[PATCH v6 13/16] rust: driver: implement `Adapter`

[Danilo Krummrich <dakr@kernel.org>]

In order to not duplicate code in bus specific implementations (e.g.
platform), implement a generic `driver::Adapter` to represent the
connection of matched drivers and devices.

Bus specific `Adapter` implementations can simply implement this trait
to inherit generic functionality, such as matching OF or ACPI device IDs
and ID table entries.

Suggested-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/bindings/bindings_helper.h |  1 +
 rust/kernel/driver.rs           | 59 ++++++++++++++++++++++++++++++++-
 2 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 6d7a68e2ecb7..8fe70183a392 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -20,6 +20,7 @@
 #include <linux/jump_label.h>
 #include <linux/mdio.h>
 #include <linux/miscdevice.h>
+#include <linux/of_device.h>
 #include <linux/pci.h>
 #include <linux/phy.h>
 #include <linux/pid_namespace.h>
diff --git a/rust/kernel/driver.rs b/rust/kernel/driver.rs
index c1957ee7bb7e..63dbebbc0829 100644
--- a/rust/kernel/driver.rs
+++ b/rust/kernel/driver.rs
@@ -6,7 +6,9 @@
 //! register using the [`Registration`] class.
 
 use crate::error::{Error, Result};
-use crate::{init::PinInit, str::CStr, try_pin_init, types::Opaque, ThisModule};
+use crate::{
+    device, device_id, init::PinInit, of, str::CStr, try_pin_init, types::Opaque, ThisModule,
+};
 use core::pin::Pin;
 use macros::{pin_data, pinned_drop};
 
@@ -115,3 +117,58 @@ fn init(
         }
     }
 }
+
+/// The bus independent adapter to match a drivers and a devices.
+///
+/// This trait should be implemented by the bus specific adapter, which represents the connection
+/// of a device and a driver.
+///
+/// It provides bus independent functions for device / driver interactions.
+pub trait Adapter {
+    /// The type holding driver private data about each device id supported by the driver.
+    type IdInfo: 'static;
+
+    /// The [`of::IdTable`] of the corresponding driver.
+    fn of_id_table() -> Option<of::IdTable<Self::IdInfo>>;
+
+    /// Returns the driver's private data from the matching entry in the [`of::IdTable`], if any.
+    ///
+    /// If this returns `None`, it means there is no match with an entry in the [`of::IdTable`].
+    #[cfg(CONFIG_OF)]
+    fn of_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
+        let table = Self::of_id_table()?;
+
+        // SAFETY:
+        // - `table` has static lifetime, hence it's valid for read,
+        // - `dev` is guaranteed to be valid while it's alive, and so is `pdev.as_ref().as_raw()`.
+        let raw_id = unsafe { bindings::of_match_device(table.as_ptr(), dev.as_raw()) };
+
+        if raw_id.is_null() {
+            None
+        } else {
+            // SAFETY: `DeviceId` is a `#[repr(transparent)` wrapper of `struct of_device_id` and
+            // does not add additional invariants, so it's safe to transmute.
+            let id = unsafe { &*raw_id.cast::<of::DeviceId>() };
+
+            Some(table.info(<of::DeviceId as device_id::RawDeviceId>::index(id)))
+        }
+    }
+
+    #[cfg(not(CONFIG_OF))]
+    fn of_id_info(_dev: &device::Device) -> Option<&'static Self::IdInfo> {
+        None
+    }
+
+    /// Returns the driver's private data from the matching entry of any of the ID tables, if any.
+    ///
+    /// If this returns `None`, it means that there is no match in any of the ID tables directly
+    /// associated with a [`device::Device`].
+    fn id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
+        let id = Self::of_id_info(dev);
+        if id.is_some() {
+            return id;
+        }
+
+        None
+    }
+}
-- 
2.47.1