[PATCH v2 04/25] rust: driver: make Adapter trait lifetime-parameterized

[Danilo Krummrich]

Parameterize the Adapter trait with a lifetime, changing the id_info(),
of_id_info() and acpi_id_info() methods to take &'bound Device<Bound> and
return &'bound Self::IdInfo instead of &'static.

This is needed for the ForLt conversion of bus driver traits. Once
Driver becomes lifetime-parameterized, its IdInfo associated type may
depend on the lifetime parameter. With Adapter<'bound>, the impl can set
IdInfo = <F::Of<'bound> as Driver<'bound>>::IdInfo and the lifetime flows
through naturally, avoiding the need for transmute.

For the current non-lifetime-parameterized Driver trait, this is a no-op
type relaxation; IdInfo is 'static and &'static coerces to &'bound.

Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
---
 rust/kernel/driver.rs   | 16 ++++++++++------
 rust/kernel/i2c.rs      | 10 +++++-----
 rust/kernel/platform.rs |  4 ++--
 3 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/rust/kernel/driver.rs b/rust/kernel/driver.rs
index 2ab3c0050117..e462535f545d 100644
--- a/rust/kernel/driver.rs
+++ b/rust/kernel/driver.rs
@@ -96,7 +96,11 @@
 
 use crate::{
     acpi,
-    device,
+    device::{
+        self,
+        Bound,
+        Device, //
+    },
     of,
     prelude::*,
     types::{
@@ -192,7 +196,7 @@ extern "C" fn post_unbind_callback(dev: *mut bindings::device) {
         // a `struct device`.
         //
         // INVARIANT: `dev` is valid for the duration of the `post_unbind_callback()`.
-        let dev = unsafe { &*dev.cast::<device::Device<device::CoreInternal>>() };
+        let dev = unsafe { &*dev.cast::<Device<device::CoreInternal>>() };
 
         // `remove()` has been completed at this point; devres resources are still valid and will
         // be released after the driver's bus device private data is dropped.
@@ -309,7 +313,7 @@ unsafe fn acpi_of_match_device(
 /// of a device and a driver.
 ///
 /// It provides bus independent functions for device / driver interactions.
-pub trait Adapter {
+pub trait Adapter<'bound> {
     /// The type holding driver private data about each device id supported by the driver.
     type IdInfo: 'static;
 
@@ -319,7 +323,7 @@ pub trait Adapter {
     /// Returns the driver's private data from the matching entry in the [`acpi::IdTable`], if any.
     ///
     /// If this returns `None`, it means there is no match with an entry in the [`acpi::IdTable`].
-    fn acpi_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
+    fn acpi_id_info(dev: &'bound Device<Bound>) -> Option<&'bound Self::IdInfo> {
         #[cfg(not(CONFIG_ACPI))]
         {
             let _ = dev;
@@ -353,7 +357,7 @@ fn acpi_id_info(dev: &device::Device) -> Option<&'static 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`].
-    fn of_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
+    fn of_id_info(dev: &'bound Device<Bound>) -> Option<&'bound Self::IdInfo> {
         let table = Self::of_id_table()?;
 
         #[cfg(not(any(CONFIG_OF, CONFIG_ACPI)))]
@@ -417,7 +421,7 @@ fn of_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
     ///
     /// 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> {
+    fn id_info(dev: &'bound Device<Bound>) -> Option<&'bound Self::IdInfo> {
         let id = Self::acpi_id_info(dev);
         if id.is_some() {
             return id;
diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
index cde3dd7a6cc7..208c73aa3ce3 100644
--- a/rust/kernel/i2c.rs
+++ b/rust/kernel/i2c.rs
@@ -162,8 +162,8 @@ extern "C" fn probe_callback(idev: *mut bindings::i2c_client) -> kernel::ffi::c_
         // INVARIANT: `idev` is valid for the duration of `probe_callback()`.
         let idev = unsafe { &*idev.cast::<I2cClient<device::CoreInternal>>() };
 
-        let info =
-            Self::i2c_id_info(idev).or_else(|| <Self as driver::Adapter>::id_info(idev.as_ref()));
+        let info = Self::i2c_id_info(idev)
+            .or_else(|| <Self as driver::Adapter<'_>>::id_info(idev.as_ref()));
 
         from_result(|| {
             let data = T::probe(idev, info);
@@ -198,14 +198,14 @@ extern "C" fn shutdown_callback(idev: *mut bindings::i2c_client) {
     }
 
     /// The [`i2c::IdTable`] of the corresponding driver.
-    fn i2c_id_table() -> Option<IdTable<<Self as driver::Adapter>::IdInfo>> {
+    fn i2c_id_table() -> Option<IdTable<<Self as driver::Adapter<'static>>::IdInfo>> {
         T::I2C_ID_TABLE
     }
 
     /// Returns the driver's private data from the matching entry in the [`i2c::IdTable`], if any.
     ///
     /// If this returns `None`, it means there is no match with an entry in the [`i2c::IdTable`].
-    fn i2c_id_info(dev: &I2cClient) -> Option<&'static <Self as driver::Adapter>::IdInfo> {
+    fn i2c_id_info(dev: &I2cClient) -> Option<&'static <Self as driver::Adapter<'static>>::IdInfo> {
         let table = Self::i2c_id_table()?;
 
         // SAFETY:
@@ -225,7 +225,7 @@ fn i2c_id_info(dev: &I2cClient) -> Option<&'static <Self as driver::Adapter>::Id
     }
 }
 
-impl<T: Driver + 'static> driver::Adapter for Adapter<T> {
+impl<'bound, T: Driver + 'static> driver::Adapter<'bound> for Adapter<T> {
     type IdInfo = T::IdInfo;
 
     fn of_id_table() -> Option<of::IdTable<Self::IdInfo>> {
diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index 7ff69e3eea90..506731a648c2 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs
@@ -101,7 +101,7 @@ extern "C" fn probe_callback(pdev: *mut bindings::platform_device) -> kernel::ff
         //
         // INVARIANT: `pdev` is valid for the duration of `probe_callback()`.
         let pdev = unsafe { &*pdev.cast::<Device<device::CoreInternal>>() };
-        let info = <Self as driver::Adapter>::id_info(pdev.as_ref());
+        let info = <Self as driver::Adapter<'_>>::id_info(pdev.as_ref());
 
         from_result(|| {
             let data = T::probe(pdev, info);
@@ -127,7 +127,7 @@ extern "C" fn remove_callback(pdev: *mut bindings::platform_device) {
     }
 }
 
-impl<T: Driver + 'static> driver::Adapter for Adapter<T> {
+impl<'bound, T: Driver + 'static> driver::Adapter<'bound> for Adapter<T> {
     type IdInfo = T::IdInfo;
 
     fn of_id_table() -> Option<of::IdTable<Self::IdInfo>> {
-- 
2.54.0