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Wysocki" Cc: linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, Matthew Maurer Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable 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 --- MAINTAINERS | 1 + rust/bindings/bindings_helper.h | 1 + rust/kernel/lib.rs | 2 + rust/kernel/soc.rs | 145 ++++++++++++++++++++++++++++++++++++= ++++ 4 files changed, 149 insertions(+) diff --git a/MAINTAINERS b/MAINTAINERS index c5a7cda26c600e49c7ab0d547306d3281333f672..4ff01fb0f1bda27002094113c0b= f9d074d28fdb6 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_helpe= r.h index a067038b4b422b4256f4a2b75fe644d47e6e82c8..9fdf76ca630e00715503e2a3a80= 9bedc895697fd 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -80,6 +80,7 @@ #include #include #include +#include #include #include #include diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index f812cf12004286962985a068665443dc22c389a2..6d637e2fed1b605e2dfc2e7b224= 7179439a90ba9 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..fb9e461218787b5546805c0f04f= adbc5e3e054a6 --- /dev/null +++ b/rust/kernel/soc.rs @@ -0,0 +1,145 @@ +// 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 provi= ded to other drivers to +/// match against via `soc_device_match` (not yet available in Rust) to en= able quirks or +/// device-specific support where necessary. +/// +/// All fields are freeform - they have no specific formatting, just defin= ed meanings. +/// For example, the [`machine`](`Attributes::machine`) field could be "DB= 8500" or +/// "Qualcomm Technologies, Inc. SM8560 HDK", but regardless it should ide= ntify 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. SM856= 0 HDK". + /// + /// If this field is not populated, the SoC infrastructure will try to= populate it from + /// `/model` in the device tree. + pub machine: Option, + /// The broader class this SoC belongs to. Examples include ux500 + /// (for DB8500) or Snapdragon (for SM8650). + /// + /// On chips with ARM firmware supporting SMCCC v1.2+, this may be a J= EDEC JEP106 manufacturer + /// identification. + pub family: Option, + /// The manufacturing revision of the part. Frequently this is MAJOR.M= INOR, but not always. + pub revision: Option, + /// Serial Number - uniquely identifies a specific SoC. If present, sh= ould be unique (buying a + /// replacement part should change it if present). This field cannot b= e matched on and is + /// solely present to export through /sys. + pub serial_number: Option, + /// SoC ID - identifies a specific SoC kind in question, sometimes mor= e specifically than + /// `machine` if the same SoC is used in multiple products. Some devic= es 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 J= EDEC JEP106 manufacturer + /// identification (the family value) followed by a colon and then a 4= -digit ID value. + pub soc_id: Option, +} + +struct BuiltAttributes { + // While `inner` has pointers to `_backing`, it is to the interior of = the `CStrings`, not + // `backing` itself, so it does not need to be pinned. + _backing: Attributes, + // `Opaque` makes us `!Unpin`, as the registration holds a pointer to = `inner` when used. + inner: Opaque, +} + +fn cstring_to_c(mcs: &Option) -> *const kernel::ffi::c_char { + mcs.as_ref() + .map(|cs| cs.as_char_ptr()) + .unwrap_or(core::ptr::null()) +} + +impl BuiltAttributes { + fn as_mut_ptr(&self) -> *mut bindings::soc_device_attribute { + self.inner.get() + } +} + +impl Attributes { + fn build(self) -> BuiltAttributes { + BuiltAttributes { + inner: Opaque::new(bindings::soc_device_attribute { + machine: cstring_to_c(&self.machine), + family: cstring_to_c(&self.family), + revision: cstring_to_c(&self.revision), + serial_number: cstring_to_c(&self.serial_number), + soc_id: cstring_to_c(&self.soc_id), + data: core::ptr::null(), + custom_attr_group: core::ptr::null(), + }), + _backing: self, + } + } +} + +/// # Safety +/// If a device is returned (e.g. no error), `attr` must remain valid for = reads until the +/// returned pointer is released through `soc_device_unregister`. +unsafe fn register_device(attr: Pin<&BuiltAttributes>) -> Result> { + let raw_soc =3D + // SAFETY: + // * The struct provided through attr is backed by pinned data= next to it, so as + // long as attr lives, the strings pointed to by the struct = will too. + // * `attr` is pinned, so the pinned data won't move. + // * If it returns a device, and so others may try to read thi= s data, by caller + // invariant, `attr` won't be released until the device is. + error::from_err_ptr(unsafe { bindings::soc_device_register(att= r.as_mut_ptr()) })?; + // `soc_device_register` should not return NULL, but it doesn't hurt t= o be paranoid. + NonNull::new(raw_soc).ok_or(EINVAL) +} + +#[pin_data(PinnedDrop)] +/// Registration handle for your soc_dev. If you let it go out of scope, y= our soc_dev will be +/// unregistered. +pub struct Registration { + #[pin] + attr: BuiltAttributes, + soc_dev: NonNull, +} + +// SAFETY: We provide no operations through `&Registration`. +unsafe impl Sync for Registration {} + +// SAFETY: All pointers are normal allocations, not thread-specific. +unsafe impl Send for Registration {} + +#[pinned_drop] +impl PinnedDrop for Registration { + fn drop(self: Pin<&mut Self>) { + // SAFETY: Device always contains a live pointer to a soc_device t= hat can be unregistered + unsafe { bindings::soc_device_unregister(self.soc_dev.as_ptr()) } + } +} + +impl Registration { + /// Register a new SoC device + pub fn register(attr: Attributes) -> impl PinInit { + try_pin_init!(&this in Self { + attr: attr.build(), + // SAFETY: We have already initialized attr, and we ar= e inside PinInit and Self + // is !Unpin, so attr won't be moved and is valid. If = it returns success, attr + // will not be dropped until after our `PinnedDrop` im= plementation runs, so the + // device will be unregistered first. + soc_dev: unsafe { + register_device(Pin::new_unchecked(&(*this.as_ptr(= )).attr))? + }, + }? Error) + } +} --=20 2.52.0.305.g3fc767764a-goog