[PATCH v6] rust: ACPI: fix missing match data for PRP0001

[Markus Probst <markus.probst@posteo.de>]

Export `acpi_of_match_device` function and use it to match the of device
table against ACPI PRP0001 in Rust.

This fixes id_info being None on ACPI PRP0001 devices.

Using `device_get_match_data` is not possible, because Rust stores an
index in the of device id instead of a data pointer. This was done this
way to provide a convenient and obvious API for drivers, which can be
evaluated in const context without the use of any unstable language
features.

Fixes: 7a718a1f26d1 ("rust: driver: implement `Adapter`")
Signed-off-by: Markus Probst <markus.probst@posteo.de>
---
Changes in v6:
- rebased onto v7.1-rc1
- Link to v5: https://patch.msgid.link/20260420-rust_acpi_prp0001-v5-1-f77869b18b9f@posteo.de

Changes in v5:
- provide a stub instead of canditionalize the caller
- Link to v4: https://lore.kernel.org/r/20260408-rust_acpi_prp0001-v4-1-87b78ad79239@posteo.de

Changes in v4:
- fix compilation on !CONFIG_ACPI
- fix typo
- add doc to `acpi_of_match_device` and remove from header file include
- Link to v3: https://lore.kernel.org/r/20260407-rust_acpi_prp0001-v3-1-c5b24590c273@posteo.de

Changes in v3:
- use acpi/acpi_bus.h instead of drivers/acpi/internal.h to declare
  `acpi_of_match_device`
- Link to v2: https://lore.kernel.org/r/20260405-rust_acpi_prp0001-v2-1-4f8b1cf075d3@posteo.de

Changes in v2:
- keep unsafe block as short as possible
- don't export acpi_of_match_device
- add implementation decisions to commit msg
- Link to v1: https://lore.kernel.org/r/20260401-rust_acpi_prp0001-v1-1-f6a4d2ef9244@posteo.de
---
 MAINTAINERS             |  1 +
 drivers/acpi/bus.c      |  6 ++--
 include/acpi/acpi_bus.h | 11 ++++++++
 rust/helpers/acpi.c     | 16 +++++++++++
 rust/helpers/helpers.c  |  1 +
 rust/kernel/driver.rs   | 74 ++++++++++++++++++++++++++++++++++++++++---------
 6 files changed, 93 insertions(+), 16 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index 2fb1c75afd16..4367a303e90e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -291,6 +291,7 @@ F:	include/linux/acpi.h
 F:	include/linux/fwnode.h
 F:	include/linux/fw_table.h
 F:	lib/fw_table.c
+F:	rust/helpers/acpi.c
 F:	rust/kernel/acpi.rs
 F:	tools/power/acpi/
 
diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index 2ec095e2009e..554dbddb1c8c 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -831,9 +831,9 @@ const struct acpi_device *acpi_companion_match(const struct device *dev)
  * identifiers and a _DSD object with the "compatible" property, use that
  * property to match against the given list of identifiers.
  */
-static bool acpi_of_match_device(const struct acpi_device *adev,
-				 const struct of_device_id *of_match_table,
-				 const struct of_device_id **of_id)
+bool acpi_of_match_device(const struct acpi_device *adev,
+			  const struct of_device_id *of_match_table,
+			  const struct of_device_id **of_id)
 {
 	const union acpi_object *of_compatible, *obj;
 	int i, nval;
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index b701b5f972cb..c85f7d8f1632 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -187,6 +187,10 @@ struct acpi_driver {
  * -----------
  */
 
+bool acpi_of_match_device(const struct acpi_device *adev,
+			  const struct of_device_id *of_match_table,
+			  const struct of_device_id **of_id);
+
 /* Status (_STA) */
 
 struct acpi_device_status {
@@ -992,6 +996,13 @@ int acpi_scan_add_dep(acpi_handle handle, struct acpi_handle_list *dep_devices);
 u32 arch_acpi_add_auto_dep(acpi_handle handle);
 #else	/* CONFIG_ACPI */
 
+static inline bool acpi_of_match_device(const struct acpi_device *adev,
+					const struct of_device_id *of_match_table,
+					const struct of_device_id **of_id)
+{
+	return false;
+}
+
 static inline int register_acpi_bus_type(void *bus) { return 0; }
 static inline int unregister_acpi_bus_type(void *bus) { return 0; }
 
diff --git a/rust/helpers/acpi.c b/rust/helpers/acpi.c
new file mode 100644
index 000000000000..e75c9807bbad
--- /dev/null
+++ b/rust/helpers/acpi.c
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/acpi.h>
+#include <acpi/acpi_bus.h>
+
+__rust_helper bool rust_helper_acpi_of_match_device(const struct acpi_device *adev,
+						    const struct of_device_id *of_match_table,
+						    const struct of_device_id **of_id)
+{
+	return acpi_of_match_device(adev, of_match_table, of_id);
+}
+
+__rust_helper struct acpi_device *rust_helper_to_acpi_device_node(struct fwnode_handle *fwnode)
+{
+	return to_acpi_device_node(fwnode);
+}
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 625921e27dfb..38b34518eff1 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -38,6 +38,7 @@
 #define __rust_helper __always_inline
 #endif
 
+#include "acpi.c"
 #include "atomic.c"
 #include "atomic_ext.c"
 #include "auxiliary.c"
diff --git a/rust/kernel/driver.rs b/rust/kernel/driver.rs
index 36de8098754d..93e5dd6ae371 100644
--- a/rust/kernel/driver.rs
+++ b/rust/kernel/driver.rs
@@ -278,6 +278,26 @@ fn init(
     }
 }
 
+// Calling the FFI function directly from the `Adapter` impl may result in it being called
+// directly from driver modules. This happens since the Rust compiler will use monomorphisation, so
+// it might happen that functions are instantiated within the calling driver module. For now, work
+// around this with `#[inline(never)]` helpers.
+//
+// TODO: Remove once a more generic solution has been implemented. For instance, we may be able to
+// leverage `bindgen` to take care of this depending on whether a symbol is (already) exported.
+#[inline(never)]
+#[allow(clippy::missing_safety_doc)]
+#[allow(dead_code)]
+#[must_use]
+unsafe fn acpi_of_match_device(
+    adev: *const bindings::acpi_device,
+    of_match_table: *const bindings::of_device_id,
+    of_id: *mut *const bindings::of_device_id,
+) -> bool {
+    // SAFETY: Safety requirements are the same as `bindings::acpi_of_match_device`.
+    unsafe { bindings::acpi_of_match_device(adev, of_match_table, of_id) }
+}
+
 /// 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
@@ -329,35 +349,63 @@ fn acpi_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
     ///
     /// 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> {
-        #[cfg(not(CONFIG_OF))]
+        let table = Self::of_id_table()?;
+
+        #[cfg(not(any(CONFIG_OF, CONFIG_ACPI)))]
         {
-            let _ = dev;
-            None
+            let _ = (dev, table);
         }
 
         #[cfg(CONFIG_OF)]
         {
-            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 `dev.as_raw()`.
             let raw_id = unsafe { bindings::of_match_device(table.as_ptr(), dev.as_raw()) };
 
-            if raw_id.is_null() {
-                None
-            } else {
+            if !raw_id.is_null() {
                 // 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 crate::device_id::RawDeviceIdIndex>::index(
-                        id,
-                    )),
-                )
+                return Some(table.info(
+                    <of::DeviceId as crate::device_id::RawDeviceIdIndex>::index(id),
+                ));
             }
         }
+
+        #[cfg(CONFIG_ACPI)]
+        {
+            use core::ptr;
+            use device::property::FwNode;
+
+            let mut raw_id = ptr::null();
+
+            let fwnode = dev.fwnode().map_or(ptr::null_mut(), FwNode::as_raw);
+
+            // SAFETY: `fwnode` is a pointer to a valid `fwnode_handle`. A null pointer will be
+            // passed through the function.
+            let adev = unsafe { bindings::to_acpi_device_node(fwnode) };
+
+            // SAFETY:
+            // - `adev` is a valid pointer to `acpi_device` or is null. It is guaranteed to be
+            //   valid as long as `dev` is alive.
+            // - `table` has static lifetime, hence it's valid for read.
+            if unsafe { acpi_of_match_device(adev, table.as_ptr(), &raw mut raw_id) } {
+                // SAFETY:
+                // - the function returns true, therefore `raw_id` has been set to a pointer to a
+                //   valid `of_device_id`.
+                // - `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>() };
+
+                return Some(table.info(
+                    <of::DeviceId as crate::device_id::RawDeviceIdIndex>::index(id),
+                ));
+            }
+        }
+
+        None
     }
 
     /// Returns the driver's private data from the matching entry of any of the ID tables, if any.

---
base-commit: 3131ff5a117498bb4b9db3a238bb311cbf8383ce
change-id: 20260401-rust_acpi_prp0001-a2971543b555