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

@@ -65,6 +65,8 @@
 #include <linux/mdio.h>
 #include <linux/mm.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/of.c

@@ -1,8 +1,29 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/of.h>
+#include <linux/of_device.h>
 
 bool rust_helper_is_of_node(const struct fwnode_handle *fwnode)
 {
 	return is_of_node(fwnode);
 }
+
+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

@@ -4,6 +4,7 @@
 //!
 //! C header: [`include/linux/device.h`](srctree/include/linux/device.h)
 
+use crate::of;
 use crate::{
     bindings, fmt,
     prelude::*,
@@ -368,6 +369,13 @@ 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`].