Re: [PATCH v6 1/2] rust: core abstractions for HID drivers

From: Rahul Rameshbabu

Date: Sun Feb 22 2026 - 21:49:05 EST

On Sun, 22 Feb, 2026 15:39:45 -0800 "Terry Junge" <linuxhid@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> On 2/22/26 1:56 PM, Rahul Rameshbabu wrote:
>> 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@xxxxxxxxxxxxxx>
>> ---
>>
>> Notes:
>> Changelog:
>>
>> v5->v6:
>> * Converted From<u16> for Group to TryFrom<u16> to properly handle
>> error case
>> * Renamed into method for Group to into_u16 to not conflate with the
>> From trait
>> * Refactored new upstream changes to RegistrationOps
>> * Implemented DriverLayout trait for hid::Adapter<T>
>> v4->v5:
>> * Add rust/ to drivers/hid/Makefile
>> * Implement RawDeviceIdIndex trait
>> v3->v4:
>> * Removed specifying tree in MAINTAINERS file since that is up for
>> debate
>> * Minor rebase cleanup
>> * Moved driver logic under drivers/hid/rust
>> 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 | 8 +
>> drivers/hid/Kconfig | 2 +
>> drivers/hid/Makefile | 2 +
>> drivers/hid/rust/Kconfig | 12 +
>> rust/bindings/bindings_helper.h | 3 +
>> rust/kernel/hid.rs | 530 ++++++++++++++++++++++++++++++++
>> rust/kernel/lib.rs | 2 +
>> 7 files changed, 559 insertions(+)
>> create mode 100644 drivers/hid/rust/Kconfig
>> create mode 100644 rust/kernel/hid.rs
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index b8d8a5c41597..1fee14024fa2 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -11319,6 +11319,14 @@ F: include/uapi/linux/hid*
>> F: samples/hid/
>> F: tools/testing/selftests/hid/
>>
>> +HID CORE LAYER [RUST]
>> +M: Rahul Rameshbabu <sergeantsagara@xxxxxxxxxxxxxx>
>> +R: Benjamin Tissoires <bentiss@xxxxxxxxxx>
>> +L: linux-input@xxxxxxxxxxxxxxx
>> +S: Maintained
>> +F: drivers/hid/rust/*.rs
>> +F: rust/kernel/hid.rs
>> +
>> HID LOGITECH DRIVERS
>> R: Filipe Laíns <lains@xxxxxxxxxx>
>> L: linux-input@xxxxxxxxxxxxxxx
>> diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
>> index c1d9f7c6a5f2..750c2d49a806 100644
>> --- a/drivers/hid/Kconfig
>> +++ b/drivers/hid/Kconfig
>> @@ -1439,6 +1439,8 @@ endmenu
>>
>> source "drivers/hid/bpf/Kconfig"
>>
>> +source "drivers/hid/rust/Kconfig"
>> +
>> source "drivers/hid/i2c-hid/Kconfig"
>>
>> source "drivers/hid/intel-ish-hid/Kconfig"
>> diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
>> index e01838239ae6..b78ab84c47b4 100644
>> --- a/drivers/hid/Makefile
>> +++ b/drivers/hid/Makefile
>> @@ -8,6 +8,8 @@ hid-$(CONFIG_HID_HAPTIC) += hid-haptic.o
>>
>> obj-$(CONFIG_HID_BPF) += bpf/
>>
>> +obj-$(CONFIG_RUST_HID_ABSTRACTIONS) += rust/
>> +
>> obj-$(CONFIG_HID) += hid.o
>> obj-$(CONFIG_UHID) += uhid.o
>>
>> diff --git a/drivers/hid/rust/Kconfig b/drivers/hid/rust/Kconfig
>> new file mode 100644
>> index 000000000000..d3247651829e
>> --- /dev/null
>> +++ b/drivers/hid/rust/Kconfig
>> @@ -0,0 +1,12 @@
>> +# SPDX-License-Identifier: GPL-2.0-only
>> +menu "Rust HID support"
>> +
>> +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.
>> +
>> +endmenu # Rust HID support
>> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
>> index 083cc44aa952..200e58af27a3 100644
>> --- a/rust/bindings/bindings_helper.h
>> +++ b/rust/bindings/bindings_helper.h
>> @@ -48,6 +48,7 @@
>> #include <linux/cpumask.h>
>> #include <linux/cred.h>
>> #include <linux/debugfs.h>
>> +#include <linux/device.h>
>> #include <linux/device/faux.h>
>> #include <linux/dma-direction.h>
>> #include <linux/dma-mapping.h>
>> @@ -60,6 +61,8 @@
>> #include <linux/i2c.h>
>> #include <linux/interrupt.h>
>> #include <linux/io-pgtable.h>
>> +#include <linux/hid.h>
>> +#include "../../drivers/hid/hid-ids.h"
>> #include <linux/ioport.h>
>> #include <linux/jiffies.h>
>> #include <linux/jump_label.h>
>> diff --git a/rust/kernel/hid.rs b/rust/kernel/hid.rs
>> new file mode 100644
>> index 000000000000..b9db542d923a
>> --- /dev/null
>> +++ b/rust/kernel/hid.rs
>> @@ -0,0 +1,530 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +
>> +// Copyright (C) 2025 Rahul Rameshbabu <sergeantsagara@xxxxxxxxxxxxxx>
>> +
>> +//! Abstractions for the HID interface.
>> +//!
>> +//! C header: [`include/linux/hid.h`](srctree/include/linux/hid.h)
>> +
>> +use crate::{
>> + device,
>> + device_id::{
>> + RawDeviceId,
>> + RawDeviceIdIndex, //
>> + },
>> + 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_MAIN_ITEM_BUFFERED_BYTE has a value of 0x100 which will not fit in a u8.
> Maybe all the MAIN_ITEM_* bits should bound as u16?
>
> HID 1.11 actually defines them as a u32 with bits 9-31 reserved for future use.

Thanks Terry for pointing this out. I will give some time for other
reviewers to comment but will make the needed change for a v7.

Thanks,
Rahul Rameshbabu

>
> Thanks
> Terry
>
> +
>> +/// 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_u16(self) -> u16 {
>> + self as u16
>> + }
>> +}
>> +
>> +impl TryFrom<u16> for Group {
>> + type Error = &'static str;
>> +
>> + /// [`u16`] values can be safely converted to [`Group`] variants.
>> + fn try_from(value: u16) -> Result<Group, Self::Error> {
>> + match value.into() {
>> + bindings::HID_GROUP_GENERIC => Ok(Group::Generic),
>> + bindings::HID_GROUP_MULTITOUCH => Ok(Group::Multitouch),
>> + bindings::HID_GROUP_SENSOR_HUB => Ok(Group::SensorHub),
>> + bindings::HID_GROUP_MULTITOUCH_WIN_8 => Ok(Group::MultitouchWin8),
>> + bindings::HID_GROUP_RMI => Ok(Group::RMI),
>> + bindings::HID_GROUP_WACOM => Ok(Group::Wacom),
>> + bindings::HID_GROUP_LOGITECH_DJ_DEVICE => Ok(Group::LogitechDJDevice),
>> + bindings::HID_GROUP_STEAM => Ok(Group::Steam),
>> + bindings::HID_GROUP_LOGITECH_27MHZ_DEVICE => Ok(Group::Logitech27MHzDevice),
>> + bindings::HID_GROUP_VIVALDI => Ok(Group::Vivaldi),
>> + _ => Err("Unknown HID group encountered!"),
>> + }
>> + }
>> +}
>> +
>> +/// 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) -> Result<Group, &'static str> {
>> + // SAFETY: `self.as_raw` is a valid pointer to a `struct hid_device`
>> + unsafe { *self.as_raw() }.group.try_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::from_raw(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_u16(),
>> + 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) -> Result<Group, &'static str> {
>> + self.0.group.try_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;
>> +}
>> +
>> +// SAFETY: `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.
>> +unsafe impl RawDeviceIdIndex for DeviceId {
>> + 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:
>> +// - `bindings::hid_driver` is a C type declared as `repr(C)`.
>> +// - `T` is the type of the driver's device private data.
>> +// - `struct hid_driver` embeds a `struct device_driver`.
>> +// - `DEVICE_DRIVER_OFFSET` is the correct byte offset to the embedded `struct device_driver`.
>> +unsafe impl<T: Driver + 'static> driver::DriverLayout for Adapter<T> {
>> + type DriverType = bindings::hid_driver;
>> + type DriverData = T;
>> + const DEVICE_DRIVER_OFFSET: usize = core::mem::offset_of!(Self::DriverType, driver);
>> +}
>> +
>> +// SAFETY: A call to `unregister` for a given instance of `DriverType` is guaranteed to be valid if
>> +// a preceding call to `register` has been successful.
>> +unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
>> + unsafe fn register(
>> + hdrv: &Opaque<Self::DriverType>,
>> + 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 `DriverType`
>> + to_result(unsafe {
>> + bindings::__hid_register_driver(hdrv.get(), module.0, name.as_char_ptr())
>> + })
>> + }
>> +
>> + unsafe fn unregister(hdrv: &Opaque<Self::DriverType>) {
>> + // SAFETY: `hdrv` is guaranteed to be a valid `DriverType`
>> + 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 3da92f18f4ee..e2dcacd9369e 100644
>> --- a/rust/kernel/lib.rs
>> +++ b/rust/kernel/lib.rs
>> @@ -102,6 +102,8 @@
>> pub mod id_pool;
>> #[doc(hidden)]
>> pub mod impl_flags;
>> +#[cfg(CONFIG_RUST_HID_ABSTRACTIONS)]
>> +pub mod hid;
>> pub mod init;
>> pub mod io;
>> pub mod ioctl;