Re: [PATCH v3 1/3] rust: Add soc_device support

["Alexandre Courbot" <acourbot@nvidia.com>]

On Wed Dec 17, 2025 at 4:24 AM JST, Matthew Maurer wrote:
> Allow SoC drivers in Rust to present metadata about their devices to
> userspace through /sys/devices/socX and other drivers to identify their
> properties through `soc_device_match`.
>
> Signed-off-by: Matthew Maurer <mmaurer@google.com>
> ---
>  MAINTAINERS                     |   1 +
>  rust/bindings/bindings_helper.h |   1 +
>  rust/kernel/lib.rs              |   2 +
>  rust/kernel/soc.rs              | 135 ++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 139 insertions(+)
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index c5a7cda26c600e49c7ab0d547306d3281333f672..4ff01fb0f1bda27002094113c0bf9d074d28fdb6 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -7700,6 +7700,7 @@ F:	rust/kernel/devres.rs
>  F:	rust/kernel/driver.rs
>  F:	rust/kernel/faux.rs
>  F:	rust/kernel/platform.rs
> +F:	rust/kernel/soc.rs
>  F:	samples/rust/rust_debugfs.rs
>  F:	samples/rust/rust_debugfs_scoped.rs
>  F:	samples/rust/rust_driver_platform.rs
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index a067038b4b422b4256f4a2b75fe644d47e6e82c8..9fdf76ca630e00715503e2a3a809bedc895697fd 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -80,6 +80,7 @@
>  #include <linux/sched.h>
>  #include <linux/security.h>
>  #include <linux/slab.h>
> +#include <linux/sys_soc.h>
>  #include <linux/task_work.h>
>  #include <linux/tracepoint.h>
>  #include <linux/usb.h>
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index f812cf12004286962985a068665443dc22c389a2..6d637e2fed1b605e2dfc2e7b2247179439a90ba9 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -138,6 +138,8 @@
>  pub mod seq_file;
>  pub mod sizes;
>  pub mod slice;
> +#[cfg(CONFIG_SOC_BUS)]
> +pub mod soc;
>  mod static_assert;
>  #[doc(hidden)]
>  pub mod std_vendor;
> diff --git a/rust/kernel/soc.rs b/rust/kernel/soc.rs
> new file mode 100644
> index 0000000000000000000000000000000000000000..0d6a36c83cb67ef20dc1e3d3995752f36e25ac9f
> --- /dev/null
> +++ b/rust/kernel/soc.rs
> @@ -0,0 +1,135 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +// Copyright (C) 2025 Google LLC.
> +
> +//! SoC Driver Abstraction.
> +//!
> +//! C header: [`include/linux/sys_soc.h`](srctree/include/linux/sys_soc.h)
> +
> +use crate::{
> +    bindings,
> +    error,
> +    prelude::*,
> +    str::CString,
> +    types::Opaque, //
> +};
> +use core::ptr::NonNull;
> +
> +/// Attributes for a SoC device.
> +///
> +/// These are both exported to userspace under /sys/devices/socX and provided to other drivers to
> +/// match against via `soc_device_match` (not yet available in Rust) to enable quirks or
> +/// device-specific support where necessary.
> +///
> +/// All fields are freeform - they have no specific formatting, just defined meanings.
> +/// For example, the [`machine`](`Attributes::machine`) field could be "DB8500" or
> +/// "Qualcomm Technologies, Inc. SM8560 HDK", but regardless it should identify a board or product.
> +pub struct Attributes {
> +    /// Should generally be a board ID or product ID. Examples
> +    /// include DB8500 (ST-Ericsson) or "Qualcomm Technologies, inc. SM8560 HDK".
> +    ///
> +    /// If this field is not populated, the SoC infrastructure will try to populate it from
> +    /// `/model` in the device tree.
> +    pub machine: Option<CString>,
> +    /// The broader class this SoC belongs to. Examples include ux500
> +    /// (for DB8500) or Snapdragon (for SM8650).

Formatting of the comments seems a bit off (also appears in other
places, please reapply formatting globally to be sure).

> +    ///
> +    /// On chips with ARM firmware supporting SMCCC v1.2+, this may be a JEDEC JEP106 manufacturer
> +    /// identification.
> +    pub family: Option<CString>,
> +    /// The manufacturing revision of the part. Frequently this is MAJOR.MINOR, but not always.
> +    pub revision: Option<CString>,
> +    /// Serial Number - uniquely identifies a specific SoC. If present, should be unique (buying a
> +    /// replacement part should change it if present). This field cannot be matched on and is
> +    /// solely present to export through /sys.
> +    pub serial_number: Option<CString>,
> +    /// SoC ID - identifies a specific SoC kind in question, sometimes more specifically than
> +    /// `machine` if the same SoC is used in multiple products. Some devices use this to specify a
> +    /// SoC name, e.g. "I.MX??", and others just print an ID number (e.g. Tegra and Qualcomm).
> +    ///
> +    /// On chips with ARM firmware supporting SMCCC v1.2+, this may be a JEDEC JEP106 manufacturer
> +    /// identification (the family value) followed by a colon and then a 4-digit ID value.
> +    pub soc_id: Option<CString>,
> +}
> +
> +struct BuiltAttributes {

Even though this struct is private, some short documentation would be
helpful - actually the explanation about the relationship between
`_backing` and `inner` belongs here imho instead of in the member's
documentation.