linux-kernel - [PATCH] rust: acpi: add `acpi::DeviceId` abstraction

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Message-ID: <20250530123815.1766726-1-igor.korotin.linux@gmail.com>
Date: Fri, 30 May 2025 13:38:06 +0100
From: Igor Korotin <igor.korotin.linux@...il.com>
To: "Rafael J . Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>
Cc: Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	linux-acpi@...r.kernel.org,
	rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Igor Korotin <igor.korotin.linux@...il.com>
Subject: [PATCH] rust: acpi: add `acpi::DeviceId` abstraction

`acpi::DeviceId` is an abstraction around `struct acpi_device_id`.

This is used by subsequent patches, in particular the i2c driver
abstractions, to create ACPI device ID tables.

Signed-off-by: Igor Korotin <igor.korotin.linux@...il.com>
---
 MAINTAINERS         |  1 +
 rust/kernel/acpi.rs | 63 +++++++++++++++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs  |  1 +
 3 files changed, 65 insertions(+)
 create mode 100644 rust/kernel/acpi.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index b659fb27ab63..5f8dfae08454 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -302,6 +302,7 @@ F:	include/linux/acpi.h
 F:	include/linux/fwnode.h
 F:	include/linux/fw_table.h
 F:	lib/fw_table.c
+F:	rust/kernel/acpi.rs
 F:	tools/power/acpi/
 
 ACPI APEI
diff --git a/rust/kernel/acpi.rs b/rust/kernel/acpi.rs
new file mode 100644
index 000000000000..bbd38910736c
--- /dev/null
+++ b/rust/kernel/acpi.rs
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Advanced Configuration and Power Interface abstractions.
+
+use crate::{bindings, device_id::RawDeviceId, prelude::*};
+
+/// IdTable type for ACPI drivers.
+pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>;
+
+/// An ACPI device id.
+#[repr(transparent)]
+#[derive(Clone, Copy)]
+pub struct DeviceId(bindings::acpi_device_id);
+
+// SAFETY:
+// * `DeviceId` is a `#[repr(transparent)` wrapper of `struct acpi_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::acpi_device_id;
+
+    const DRIVER_DATA_OFFSET: usize = core::mem::offset_of!(bindings::acpi_device_id, driver_data);
+
+    fn index(&self) -> usize {
+        self.0.driver_data as _
+    }
+}
+
+impl DeviceId {
+    const ACPI_ID_LEN: usize = 16;
+
+    /// Create a new device id from an ACPI 'id' string.
+    pub const fn new(id: &'static CStr) -> Self {
+        assert!(id.len() <= Self::ACPI_ID_LEN, "ID exceeds 16 bytes");
+        let src = id.as_bytes_with_nul();
+        // Replace with `bindings::acpi_device_id::default()` once stabilized for `const`.
+        // SAFETY: FFI type is valid to be zero-initialized.
+        let mut acpi: bindings::acpi_device_id = unsafe { core::mem::zeroed() };
+        // TODO: Use `clone_from_slice` once the corresponding types do match.
+        let mut i = 0;
+        while i < src.len() {
+            acpi.id[i] = src[i] as _;
+            i += 1;
+        }
+
+        Self(acpi)
+    }
+}
+
+/// Create an ACPI `IdTable` with an "alias" for modpost.
+#[macro_export]
+macro_rules! acpi_device_table {
+    ($table_name:ident, $module_table_name:ident, $id_info_type: ty, $table_data: expr) => {
+        const $table_name: $crate::device_id::IdArray<
+            $crate::acpi::DeviceId,
+            $id_info_type,
+            { $table_data.len() },
+        > = $crate::device_id::IdArray::new($table_data);
+
+        $crate::module_device_table!("acpi", $module_table_name, $table_name);
+    };
+}
+
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 15c5f72976cd..05f1d3870bf7 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -78,6 +78,7 @@
 #[cfg(CONFIG_NET)]
 pub mod net;
 pub mod of;
+pub mod acpi;
 pub mod page;
 #[cfg(CONFIG_I2C)]
 pub mod i2c;
-- 
2.43.0