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>

Author: hoshinolina

rust/bindings/bindings_helper.h

@@ -57,6 +57,8 @@
 #include <linux/jump_label.h>
 #include <linux/mdio.h>
 #include <linux/miscdevice.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
 #include <linux/of_device.h>
 #include <linux/pci.h>
 #include <linux/phy.h>

rust/helpers/helpers.c

@@ -28,6 +28,7 @@
 #include "kunit.c"
 #include "mm.c"
 #include "mutex.c"
+#include "of.c"
 #include "page.c"
 #include "platform.c"
 #include "pci.c"

rust/helpers/of.c

@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/of.h>
+#include <linux/of_device.h>
+
+const struct of_device_id *rust_helper_of_match_device(
+		const struct of_device_id *matches, const struct device *dev)
+{
+			return of_match_device(matches, dev);
+}
+
+#ifdef CONFIG_OF
+bool rust_helper_of_node_is_root(const struct device_node *np)
+{
+	return of_node_is_root(np);
+}
+#endif
+
+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);
+}

rust/kernel/device.rs

@@ -7,6 +7,7 @@
 use crate::{
     bindings,
     error::{code::*, Error, Result},
+    of,
     str::CStr,
     types::{ARef, NotThreadSafe, Opaque},
 };
@@ -102,6 +103,13 @@ impl<Ctx: DeviceContext> Device<Ctx> {
         unsafe { &*ptr.cast() }
     }
 
+    /// Gets the OpenFirmware node attached to this device
+    pub fn of_node(&self) -> Option<of::Node> {
+        let ptr = self.0.get();
+        // SAFETY: This is safe as long as of_node is NULL or valid.
+        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`].