Re: [PATCH v2 3/5] rust: driver: Add ACPI id table support to Adapter trait

[Danilo Krummrich <dakr@kernel.org>]

On Thu, Jun 05, 2025 at 05:27:26PM +0100, Igor Korotin wrote:
> From: Igor Korotin <igor.korotin.linux@gmail.com>
> 
> Extend the `Adapter` trait to support ACPI device identification.
> 
> This mirrors the existing Open Firmware (OF) support (`of_id_table`) and
> enables Rust drivers to match and retrieve ACPI-specific device data
> when `CONFIG_ACPI` is enabled.
> 
> To avoid breaking compilation, a stub implementation of `acpi_id_table()`
> is added to the Platform adapter; the full implementation will be provided
> in a subsequent patch.
> ---
>  rust/bindings/bindings_helper.h |  1 +
>  rust/kernel/driver.rs           | 58 ++++++++++++++++++++++++++++++---
>  rust/kernel/platform.rs         |  5 +++
>  3 files changed, 60 insertions(+), 4 deletions(-)
> 
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index e0bcd130b494..d974fc6c141f 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -6,6 +6,7 @@
>   * Sorted alphabetically.
>   */
>  
> +#include <linux/acpi.h>
>  #include <kunit/test.h>
>  #include <linux/blk-mq.h>
>  #include <linux/blk_types.h>
> diff --git a/rust/kernel/driver.rs b/rust/kernel/driver.rs
> index ec9166cedfa7..d4098596188a 100644
> --- a/rust/kernel/driver.rs
> +++ b/rust/kernel/driver.rs
> @@ -6,7 +6,7 @@
>  //! register using the [`Registration`] class.
>  
>  use crate::error::{Error, Result};
> -use crate::{device, of, str::CStr, try_pin_init, types::Opaque, ThisModule};
> +use crate::{device, of, acpi, str::CStr, try_pin_init, types::Opaque, ThisModule};
>  use core::pin::Pin;
>  use pin_init::{pin_data, pinned_drop, PinInit};
>  
> @@ -141,6 +141,38 @@ pub trait Adapter {
>      /// The type holding driver private data about each device id supported by the driver.
>      type IdInfo: 'static;
>  
> +    /// The [`acpi::IdTable`] of the corresponding driver
> +    fn acpi_id_table() -> Option<acpi::IdTable<Self::IdInfo>>;
> +
> +    /// 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`].
> +    #[cfg(CONFIG_ACPI)]
> +    fn acpi_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
> +        let table = Self::acpi_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::acpi_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::<acpi::DeviceId>() };
> +
> +            Some(table.info(<acpi::DeviceId as crate::device_id::RawDeviceId>::index(id)))
> +        }
> +    }
> +
> +    #[cfg(not(CONFIG_ACPI))]
> +    #[allow(missing_docs)]
> +    fn acpi_id_info(_dev: &device::Device) -> Option<&'static Self::IdInfo> {
> +        None
> +    }
> +
>      /// The [`of::IdTable`] of the corresponding driver.
>      fn of_id_table() -> Option<of::IdTable<Self::IdInfo>>;
>  
> @@ -178,9 +210,27 @@ 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> {
> -        let id = Self::of_id_info(dev);
> -        if id.is_some() {
> -            return id;
> +        // SAFETY: `id_info` is called from `Adapter::probe_callback` with a valid `dev` argument.
> +        let fwnode = unsafe{ (*dev.as_raw()).fwnode};

There is an abstraction for FwNode on the list [1] that I plan to merge soon.
Generally, it would make sense to build on top of that.

However, I don't understand why we need this and the subsequent
is_acpi_device_node() and is_of_node() checks.

Instead, I think we can keep the existing code and just add the following.

	let id = Self::acpi_id_info(dev);
	if id.is_some() {
	   return id;
	}

[1] https://lore.kernel.org/lkml/20250530192856.1177011-1-remo@buenzli.dev/

> +
> +        // SAFETY: `bindings::is_acpi_device_node` checks `fwnode` before accessing `fwnode->ops`,
> +        // and only compares it with the address of `acpi_device_fwnode_ops`.
> +        if unsafe { bindings::is_acpi_device_node(fwnode) } {

As mentioned above, I think we don't need this check.

> +            let id = Self::acpi_id_info(dev);
> +
> +            if id.is_some() {
> +                return id;
> +            }
> +        }
> +
> +        // SAFETY: `bindings::is_of_node` checks `fwnode` before accessing `fwnode->ops`,
> +        // and only compares it with the address of `of_fwnode_ops`.
> +        if unsafe { bindings::is_of_node(fwnode) } {

Same here.

> +            let id = Self::of_id_info(dev);
> +
> +            if id.is_some() {
> +                return id;
> +            }
>          }
>  
>          None
> diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
> index fd4a494f30e8..3cc9fe6ccfcf 100644
> --- a/rust/kernel/platform.rs
> +++ b/rust/kernel/platform.rs
> @@ -5,6 +5,7 @@
>  //! C header: [`include/linux/platform_device.h`](srctree/include/linux/platform_device.h)
>  
>  use crate::{
> +    acpi,
>      bindings, device, driver,
>      error::{to_result, Result},
>      of,
> @@ -95,6 +96,10 @@ impl<T: Driver + 'static> driver::Adapter for Adapter<T> {
>      fn of_id_table() -> Option<of::IdTable<Self::IdInfo>> {
>          T::OF_ID_TABLE
>      }
> +
> +    fn acpi_id_table() -> Option<acpi::IdTable<Self::IdInfo>> {
> +        None
> +    }
>  }
>  
>  /// Declares a kernel module that exposes a single platform driver.
> -- 
> 2.43.0
>