Message-ID: <20250913161222.3889-3-sergeantsagara@protonmail.com>
Date: Sat, 13 Sep 2025 16:13:06 +0000
From: Rahul Rameshbabu <sergeantsagara@...tonmail.com>
To: linux-input@...r.kernel.org, linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org
Cc: Jiri Kosina <jikos@...nel.org>, a.hindborg@...nel.org, alex.gaynor@...il.com, aliceryhl@...gle.com, benno.lossin@...ton.me, Benjamin Tissoires <benjamin.tissoires@...hat.com>, bjorn3_gh@...tonmail.com, boqun.feng@...il.com, dakr@...nel.org, db48x@...8x.net, gary@...yguo.net, ojeda@...nel.org, tmgross@...ch.edu, peter.hutterer@...-t.net, Rahul Rameshbabu <sergeantsagara@...tonmail.com>
Subject: [PATCH v3 RESEND RESEND 2/3] rust: core abstractions for HID drivers

These abstractions enable the development of HID drivers in Rust by binding
with the HID core C API. They provide Rust types that map to the
equivalents in C. In this initial draft, only hid_device and hid_device_id
are provided direct Rust type equivalents. hid_driver is specially wrapped
with a custom Driver type. The module_hid_driver! macro provides analogous
functionality to its C equivalent. Only the .report_fixup callback is
binded to Rust so far.

Future work for these abstractions would include more bindings for common
HID-related types, such as hid_field, hid_report_enum, and hid_report as
well as more bus callbacks. Providing Rust equivalents to useful core HID
functions will also be necessary for HID driver development in Rust.

Signed-off-by: Rahul Rameshbabu <sergeantsagara@...tonmail.com>
---

Notes:
    Some points I did not address from the last review cycle:
    
        * I did not look into autogenerating all the getter functions for various
          fields exported from the binded C structures.
          - I would be interested in hearing opinions from folks actively involved
            with Rust for Linux on this topic.
    
    Changelog:
    
        v2->v3:
          * Implemented AlwaysRefCounted trait using embedded struct device's
            reference counts instead of the separate reference counter in struct
            hid_device
          * Used &raw mut as appropriate
          * Binded include/linux/device.h for get_device and put_device
          * Cleaned up various comment related formatting
          * Minified dev_err! format string
          * Updated Group enum to be repr(u16)
          * Implemented From<u16> trait for Group
          * Added TODO comment when const_trait_impl stabilizes
          * Made group getter functions return a Group variant instead of a raw
            number
          * Made sure example code builds
        v1->v2:
          * Binded drivers/hid/hid-ids.h for use in Rust drivers
          * Remove pre-emptive referencing of a C HID driver instance before
            it is fully initialized in the driver registration path
          * Moved static getters to generic Device trait implementation, so
            they can be used by all device::DeviceContext
          * Use core macros for supporting DeviceContext transitions
          * Implemented the AlwaysRefCounted and AsRef traits
          * Make use for dev_err! as appropriate
        RFC->v1:
          * Use Danilo's core infrastructure
          * Account for HID device groups
          * Remove probe and remove callbacks
          * Implement report_fixup support
          * Properly comment code including SAFETY comments

 MAINTAINERS                     |   9 +
 drivers/hid/Kconfig             |   8 +
 rust/bindings/bindings_helper.h |   3 +
 rust/kernel/hid.rs              | 503 ++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs              |   2 +
 5 files changed, 525 insertions(+)
 create mode 100644 rust/kernel/hid.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index dd810da5261b..6c60765f2aaa 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10686,6 +10686,15 @@ F:	include/uapi/linux/hid*
 F:	samples/hid/
 F:	tools/testing/selftests/hid/
 
+HID CORE LAYER [RUST]
+M:	Rahul Rameshbabu <sergeantsagara@...tonmail.com>
+R:	Benjamin Tissoires <bentiss@...nel.org>
+L:	linux-input@...r.kernel.org
+S:	Maintained
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/hid/hid.git rust
+F:	drivers/hid/*.rs
+F:	rust/kernel/hid.rs
+
 HID LOGITECH DRIVERS
 R:	Filipe Laíns <lains@...eup.net>
 L:	linux-input@...r.kernel.org
diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 43859fc75747..922e76e18af2 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -744,6 +744,14 @@ config HID_MEGAWORLD_FF
 	Say Y here if you have a Mega World based game controller and want
 	to have force feedback support for it.
 
+config RUST_HID_ABSTRACTIONS
+	bool "Rust HID abstractions support"
+	depends on RUST
+	depends on HID=y
+	help
+	  Adds support needed for HID drivers written in Rust. It provides a
+	  wrapper around the C hid core.
+
 config HID_REDRAGON
 	tristate "Redragon keyboards"
 	default !EXPERT
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 8cbb660e2ec2..7145fb1cdff1 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -45,6 +45,7 @@
 #include <linux/cpufreq.h>
 #include <linux/cpumask.h>
 #include <linux/cred.h>
+#include <linux/device.h>
 #include <linux/device/faux.h>
 #include <linux/dma-mapping.h>
 #include <linux/errname.h>
@@ -52,6 +53,8 @@
 #include <linux/file.h>
 #include <linux/firmware.h>
 #include <linux/fs.h>
+#include <linux/hid.h>
+#include "../../drivers/hid/hid-ids.h"
 #include <linux/jiffies.h>
 #include <linux/jump_label.h>
 #include <linux/mdio.h>
diff --git a/rust/kernel/hid.rs b/rust/kernel/hid.rs
new file mode 100644
index 000000000000..a93804af8b78
--- /dev/null
+++ b/rust/kernel/hid.rs
@@ -0,0 +1,503 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2025 Rahul Rameshbabu <sergeantsagara@...tonmail.com>
+
+//! Abstractions for the HID interface.
+//!
+//! C header: [`include/linux/hid.h`](srctree/include/linux/hid.h)
+
+use crate::{device, device_id::RawDeviceId, driver, error::*, prelude::*, types::Opaque};
+use core::{
+    marker::PhantomData,
+    ptr::{addr_of_mut, NonNull},
+};
+
+/// Indicates the item is static read-only.
+///
+/// Refer to [Device Class Definition for HID 1.11]
+/// Section 6.2.2.5 Input, Output, and Feature Items.
+///
+/// [Device Class Definition for HID 1.11]: https://www.usb.org/sites/default/files/hid1_11.pdf
+pub const MAIN_ITEM_CONSTANT: u8 = bindings::HID_MAIN_ITEM_CONSTANT as u8;
+
+/// Indicates the item represents data from a physical control.
+///
+/// Refer to [Device Class Definition for HID 1.11]
+/// Section 6.2.2.5 Input, Output, and Feature Items.
+///
+/// [Device Class Definition for HID 1.11]: https://www.usb.org/sites/default/files/hid1_11.pdf
+pub const MAIN_ITEM_VARIABLE: u8 = bindings::HID_MAIN_ITEM_VARIABLE as u8;
+
+/// Indicates the item should be treated as a relative change from the previous
+/// report.
+///
+/// Refer to [Device Class Definition for HID 1.11]
+/// Section 6.2.2.5 Input, Output, and Feature Items.
+///
+/// [Device Class Definition for HID 1.11]: https://www.usb.org/sites/default/files/hid1_11.pdf
+pub const MAIN_ITEM_RELATIVE: u8 = bindings::HID_MAIN_ITEM_RELATIVE as u8;
+
+/// Indicates the item should wrap around when reaching the extreme high or
+/// extreme low values.
+///
+/// Refer to [Device Class Definition for HID 1.11]
+/// Section 6.2.2.5 Input, Output, and Feature Items.
+///
+/// [Device Class Definition for HID 1.11]: https://www.usb.org/sites/default/files/hid1_11.pdf
+pub const MAIN_ITEM_WRAP: u8 = bindings::HID_MAIN_ITEM_WRAP as u8;
+
+/// Indicates the item should wrap around when reaching the extreme high or
+/// extreme low values.
+///
+/// Refer to [Device Class Definition for HID 1.11]
+/// Section 6.2.2.5 Input, Output, and Feature Items.
+///
+/// [Device Class Definition for HID 1.11]: https://www.usb.org/sites/default/files/hid1_11.pdf
+pub const MAIN_ITEM_NONLINEAR: u8 = bindings::HID_MAIN_ITEM_NONLINEAR as u8;
+
+/// Indicates whether the control has a preferred state it will physically
+/// return to without user intervention.
+///
+/// Refer to [Device Class Definition for HID 1.11]
+/// Section 6.2.2.5 Input, Output, and Feature Items.
+///
+/// [Device Class Definition for HID 1.11]: https://www.usb.org/sites/default/files/hid1_11.pdf
+pub const MAIN_ITEM_NO_PREFERRED: u8 = bindings::HID_MAIN_ITEM_NO_PREFERRED as u8;
+
+/// Indicates whether the control has a physical state where it will not send
+/// any reports.
+///
+/// Refer to [Device Class Definition for HID 1.11]
+/// Section 6.2.2.5 Input, Output, and Feature Items.
+///
+/// [Device Class Definition for HID 1.11]: https://www.usb.org/sites/default/files/hid1_11.pdf
+pub const MAIN_ITEM_NULL_STATE: u8 = bindings::HID_MAIN_ITEM_NULL_STATE as u8;
+
+/// Indicates whether the control requires host system logic to change state.
+///
+/// Refer to [Device Class Definition for HID 1.11]
+/// Section 6.2.2.5 Input, Output, and Feature Items.
+///
+/// [Device Class Definition for HID 1.11]: https://www.usb.org/sites/default/files/hid1_11.pdf
+pub const MAIN_ITEM_VOLATILE: u8 = bindings::HID_MAIN_ITEM_VOLATILE as u8;
+
+/// Indicates whether the item is fixed size or a variable buffer of bytes.
+///
+/// Refer to [Device Class Definition for HID 1.11]
+/// Section 6.2.2.5 Input, Output, and Feature Items.
+///
+/// [Device Class Definition for HID 1.11]: https://www.usb.org/sites/default/files/hid1_11.pdf
+pub const MAIN_ITEM_BUFFERED_BYTE: u8 = bindings::HID_MAIN_ITEM_BUFFERED_BYTE as u8;
+
+/// HID device groups are intended to help categories HID devices based on a set
+/// of common quirks and logic that they will require to function correctly.
+#[repr(u16)]
+pub enum Group {
+    /// Used to match a device against any group when probing.
+    Any = bindings::HID_GROUP_ANY as u16,
+
+    /// Indicates a generic device that should need no custom logic from the
+    /// core HID stack.
+    Generic = bindings::HID_GROUP_GENERIC as u16,
+
+    /// Maps multitouch devices to hid-multitouch instead of hid-generic.
+    Multitouch = bindings::HID_GROUP_MULTITOUCH as u16,
+
+    /// Used for autodetecing and mapping of HID sensor hubs to
+    /// hid-sensor-hub.
+    SensorHub = bindings::HID_GROUP_SENSOR_HUB as u16,
+
+    /// Used for autodetecing and mapping Win 8 multitouch devices to set the
+    /// needed quirks.
+    MultitouchWin8 = bindings::HID_GROUP_MULTITOUCH_WIN_8 as u16,
+
+    // Vendor-specific device groups.
+    /// Used to distinguish Synpatics touchscreens from other products. The
+    /// touchscreens will be handled by hid-multitouch instead, while everything
+    /// else will be managed by hid-rmi.
+    RMI = bindings::HID_GROUP_RMI as u16,
+
+    /// Used for hid-core handling to automatically identify Wacom devices and
+    /// have them probed by hid-wacom.
+    Wacom = bindings::HID_GROUP_WACOM as u16,
+
+    /// Used by logitech-djreceiver and logitech-djdevice to autodetect if
+    /// devices paied to the DJ receivers are DJ devices and handle them with
+    /// the device driver.
+    LogitechDJDevice = bindings::HID_GROUP_LOGITECH_DJ_DEVICE as u16,
+
+    /// Since the Valve Steam Controller only has vendor-specific usages,
+    /// prevent hid-generic from parsing its reports since there would be
+    /// nothing hid-generic could do for the device.
+    Steam = bindings::HID_GROUP_STEAM as u16,
+
+    /// Used to differentiate 27 Mhz frequency Logitech DJ devices from other
+    /// Logitech DJ devices.
+    Logitech27MHzDevice = bindings::HID_GROUP_LOGITECH_27MHZ_DEVICE as u16,
+
+    /// Used for autodetecting and mapping Vivaldi devices to hid-vivaldi.
+    Vivaldi = bindings::HID_GROUP_VIVALDI as u16,
+}
+
+// TODO: use `const_trait_impl` once stabilized:
+//
+// ```
+// impl const From<Group> for u16 {
+//     /// [`Group`] variants are represented by [`u16`] values.
+//     fn from(value: Group) -> Self {
+//         value as Self
+//     }
+// }
+// ```
+impl Group {
+    /// Internal function used to convert [`Group`] variants into [`u16`].
+    const fn into(self) -> u16 {
+        self as u16
+    }
+}
+
+impl From<u16> for Group {
+    /// [`u16`] values can be safely converted to [`Group`] variants.
+    fn from(value: u16) -> Self {
+        match value.into() {
+            bindings::HID_GROUP_GENERIC => Group::Generic,
+            bindings::HID_GROUP_MULTITOUCH => Group::Multitouch,
+            bindings::HID_GROUP_SENSOR_HUB => Group::SensorHub,
+            bindings::HID_GROUP_MULTITOUCH_WIN_8 => Group::MultitouchWin8,
+            bindings::HID_GROUP_RMI => Group::RMI,
+            bindings::HID_GROUP_WACOM => Group::Wacom,
+            bindings::HID_GROUP_LOGITECH_DJ_DEVICE => Group::LogitechDJDevice,
+            bindings::HID_GROUP_STEAM => Group::Steam,
+            bindings::HID_GROUP_LOGITECH_27MHZ_DEVICE => Group::Logitech27MHzDevice,
+            bindings::HID_GROUP_VIVALDI => Group::Vivaldi,
+            _ => Group::Any,
+        }
+    }
+}
+
+/// The HID device representation.
+///
+/// This structure represents the Rust abstraction for a C `struct hid_device`.
+/// The implementation abstracts the usage of an already existing C `struct
+/// hid_device` within Rust code that we get passed from the C side.
+///
+/// # Invariants
+///
+/// A [`Device`] instance represents a valid `struct hid_device` created by the
+/// C portion of the kernel.
+#[repr(transparent)]
+pub struct Device<Ctx: device::DeviceContext = device::Normal>(
+    Opaque<bindings::hid_device>,
+    PhantomData<Ctx>,
+);
+
+impl<Ctx: device::DeviceContext> Device<Ctx> {
+    fn as_raw(&self) -> *mut bindings::hid_device {
+        self.0.get()
+    }
+
+    /// Returns the HID transport bus ID.
+    pub fn bus(&self) -> u16 {
+        // SAFETY: `self.as_raw` is a valid pointer to a `struct hid_device`
+        unsafe { *self.as_raw() }.bus
+    }
+
+    /// Returns the HID report group.
+    pub fn group(&self) -> Group {
+        // SAFETY: `self.as_raw` is a valid pointer to a `struct hid_device`
+        unsafe { *self.as_raw() }.group.into()
+    }
+
+    /// Returns the HID vendor ID.
+    pub fn vendor(&self) -> u32 {
+        // SAFETY: `self.as_raw` is a valid pointer to a `struct hid_device`
+        unsafe { *self.as_raw() }.vendor
+    }
+
+    /// Returns the HID product ID.
+    pub fn product(&self) -> u32 {
+        // SAFETY: `self.as_raw` is a valid pointer to a `struct hid_device`
+        unsafe { *self.as_raw() }.product
+    }
+}
+
+// SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
+// argument.
+kernel::impl_device_context_deref!(unsafe { Device });
+kernel::impl_device_context_into_aref!(Device);
+
+// SAFETY: Instances of `Device` are always reference-counted.
+unsafe impl crate::types::AlwaysRefCounted for Device {
+    fn inc_ref(&self) {
+        // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
+        unsafe { bindings::get_device(&raw mut (*self.as_raw()).dev) };
+    }
+
+    unsafe fn dec_ref(obj: NonNull<Self>) {
+        // SAFETY: The safety requirements guarantee that the refcount is non-zero.
+        unsafe { bindings::put_device(&raw mut (*obj.cast::<bindings::hid_device>().as_ptr()).dev) }
+    }
+}
+
+impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
+    fn as_ref(&self) -> &device::Device<Ctx> {
+        // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
+        // `struct hid_device`.
+        let dev = unsafe { addr_of_mut!((*self.as_raw()).dev) };
+
+        // SAFETY: `dev` points to a valid `struct device`.
+        unsafe { device::Device::as_ref(dev) }
+    }
+}
+
+/// Abstraction for the HID device ID structure `struct hid_device_id`.
+#[repr(transparent)]
+#[derive(Clone, Copy)]
+pub struct DeviceId(bindings::hid_device_id);
+
+impl DeviceId {
+    /// Equivalent to C's `HID_USB_DEVICE` macro.
+    ///
+    /// Create a new `hid::DeviceId` from a group, vendor ID, and device ID
+    /// number.
+    pub const fn new_usb(group: Group, vendor: u32, product: u32) -> Self {
+        Self(bindings::hid_device_id {
+            bus: 0x3, // BUS_USB
+            group: group.into(),
+            vendor,
+            product,
+            driver_data: 0,
+        })
+    }
+
+    /// Returns the HID transport bus ID.
+    pub fn bus(&self) -> u16 {
+        self.0.bus
+    }
+
+    /// Returns the HID report group.
+    pub fn group(&self) -> Group {
+        self.0.group.into()
+    }
+
+    /// Returns the HID vendor ID.
+    pub fn vendor(&self) -> u32 {
+        self.0.vendor
+    }
+
+    /// Returns the HID product ID.
+    pub fn product(&self) -> u32 {
+        self.0.product
+    }
+}
+
+// SAFETY:
+// * `DeviceId` is a `#[repr(transparent)` wrapper of `hid_device_id` and does not add
+//   additional invariants, so it's safe to transmute to `RawType`.
+// * `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.
+unsafe impl RawDeviceId for DeviceId {
+    type RawType = bindings::hid_device_id;
+
+    const DRIVER_DATA_OFFSET: usize = core::mem::offset_of!(bindings::hid_device_id, driver_data);
+
+    fn index(&self) -> usize {
+        self.0.driver_data
+    }
+}
+
+/// [`IdTable`] type for HID.
+pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>;
+
+/// Create a HID [`IdTable`] with its alias for modpost.
+#[macro_export]
+macro_rules! hid_device_table {
+    ($table_name:ident, $module_table_name:ident, $id_info_type: ty, $table_data: expr) => {
+        const $table_name: $crate::device_id::IdArray<
+            $crate::hid::DeviceId,
+            $id_info_type,
+            { $table_data.len() },
+        > = $crate::device_id::IdArray::new($table_data);
+
+        $crate::module_device_table!("hid", $module_table_name, $table_name);
+    };
+}
+
+/// The HID driver trait.
+///
+/// # Examples
+///
+/// ```
+/// use kernel::{bindings, device, hid};
+///
+/// struct MyDriver;
+///
+/// kernel::hid_device_table!(
+///     HID_TABLE,
+///     MODULE_HID_TABLE,
+///     <MyDriver as hid::Driver>::IdInfo,
+///     [(
+///         hid::DeviceId::new_usb(
+///             hid::Group::Steam,
+///             bindings::USB_VENDOR_ID_VALVE,
+///             bindings::USB_DEVICE_ID_STEAM_DECK,
+///         ),
+///         (),
+///     )]
+/// );
+///
+/// #[vtable]
+/// impl hid::Driver for MyDriver {
+///     type IdInfo = ();
+///     const ID_TABLE: hid::IdTable<Self::IdInfo> = &HID_TABLE;
+///
+///     /// This function is optional to implement.
+///     fn report_fixup<'a, 'b: 'a>(_hdev: &hid::Device<device::Core>, rdesc: &'b mut [u8]) -> &'a [u8] {
+///         // Perform some report descriptor fixup.
+///         rdesc
+///     }
+/// }
+/// ```
+/// Drivers must implement this trait in order to get a HID driver registered.
+/// Please refer to the `Adapter` documentation for an example.
+#[vtable]
+pub trait Driver: Send {
+    /// The type holding information about each device id supported by the driver.
+    // TODO: Use `associated_type_defaults` once stabilized:
+    //
+    // ```
+    // type IdInfo: 'static = ();
+    // ```
+    type IdInfo: 'static;
+
+    /// The table of device ids supported by the driver.
+    const ID_TABLE: IdTable<Self::IdInfo>;
+
+    /// Called before report descriptor parsing. Can be used to mutate the
+    /// report descriptor before the core HID logic processes the descriptor.
+    /// Useful for problematic report descriptors that prevent HID devices from
+    /// functioning correctly.
+    ///
+    /// Optional to implement.
+    fn report_fixup<'a, 'b: 'a>(_hdev: &Device<device::Core>, _rdesc: &'b mut [u8]) -> &'a [u8] {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+}
+
+/// An adapter for the registration of HID drivers.
+pub struct Adapter<T: Driver>(T);
+
+// SAFETY: A call to `unregister` for a given instance of `RegType` is guaranteed to be valid if
+// a preceding call to `register` has been successful.
+unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
+    type RegType = bindings::hid_driver;
+
+    unsafe fn register(
+        hdrv: &Opaque<Self::RegType>,
+        name: &'static CStr,
+        module: &'static ThisModule,
+    ) -> Result {
+        // SAFETY: It's safe to set the fields of `struct hid_driver` on initialization.
+        unsafe {
+            (*hdrv.get()).name = name.as_char_ptr();
+            (*hdrv.get()).id_table = T::ID_TABLE.as_ptr();
+            (*hdrv.get()).report_fixup = if T::HAS_REPORT_FIXUP {
+                Some(Self::report_fixup_callback)
+            } else {
+                None
+            };
+        }
+
+        // SAFETY: `hdrv` is guaranteed to be a valid `RegType`
+        to_result(unsafe {
+            bindings::__hid_register_driver(hdrv.get(), module.0, name.as_char_ptr())
+        })
+    }
+
+    unsafe fn unregister(hdrv: &Opaque<Self::RegType>) {
+        // SAFETY: `hdrv` is guaranteed to be a valid `RegType`
+        unsafe { bindings::hid_unregister_driver(hdrv.get()) }
+    }
+}
+
+impl<T: Driver + 'static> Adapter<T> {
+    extern "C" fn report_fixup_callback(
+        hdev: *mut bindings::hid_device,
+        buf: *mut u8,
+        size: *mut kernel::ffi::c_uint,
+    ) -> *const u8 {
+        // SAFETY: The HID subsystem only ever calls the report_fixup callback
+        // with a valid pointer to a `struct hid_device`.
+        //
+        // INVARIANT: `hdev` is valid for the duration of
+        // `report_fixup_callback()`.
+        let hdev = unsafe { &*hdev.cast::<Device<device::Core>>() };
+
+        // SAFETY: The HID subsystem only ever calls the report_fixup callback
+        // with a valid pointer to a `kernel::ffi::c_uint`.
+        //
+        // INVARIANT: `size` is valid for the duration of
+        // `report_fixup_callback()`.
+        let buf_len: usize = match unsafe { *size }.try_into() {
+            Ok(len) => len,
+            Err(e) => {
+                dev_err!(
+                    hdev.as_ref(),
+                    "Cannot fix report description due to {}!\n",
+                    e
+                );
+
+                return buf;
+            }
+        };
+
+        // Build a mutable Rust slice from `buf` and `size`.
+        //
+        // SAFETY: The HID subsystem only ever calls the `report_fixup callback`
+        // with a valid pointer to a `u8` buffer.
+        //
+        // INVARIANT: `buf` is valid for the duration of
+        // `report_fixup_callback()`.
+        let rdesc_slice = unsafe { core::slice::from_raw_parts_mut(buf, buf_len) };
+        let rdesc_slice = T::report_fixup(hdev, rdesc_slice);
+
+        match rdesc_slice.len().try_into() {
+            // SAFETY: The HID subsystem only ever calls the report_fixup
+            // callback with a valid pointer to a `kernel::ffi::c_uint`.
+            //
+            // INVARIANT: `size` is valid for the duration of
+            // `report_fixup_callback()`.
+            Ok(len) => unsafe { *size = len },
+            Err(e) => {
+                dev_err!(
+                    hdev.as_ref(),
+                    "Fixed report description will not be used due to {}!\n",
+                    e
+                );
+
+                return buf;
+            }
+        }
+
+        rdesc_slice.as_ptr()
+    }
+}
+
+/// Declares a kernel module that exposes a single HID driver.
+///
+/// # Examples
+///
+/// ```ignore
+/// kernel::module_hid_driver! {
+///     type: MyDriver,
+///     name: "Module name",
+///     authors: ["Author name"],
+///     description: "Description",
+///     license: "GPL",
+/// }
+/// ```
+#[macro_export]
+macro_rules! module_hid_driver {
+    ($($f:tt)*) => {
+        $crate::module_driver!(<T>, $crate::hid::Adapter<T>, { $($f)* });
+    };
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index e88bc4b27d6e..44c107f20174 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -80,6 +80,8 @@
 pub mod firmware;
 pub mod fmt;
 pub mod fs;
+#[cfg(CONFIG_RUST_HID_ABSTRACTIONS)]
+pub mod hid;
 pub mod init;
 pub mod io;
 pub mod ioctl;
-- 
2.47.2

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