The overlay is removed on Drop.

Signed-off-by: Ayush Singh <ayush@xxxxxxxxxxxxxxx>
---
 rust/kernel/of.rs | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/rust/kernel/of.rs b/rust/kernel/of.rs
index 74d42dce06f0e9f67a0e5bd1287117b4966d4af9..646148cc959fd5414271f9cf9023ef5d77a2ac2c 100644
--- a/rust/kernel/of.rs
+++ b/rust/kernel/of.rs
@@ -75,3 +75,37 @@ pub fn as_raw(&self) -> *mut bindings::device_node {
         self.0.get()
     }
 }
+
+/// Devicetree overlay present in livetree.
+///
+/// The overlay is removed on Drop
+pub struct OvcsId(kernel::ffi::c_int);
+
+impl OvcsId {
+    /// Create and apply an overlay changeset to the live tree.
+    pub fn of_overlay_fdt_apply(overlay: &[u8], base: &DeviceNode) -> Result<Self> {
+        let mut ovcs_id: kernel::ffi::c_int = 0;
+
+        // Ensure that overlay length fits in u32
+        let Ok(overlay_len) = overlay.len().try_into() else {
+            return Err(crate::error::code::E2BIG);
+        };
+
+        crate::error::to_result(unsafe {
+            bindings::of_overlay_fdt_apply(
+                overlay.as_ptr().cast(),
+                overlay_len,
+                &mut ovcs_id,
+                base.as_raw(),
+            )
+        })?;
+
+        Ok(Self(ovcs_id))
+    }
+}
+
+impl Drop for OvcsId {
+    fn drop(&mut self) {
+        unsafe { bindings::of_overlay_remove(&mut self.0) };
+    }
+}

-- 
2.50.1