[PATCH v3 14/16] rust: of: add `of::DeviceId` abstraction

[Danilo Krummrich <dakr@kernel.org>]

`of::DeviceId` is an abstraction around `struct of_device_id`.

This is used by subsequent patches, in particular the platform bus
abstractions, to create OF device ID tables.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 MAINTAINERS                     |  1 +
 rust/bindings/bindings_helper.h |  1 +
 rust/kernel/lib.rs              |  1 +
 rust/kernel/of.rs               | 63 +++++++++++++++++++++++++++++++++
 4 files changed, 66 insertions(+)
 create mode 100644 rust/kernel/of.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index d9c512a3e72b..87eb9a7869eb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17340,6 +17340,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git
 F:	Documentation/ABI/testing/sysfs-firmware-ofw
 F:	drivers/of/
 F:	include/linux/of*.h
+F:	rust/kernel/of.rs
 F:	scripts/dtc/
 F:	tools/testing/selftests/dt/
 K:	of_overlay_notifier_
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index cd4edd6496ae..312f03cbdce9 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -15,6 +15,7 @@
 #include <linux/firmware.h>
 #include <linux/jiffies.h>
 #include <linux/mdio.h>
+#include <linux/of_device.h>
 #include <linux/pci.h>
 #include <linux/phy.h>
 #include <linux/refcount.h>
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 3ec690eb6d43..5946f59f1688 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -51,6 +51,7 @@
 pub mod list;
 #[cfg(CONFIG_NET)]
 pub mod net;
+pub mod of;
 pub mod page;
 pub mod prelude;
 pub mod print;
diff --git a/rust/kernel/of.rs b/rust/kernel/of.rs
new file mode 100644
index 000000000000..a37629997974
--- /dev/null
+++ b/rust/kernel/of.rs
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Open Firmware abstractions.
+//!
+//! C header: [`include/linux/of_*.h`](srctree/include/linux/of_*.h)
+
+use crate::{bindings, device_id::RawDeviceId, prelude::*};
+
+/// An open firmware device id.
+#[derive(Clone, Copy)]
+pub struct DeviceId(bindings::of_device_id);
+
+// SAFETY:
+// * `DeviceId` is a `#[repr(transparent)` wrapper of `struct of_device_id` and does not add
+//   additional invariants, so it's safe to transmute to `RawType`.
+// * `DRIVER_DATA_OFFSET` is the offset to the `data` field.
+unsafe impl RawDeviceId for DeviceId {
+    type RawType = bindings::of_device_id;
+
+    const DRIVER_DATA_OFFSET: usize = core::mem::offset_of!(bindings::of_device_id, data);
+
+    fn index(&self) -> usize {
+        self.0.data as _
+    }
+}
+
+impl DeviceId {
+    /// Create a new device id from an OF 'compatible' string.
+    pub const fn new(compatible: &'static CStr) -> Self {
+        let src = compatible.as_bytes_with_nul();
+        // Replace with `bindings::of_device_id::default()` once stabilized for `const`.
+        // SAFETY: FFI type is valid to be zero-initialized.
+        let mut of: bindings::of_device_id = unsafe { core::mem::zeroed() };
+
+        let mut i = 0;
+        while i < src.len() {
+            of.compatible[i] = src[i] as _;
+            i += 1;
+        }
+
+        Self(of)
+    }
+
+    /// The compatible string of the embedded `struct bindings::of_device_id` as `&CStr`.
+    pub fn compatible<'a>(&self) -> &'a CStr {
+        // SAFETY: `self.compatible` is a valid `char` pointer.
+        unsafe { CStr::from_char_ptr(self.0.compatible.as_ptr()) }
+    }
+}
+
+/// Create an OF `IdTable` with an "alias" for modpost.
+#[macro_export]
+macro_rules! of_device_table {
+    ($table_name:ident, $module_table_name:ident, $id_info_type: ty, $table_data: expr) => {
+        const $table_name: $crate::device_id::IdArray<
+            $crate::of::DeviceId,
+            $id_info_type,
+            { $table_data.len() },
+        > = $crate::device_id::IdArray::new($table_data);
+
+        $crate::module_device_table!("of", $module_table_name, $table_name);
+    };
+}
-- 
2.46.2