rust: of: Add OF node abstraction

This abstraction enables Rust drivers to walk Device Tree nodes and
query their properties.

Signed-off-by: Asahi Lina <lina@asahilina.net>

rust/bindings/bindings_helper.h

@@ -10,6 +10,9 @@
 #include <linux/device.h>
 #include <linux/io-pgtable.h>
 #include <linux/ktime.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/refcount.h>
 #include <linux/wait.h>

rust/helpers.c

@@ -337,6 +337,20 @@ const struct of_device_id *rust_helper_of_match_device(
 }
 EXPORT_SYMBOL_GPL(rust_helper_of_match_device);
 
+bool rust_helper_of_node_is_root(const struct device_node *np)
+{
+	return of_node_is_root(np);
+}
+EXPORT_SYMBOL_GPL(rust_helper_of_node_is_root);
+
+struct device_node *rust_helper_of_parse_phandle(const struct device_node *np,
+		const char *phandle_name,
+		int index)
+{
+	return of_parse_phandle(np, phandle_name, index);
+}
+EXPORT_SYMBOL_GPL(rust_helper_of_parse_phandle);
+
 /*
  * We use `bindgen`'s `--size_t-is-usize` option to bind the C `size_t` type
  * as the Rust `usize` type, so we can use it in contexts where Rust

rust/kernel/device.rs

@@ -8,7 +8,7 @@ use crate::{
     bindings,
     error::Result,
     macros::pin_data,
-    pin_init, pr_crit,
+    of, pin_init, pr_crit,
     str::CStr,
     sync::{lock::mutex, lock::Guard, LockClassKey, Mutex, UniqueArc},
 };
@@ -52,6 +52,13 @@ pub unsafe trait RawDevice {
         unsafe { CStr::from_char_ptr(name) }
     }
 
+    /// Gets the OpenFirmware node attached to this device
+    fn of_node(&self) -> Option<of::Node> {
+        let ptr = self.raw_device();
+
+        unsafe { of::Node::get_from_raw((*ptr).of_node) }
+    }
+
     /// Prints an emergency-level message (level 0) prefixed with device information.
     ///
     /// More details are available from [`dev_emerg`].