Add basic USB abstractions, consisting of usb::{Device, Interface,
Driver, Adapter, DeviceId} and the module_usb_driver macro. This is the
first step in being able to write USB device drivers, which paves the
way for USB media drivers - for example - among others.
This initial support will then be used by a subsequent sample driver,
which constitutes the only user of the USB abstractions so far.
Signed-off-by: Daniel Almeida <daniel.almeida@xxxxxxxxxxxxx>
---
rust/bindings/bindings_helper.h | 1 +
rust/helpers/helpers.c | 1 +
rust/helpers/usb.c | 8 +
rust/kernel/lib.rs | 2 +
rust/kernel/usb.rs | 457 ++++++++++++++++++++++++++++++++++++++++
5 files changed, 469 insertions(+)
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 69a975da829f0c35760f71a1b32b8fcb12c8a8dc..645afe578668097ae04455d9eefb102d1f1ce4af 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -73,6 +73,7 @@
#include <linux/security.h>
#include <linux/slab.h>
#include <linux/tracepoint.h>
+#include <linux/usb.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
#include <linux/xarray.h>
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 44b2005d50140d34a44ae37d01c2ddbae6aeaa32..da1ee0d3705739e789c7ad21b957bbdb7ca23521 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -48,6 +48,7 @@
#include "task.c"
#include "time.c"
#include "uaccess.c"
+#include "usb.c"
#include "vmalloc.c"
#include "wait.c"
#include "workqueue.c"
diff --git a/rust/helpers/usb.c b/rust/helpers/usb.c
new file mode 100644
index 0000000000000000000000000000000000000000..fb2aad0cbf4d26ac7fb1a3f176ee7a1d30800f92
--- /dev/null
+++ b/rust/helpers/usb.c
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/usb.h>
+
+struct usb_device *rust_helper_interface_to_usbdev(struct usb_interface *intf)
+{
+ return interface_to_usbdev(intf);
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index f8db761c5c95fc66e4c55f539b17fca613161ada..b15277a02028aa1d27480d0630f9f599cacd6e4d 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -127,6 +127,8 @@
pub mod tracepoint;
pub mod transmute;
pub mod types;
+#[cfg(CONFIG_USB)]
+pub mod usb;
pub mod uaccess;
pub mod workqueue;
pub mod xarray;
diff --git a/rust/kernel/usb.rs b/rust/kernel/usb.rs
new file mode 100644
index 0000000000000000000000000000000000000000..8899e7520b58d4e4b08927d54c8912650b78da33
--- /dev/null
+++ b/rust/kernel/usb.rs
@@ -0,0 +1,457 @@
+// SPDX-License-Identifier: GPL-2.0
+// SPDX-FileCopyrightText: Copyright (C) 2025 Collabora Ltd.
+
+//! Abstractions for the USB bus.
+//!
+//! C header: [`include/linux/usb.h`](srctree/include/linux/usb.h)
+
+use crate::{
+ bindings, device,
+ device_id::{RawDeviceId, RawDeviceIdIndex},
+ driver,
+ error::{from_result, to_result, Result},
+ prelude::*,
+ str::CStr,
+ types::{AlwaysRefCounted, Opaque},
+ ThisModule,
+};
+use core::{marker::PhantomData, mem::MaybeUninit, ptr::NonNull};
+
+/// An adapter for the registration of USB 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::usb_driver;
+
+ unsafe fn register(
+ udrv: &Opaque<Self::RegType>,
+ name: &'static CStr,
+ module: &'static ThisModule,
+ ) -> Result {
+ // SAFETY: It's safe to set the fields of `struct usb_driver` on initialization.
+ unsafe {
+ (*udrv.get()).name = name.as_char_ptr();
+ (*udrv.get()).probe = Some(Self::probe_callback);
+ (*udrv.get()).disconnect = Some(Self::disconnect_callback);
+ (*udrv.get()).id_table = T::ID_TABLE.as_ptr();
+ }
+
+ // SAFETY: `udrv` is guaranteed to be a valid `RegType`.
+ to_result(unsafe {
+ bindings::usb_register_driver(udrv.get(), module.0, name.as_char_ptr())
+ })
+ }
+
+ unsafe fn unregister(udrv: &Opaque<Self::RegType>) {
+ // SAFETY: `udrv` is guaranteed to be a valid `RegType`.
+ unsafe { bindings::usb_deregister(udrv.get()) };
+ }
+}
+
+impl<T: Driver + 'static> Adapter<T> {
+ extern "C" fn probe_callback(
+ intf: *mut bindings::usb_interface,
+ id: *const bindings::usb_device_id,
+ ) -> kernel::ffi::c_int {
+ // SAFETY: The USB core only ever calls the probe callback with a valid pointer to a
+ // `struct usb_interface` and `struct usb_device_id`.
+ //
+ // INVARIANT: `intf` is valid for the duration of `probe_callback()`.
+ let intf = unsafe { &*intf.cast::<Interface<device::CoreInternal>>() };
+
+ from_result(|| {
+ // SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `struct usb_device_id` and
+ // does not add additional invariants, so it's safe to transmute.
+ let id = unsafe { &*id.cast::<DeviceId>() };
+
+ let info = T::ID_TABLE.info(id.index());
+ let data = T::probe(intf, id, info)?;
+
+ let dev: &device::Device<device::CoreInternal> = intf.as_ref();
+ dev.set_drvdata(data);
+ Ok(0)
+ })
+ }
+
+ extern "C" fn disconnect_callback(intf: *mut bindings::usb_interface) {
+ // SAFETY: The USB core only ever calls the disconnect callback with a valid pointer to a
+ // `struct usb_interface`.
+ //
+ // INVARIANT: `intf` is valid for the duration of `disconnect_callback()`.
+ let intf = unsafe { &*intf.cast::<Interface<device::CoreInternal>>() };
+
+ let dev: &device::Device<device::CoreInternal> = intf.as_ref();
+
+ // SAFETY: `disconnect_callback` is only ever called after a successful call to
+ // `probe_callback`, hence it's guaranteed that `Device::set_drvdata()` has been called
+ // and stored a `Pin<KBox<T>>`.
+ let data = unsafe { dev.drvdata_obtain::<Pin<KBox<T>>>() };
+
+ T::disconnect(intf, data.as_ref());
+ }
+}
+
+/// Abstraction for the USB device ID structure, i.e. [`struct usb_device_id`].
+///
+/// [`struct usb_device_id`]: https://docs.kernel.org/driver-api/basics.html#c.usb_device_id
+#[repr(transparent)]
+#[derive(Clone, Copy)]
+pub struct DeviceId(bindings::usb_device_id);
+
+impl DeviceId {
+ /// Equivalent to C's `USB_DEVICE` macro.
+ pub const fn from_id(vendor: u16, product: u16) -> Self {
+ Self(bindings::usb_device_id {
+ match_flags: bindings::USB_DEVICE_ID_MATCH_DEVICE as u16,
+ idVendor: vendor,
+ idProduct: product,
+ // SAFETY: It is safe to use all zeroes for the other fields of `usb_device_id`.
+ ..unsafe { MaybeUninit::zeroed().assume_init() }
+ })
+ }
+
+ /// Equivalent to C's `USB_DEVICE_VER` macro.
+ pub const fn from_device_ver(vendor: u16, product: u16, bcd_lo: u16, bcd_hi: u16) -> Self {
+ Self(bindings::usb_device_id {
+ match_flags: bindings::USB_DEVICE_ID_MATCH_DEVICE_AND_VERSION as u16,
+ idVendor: vendor,
+ idProduct: product,
+ bcdDevice_lo: bcd_lo,
+ bcdDevice_hi: bcd_hi,
+ // SAFETY: It is safe to use all zeroes for the other fields of `usb_device_id`.
+ ..unsafe { MaybeUninit::zeroed().assume_init() }
+ })
+ }
+
+ /// Equivalent to C's `USB_DEVICE_INFO` macro.
+ pub const fn from_device_info(class: u8, subclass: u8, protocol: u8) -> Self {
+ Self(bindings::usb_device_id {
+ match_flags: bindings::USB_DEVICE_ID_MATCH_DEV_INFO as u16,
+ bDeviceClass: class,
+ bDeviceSubClass: subclass,
+ bDeviceProtocol: protocol,
+ // SAFETY: It is safe to use all zeroes for the other fields of `usb_device_id`.
+ ..unsafe { MaybeUninit::zeroed().assume_init() }
+ })
+ }
+
+ /// Equivalent to C's `USB_INTERFACE_INFO` macro.
+ pub const fn from_interface_info(class: u8, subclass: u8, protocol: u8) -> Self {
+ Self(bindings::usb_device_id {
+ match_flags: bindings::USB_DEVICE_ID_MATCH_INT_INFO as u16,
+ bInterfaceClass: class,
+ bInterfaceSubClass: subclass,
+ bInterfaceProtocol: protocol,
+ // SAFETY: It is safe to use all zeroes for the other fields of `usb_device_id`.
+ ..unsafe { MaybeUninit::zeroed().assume_init() }
+ })
+ }
+
+ /// Equivalent to C's `USB_DEVICE_INTERFACE_CLASS` macro.
+ pub const fn from_device_interface_class(vendor: u16, product: u16, class: u8) -> Self {
+ Self(bindings::usb_device_id {
+ match_flags: (bindings::USB_DEVICE_ID_MATCH_DEVICE
+ | bindings::USB_DEVICE_ID_MATCH_INT_CLASS) as u16,
+ idVendor: vendor,
+ idProduct: product,
+ bInterfaceClass: class,
+ // SAFETY: It is safe to use all zeroes for the other fields of `usb_device_id`.
+ ..unsafe { MaybeUninit::zeroed().assume_init() }
+ })
+ }
+
+ /// Equivalent to C's `USB_DEVICE_INTERFACE_PROTOCOL` macro.
+ pub const fn from_device_interface_protocol(vendor: u16, product: u16, protocol: u8) -> Self {
+ Self(bindings::usb_device_id {
+ match_flags: (bindings::USB_DEVICE_ID_MATCH_DEVICE
+ | bindings::USB_DEVICE_ID_MATCH_INT_PROTOCOL) as u16,
+ idVendor: vendor,
+ idProduct: product,
+ bInterfaceProtocol: protocol,
+ // SAFETY: It is safe to use all zeroes for the other fields of `usb_device_id`.
+ ..unsafe { MaybeUninit::zeroed().assume_init() }
+ })
+ }
+
+ /// Equivalent to C's `USB_DEVICE_INTERFACE_NUMBER` macro.
+ pub const fn from_device_interface_number(vendor: u16, product: u16, number: u8) -> Self {
+ Self(bindings::usb_device_id {
+ match_flags: (bindings::USB_DEVICE_ID_MATCH_DEVICE
+ | bindings::USB_DEVICE_ID_MATCH_INT_NUMBER) as u16,
+ idVendor: vendor,
+ idProduct: product,
+ bInterfaceNumber: number,
+ // SAFETY: It is safe to use all zeroes for the other fields of `usb_device_id`.
+ ..unsafe { MaybeUninit::zeroed().assume_init() }
+ })
+ }
+
+ /// Equivalent to C's `USB_DEVICE_AND_INTERFACE_INFO` macro.
+ pub const fn from_device_and_interface_info(
+ vendor: u16,
+ product: u16,
+ class: u8,
+ subclass: u8,
+ protocol: u8,
+ ) -> Self {
+ Self(bindings::usb_device_id {
+ match_flags: (bindings::USB_DEVICE_ID_MATCH_INT_INFO
+ | bindings::USB_DEVICE_ID_MATCH_DEVICE) as u16,
+ idVendor: vendor,
+ idProduct: product,
+ bInterfaceClass: class,
+ bInterfaceSubClass: subclass,
+ bInterfaceProtocol: protocol,
+ // SAFETY: It is safe to use all zeroes for the other fields of `usb_device_id`.
+ ..unsafe { MaybeUninit::zeroed().assume_init() }
+ })
+ }
+}
+
+// SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `usb_device_id` and does not add
+// additional invariants, so it's safe to transmute to `RawType`.
+unsafe impl RawDeviceId for DeviceId {
+ type RawType = bindings::usb_device_id;
+}
+
+// SAFETY: `DRIVER_DATA_OFFSET` is the offset to the `driver_info` field.
+unsafe impl RawDeviceIdIndex for DeviceId {
+ const DRIVER_DATA_OFFSET: usize = core::mem::offset_of!(bindings::usb_device_id, driver_info);
+
+ fn index(&self) -> usize {
+ self.0.driver_info
+ }
+}
+
+/// [`IdTable`](kernel::device_id::IdTable) type for USB.
+pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>;
+
+/// Create a USB `IdTable` with its alias for modpost.
+#[macro_export]
+macro_rules! usb_device_table {
+ ($table_name:ident, $module_table_name:ident, $id_info_type: ty, $table_data: expr) => {
+ const $table_name: $crate::device_id::IdArray<
+ $crate::usb::DeviceId,
+ $id_info_type,
+ { $table_data.len() },
+ > = $crate::device_id::IdArray::new($table_data);
+
+ $crate::module_device_table!("usb", $module_table_name, $table_name);
+ };
+}
+
+/// The USB driver trait.
+///
+/// # Examples
+///
+///```
+/// # use kernel::{bindings, device::Core, usb};
+/// use kernel::prelude::*;
+///
+/// struct MyDriver;
+///
+/// kernel::usb_device_table!(
+/// USB_TABLE,
+/// MODULE_USB_TABLE,
+/// <MyDriver as usb::Driver>::IdInfo,
+/// [
+/// (usb::DeviceId::from_id(0x1234, 0x5678), ()),
+/// (usb::DeviceId::from_id(0xabcd, 0xef01), ()),
+/// ]
+/// );
+///
+/// impl usb::Driver for MyDriver {
+/// type IdInfo = ();
+/// const ID_TABLE: usb::IdTable<Self::IdInfo> = &USB_TABLE;
+///
+/// fn probe(
+/// _interface: &usb::Interface<Core>,
+/// _id: &usb::DeviceId,
+/// _info: &Self::IdInfo,
+/// ) -> Result<Pin<KBox<Self>>> {
+/// Err(ENODEV)
+/// }
+///
+/// fn disconnect(_interface: &usb::Interface<Core>, _data: Pin<&Self>) {}
+/// }
+///```
+pub trait Driver {
+ /// The type holding information about each one of the device ids supported by the driver.
+ type IdInfo: 'static;
+
+ /// The table of device ids supported by the driver.
+ const ID_TABLE: IdTable<Self::IdInfo>;
+
+ /// USB driver probe.
+ ///
+ /// Called when a new USB interface is bound to this driver.
+ /// Implementers should attempt to initialize the interface here.
+ fn probe(
+ interface: &Interface<device::Core>,
+ id: &DeviceId,
+ id_info: &Self::IdInfo,
+ ) -> Result<Pin<KBox<Self>>>;
+
+ /// USB driver disconnect.
+ ///
+ /// Called when the USB interface is about to be unbound from this driver.
+ fn disconnect(interface: &Interface<device::Core>, data: Pin<&Self>);
+}
+
+/// A USB interface.
+///
+/// This structure represents the Rust abstraction for a C [`struct usb_interface`].
+/// The implementation abstracts the usage of a C [`struct usb_interface`] passed
+/// in from the C side.
+///
+/// # Invariants
+///
+/// An [`Interface`] instance represents a valid [`struct usb_interface`] created
+/// by the C portion of the kernel.
+///
+/// [`struct usb_interface`]: https://www.kernel.org/doc/html/latest/driver-api/usb/usb.html#c.usb_interface
+#[repr(transparent)]
+pub struct Interface<Ctx: device::DeviceContext = device::Normal>(
+ Opaque<bindings::usb_interface>,
+ PhantomData<Ctx>,
+);
+
+impl<Ctx: device::DeviceContext> Interface<Ctx> {
+ fn as_raw(&self) -> *mut bindings::usb_interface {
+ self.0.get()
+ }
+}
+
+// SAFETY: `Interface` is a transparent wrapper of a type that doesn't depend on
+// `Interface`'s generic argument.
+kernel::impl_device_context_deref!(unsafe { Interface });
+kernel::impl_device_context_into_aref!(Interface);
+
+impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Interface<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 usb_interface`.
+ let dev = unsafe { &raw mut ((*self.as_raw()).dev) };
+
+ // SAFETY: `dev` points to a valid `struct device`.
+ unsafe { device::Device::from_raw(dev) }
+ }
+}
+
+impl<Ctx: device::DeviceContext> AsRef<Device<Ctx>> for Interface<Ctx> {
+ fn as_ref(&self) -> &Device<Ctx> {
+ // SAFETY: `self.as_raw()` is valid by the type invariants. For a valid interface,
+ // the helper should always return a valid USB device pointer.
+ let usb_dev = unsafe { bindings::interface_to_usbdev(self.as_raw()) };
+
+ // SAFETY: The helper returns a valid interface pointer that shares the
+ // same `DeviceContext`.
+ unsafe { &*(usb_dev.cast()) }
+ }
+}
+
+// SAFETY: Instances of `Interface` are always reference-counted.
+unsafe impl AlwaysRefCounted for Interface {
+ fn inc_ref(&self) {
+ // SAFETY: The invariants of `Interface` guarantee that `self.as_raw()`
+ // returns a valid `struct usb_interface` pointer, for which we will
+ // acquire a new refcount.
+ unsafe { bindings::usb_get_intf(self.as_raw()) };
+ }
+
+ unsafe fn dec_ref(obj: NonNull<Self>) {
+ // SAFETY: The safety requirements guarantee that the refcount is non-zero.
+ unsafe { bindings::usb_put_intf(obj.cast().as_ptr()) }
+ }
+}
+
+// SAFETY: A `Interface` is always reference-counted and can be released from any thread.
+unsafe impl Send for Interface {}
+
+// SAFETY: It is safe to send a &Interface to another thread because we do not
+// allow any mutation through a shared reference.
+unsafe impl Sync for Interface {}
+
+/// A USB device.
+///
+/// This structure represents the Rust abstraction for a C [`struct usb_device`].
+/// The implementation abstracts the usage of a C [`struct usb_device`] passed in
+/// from the C side.
+///
+/// # Invariants
+///
+/// A [`Device`] instance represents a valid [`struct usb_device`] created by the C portion of the
+/// kernel.
+///
+/// [`struct usb_device`]: https://www.kernel.org/doc/html/latest/driver-api/usb/usb.html#c.usb_device
+#[repr(transparent)]
+pub struct Device<Ctx: device::DeviceContext = device::Normal>(
+ Opaque<bindings::usb_device>,
+ PhantomData<Ctx>,
+);
+
+impl<Ctx: device::DeviceContext> Device<Ctx> {
+ fn as_raw(&self) -> *mut bindings::usb_device {
+ self.0.get()
+ }
+}
+
+// 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 AlwaysRefCounted for Device {
+ fn inc_ref(&self) {
+ // SAFETY: The invariants of `Device` guarantee that `self.as_raw()`
+ // returns a valid `struct usb_device` pointer, for which we will
+ // acquire a new refcount.
+ unsafe { bindings::usb_get_dev(self.as_raw()) };
+ }
+
+ unsafe fn dec_ref(obj: NonNull<Self>) {
+ // SAFETY: The safety requirements guarantee that the refcount is non-zero.
+ unsafe { bindings::usb_put_dev(obj.cast().as_ptr()) }
+ }
+}
+
+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 usb_device`.
+ let dev = unsafe { &raw mut ((*self.as_raw()).dev) };
+
+ // SAFETY: `dev` points to a valid `struct device`.
+ unsafe { device::Device::from_raw(dev) }
+ }
+}
+
+// SAFETY: A `Device` is always reference-counted and can be released from any thread.
+unsafe impl Send for Device {}
+
+// SAFETY: It is safe to send a &Device to another thread because we do not
+// allow any mutation through a shared reference.
+unsafe impl Sync for Device {}
+
+/// Declares a kernel module that exposes a single USB driver.
+///
+/// # Examples
+///
+/// ```ignore
+/// module_usb_driver! {
+/// type: MyDriver,
+/// name: "Module name",
+/// author: ["Author name"],
+/// description: "Description",
+/// license: "GPL v2",
+/// }
+/// ```
+#[macro_export]
+macro_rules! module_usb_driver {
+ ($($f:tt)*) => {
+ $crate::module_driver!(<T>, $crate::usb::Adapter<T>, { $($f)* });
+ }
+}
--
2.50.1
