[PATCH v6 2/6] rust: driver: Consolidate `Adapter::of_id_info` methods using `#[cfg]`

[Igor Korotin <igor.korotin.linux@gmail.com>]

Refactor the `of_id_info` methods in the `Adapter` trait to reduce
duplication. Previously, the method had two versions selected
via `#[cfg(...)]` and `#[cfg(not(...))]`. This change merges them into a
single method by using `#[cfg]` blocks within the method body.

Suggested-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Igor Korotin <igor.korotin.linux@gmail.com>
---
 rust/kernel/driver.rs | 40 +++++++++++++++++++++-------------------
 1 file changed, 21 insertions(+), 19 deletions(-)

diff --git a/rust/kernel/driver.rs b/rust/kernel/driver.rs
index ec9166cedfa7..cb62b75a0c0e 100644
--- a/rust/kernel/driver.rs
+++ b/rust/kernel/driver.rs
@@ -147,30 +147,32 @@ pub trait Adapter {
     /// 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()?;
+        #[cfg(not(CONFIG_OF))]
+        {
+            let _ = dev;
+            return None;
+        }
 
-        // 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()) };
+        #[cfg(CONFIG_OF)]
+        {
+            let table = Self::of_id_table()?;
 
-        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>() };
+            // 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()) };
 
-            Some(table.info(<of::DeviceId as crate::device_id::RawDeviceId>::index(id)))
-        }
-    }
+            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>() };
 
-    #[cfg(not(CONFIG_OF))]
-    #[allow(missing_docs)]
-    fn of_id_info(_dev: &device::Device) -> Option<&'static Self::IdInfo> {
-        None
+                Some(table.info(<of::DeviceId as crate::device_id::RawDeviceId>::index(id)))
+            }
+        }
     }
 
     /// Returns the driver's private data from the matching entry of any of the ID tables, if any.
-- 
2.43.0