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1// SPDX-License-Identifier: GPL-2.0
2
3//! Generic support for drivers of different buses (e.g., PCI, Platform, Amba, etc.).
4//!
5//! This documentation describes how to implement a bus specific driver API and how to align it with
6//! the design of (bus specific) devices.
7//!
8//! Note: Readers are expected to know the content of the documentation of [`Device`] and
9//! [`DeviceContext`].
10//!
11//! # Driver Trait
12//!
13//! The main driver interface is defined by a bus specific driver trait. For instance:
14//!
15//! ```ignore
16//! pub trait Driver: Send {
17//! /// The type holding information about each device ID supported by the driver.
18//! type IdInfo: 'static;
19//!
20//! /// The table of OF device ids supported by the driver.
21//! const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = None;
22//!
23//! /// The table of ACPI device ids supported by the driver.
24//! const ACPI_ID_TABLE: Option<acpi::IdTable<Self::IdInfo>> = None;
25//!
26//! /// Driver probe.
27//! fn probe(dev: &Device<device::Core>, id_info: &Self::IdInfo) -> impl PinInit<Self, Error>;
28//!
29//! /// Driver unbind (optional).
30//! fn unbind(dev: &Device<device::Core>, this: Pin<&Self>) {
31//! let _ = (dev, this);
32//! }
33//! }
34//! ```
35//!
36//! For specific examples see:
37//!
38//! * [`platform::Driver`](kernel::platform::Driver)
39#![cfg_attr(
40 CONFIG_AUXILIARY_BUS,
41 doc = "* [`auxiliary::Driver`](kernel::auxiliary::Driver)"
42)]
43#![cfg_attr(CONFIG_PCI, doc = "* [`pci::Driver`](kernel::pci::Driver)")]
44//!
45//! The `probe()` callback should return a `impl PinInit<Self, Error>`, i.e. the driver's private
46//! data. The bus abstraction should store the pointer in the corresponding bus device. The generic
47//! [`Device`] infrastructure provides common helpers for this purpose on its
48//! [`Device<CoreInternal>`] implementation.
49//!
50//! All driver callbacks should provide a reference to the driver's private data. Once the driver
51//! is unbound from the device, the bus abstraction should take back the ownership of the driver's
52//! private data from the corresponding [`Device`] and [`drop`] it.
53//!
54//! All driver callbacks should provide a [`Device<Core>`] reference (see also [`device::Core`]).
55//!
56//! # Adapter
57//!
58//! The adapter implementation of a bus represents the abstraction layer between the C bus
59//! callbacks and the Rust bus callbacks. It therefore has to be generic over an implementation of
60//! the [driver trait](#driver-trait).
61//!
62//! ```ignore
63//! pub struct Adapter<T: Driver>;
64//! ```
65//!
66//! There's a common [`Adapter`] trait that can be implemented to inherit common driver
67//! infrastructure, such as finding the ID info from an [`of::IdTable`] or [`acpi::IdTable`].
68//!
69//! # Driver Registration
70//!
71//! In order to register C driver types (such as `struct platform_driver`) the [adapter](#adapter)
72//! should implement the [`RegistrationOps`] trait.
73//!
74//! This trait implementation can be used to create the actual registration with the common
75//! [`Registration`] type.
76//!
77//! Typically, bus abstractions want to provide a bus specific `module_bus_driver!` macro, which
78//! creates a kernel module with exactly one [`Registration`] for the bus specific adapter.
79//!
80//! The generic driver infrastructure provides a helper for this with the [`module_driver`] macro.
81//!
82//! # Device IDs
83//!
84//! Besides the common device ID types, such as [`of::DeviceId`] and [`acpi::DeviceId`], most buses
85//! may need to implement their own device ID types.
86//!
87//! For this purpose the generic infrastructure in [`device_id`] should be used.
88//!
89//! [`Core`]: device::Core
90//! [`Device`]: device::Device
91//! [`Device<Core>`]: device::Device<device::Core>
92//! [`Device<CoreInternal>`]: device::Device<device::CoreInternal>
93//! [`DeviceContext`]: device::DeviceContext
94//! [`device_id`]: kernel::device_id
95//! [`module_driver`]: kernel::module_driver
96
97use crate::{
98 acpi,
99 device,
100 of,
101 prelude::*,
102 types::Opaque,
103 ThisModule, //
104};
105
106/// Trait describing the layout of a specific device driver.
107///
108/// This trait describes the layout of a specific driver structure, such as `struct pci_driver` or
109/// `struct platform_driver`.
110///
111/// # Safety
112///
113/// Implementors must guarantee that:
114/// - `DriverType` is `repr(C)`,
115/// - `DriverData` is the type of the driver's device private data.
116/// - `DriverType` embeds a valid `struct device_driver` at byte offset `DEVICE_DRIVER_OFFSET`.
117pub unsafe trait DriverLayout {
118 /// The specific driver type embedding a `struct device_driver`.
119 type DriverType: Default;
120
121 /// The type of the driver's device private data.
122 type DriverData;
123
124 /// Byte offset of the embedded `struct device_driver` within `DriverType`.
125 ///
126 /// This must correspond exactly to the location of the embedded `struct device_driver` field.
127 const DEVICE_DRIVER_OFFSET: usize;
128}
129
130/// The [`RegistrationOps`] trait serves as generic interface for subsystems (e.g., PCI, Platform,
131/// Amba, etc.) to provide the corresponding subsystem specific implementation to register /
132/// unregister a driver of the particular type (`DriverType`).
133///
134/// For instance, the PCI subsystem would set `DriverType` to `bindings::pci_driver` and call
135/// `bindings::__pci_register_driver` from `RegistrationOps::register` and
136/// `bindings::pci_unregister_driver` from `RegistrationOps::unregister`.
137///
138/// # Safety
139///
140/// A call to [`RegistrationOps::unregister`] for a given instance of `DriverType` is only valid if
141/// a preceding call to [`RegistrationOps::register`] has been successful.
142pub unsafe trait RegistrationOps: DriverLayout {
143 /// Registers a driver.
144 ///
145 /// # Safety
146 ///
147 /// On success, `reg` must remain pinned and valid until the matching call to
148 /// [`RegistrationOps::unregister`].
149 unsafe fn register(
150 reg: &Opaque<Self::DriverType>,
151 name: &'static CStr,
152 module: &'static ThisModule,
153 ) -> Result;
154
155 /// Unregisters a driver previously registered with [`RegistrationOps::register`].
156 ///
157 /// # Safety
158 ///
159 /// Must only be called after a preceding successful call to [`RegistrationOps::register`] for
160 /// the same `reg`.
161 unsafe fn unregister(reg: &Opaque<Self::DriverType>);
162}
163
164/// A [`Registration`] is a generic type that represents the registration of some driver type (e.g.
165/// `bindings::pci_driver`). Therefore a [`Registration`] must be initialized with a type that
166/// implements the [`RegistrationOps`] trait, such that the generic `T::register` and
167/// `T::unregister` calls result in the subsystem specific registration calls.
168///
169///Once the `Registration` structure is dropped, the driver is unregistered.
170#[pin_data(PinnedDrop)]
171pub struct Registration<T: RegistrationOps> {
172 #[pin]
173 reg: Opaque<T::DriverType>,
174}
175
176// SAFETY: `Registration` has no fields or methods accessible via `&Registration`, so it is safe to
177// share references to it with multiple threads as nothing can be done.
178unsafe impl<T: RegistrationOps> Sync for Registration<T> {}
179
180// SAFETY: Both registration and unregistration are implemented in C and safe to be performed from
181// any thread, so `Registration` is `Send`.
182unsafe impl<T: RegistrationOps> Send for Registration<T> {}
183
184impl<T: RegistrationOps + 'static> Registration<T> {
185 extern "C" fn post_unbind_callback(dev: *mut bindings::device) {
186 // SAFETY: The driver core only ever calls the post unbind callback with a valid pointer to
187 // a `struct device`.
188 //
189 // INVARIANT: `dev` is valid for the duration of the `post_unbind_callback()`.
190 let dev = unsafe { &*dev.cast::<device::Device<device::CoreInternal>>() };
191
192 // `remove()` and all devres callbacks have been completed at this point, hence drop the
193 // driver's device private data.
194 //
195 // SAFETY: By the safety requirements of the `Driver` trait, `T::DriverData` is the
196 // driver's device private data type.
197 drop(unsafe { dev.drvdata_obtain::<T::DriverData>() });
198 }
199
200 /// Attach generic `struct device_driver` callbacks.
201 fn callbacks_attach(drv: &Opaque<T::DriverType>) {
202 let ptr = drv.get().cast::<u8>();
203
204 // SAFETY:
205 // - `drv.get()` yields a valid pointer to `Self::DriverType`.
206 // - Adding `DEVICE_DRIVER_OFFSET` yields the address of the embedded `struct device_driver`
207 // as guaranteed by the safety requirements of the `Driver` trait.
208 let base = unsafe { ptr.add(T::DEVICE_DRIVER_OFFSET) };
209
210 // CAST: `base` points to the offset of the embedded `struct device_driver`.
211 let base = base.cast::<bindings::device_driver>();
212
213 // SAFETY: It is safe to set the fields of `struct device_driver` on initialization.
214 unsafe { (*base).p_cb.post_unbind_rust = Some(Self::post_unbind_callback) };
215 }
216
217 /// Creates a new instance of the registration object.
218 pub fn new(name: &'static CStr, module: &'static ThisModule) -> impl PinInit<Self, Error> {
219 try_pin_init!(Self {
220 reg <- Opaque::try_ffi_init(|ptr: *mut T::DriverType| {
221 // SAFETY: `try_ffi_init` guarantees that `ptr` is valid for write.
222 unsafe { ptr.write(T::DriverType::default()) };
223
224 // SAFETY: `try_ffi_init` guarantees that `ptr` is valid for write, and it has
225 // just been initialised above, so it's also valid for read.
226 let drv = unsafe { &*(ptr as *const Opaque<T::DriverType>) };
227
228 Self::callbacks_attach(drv);
229
230 // SAFETY: `drv` is guaranteed to be pinned until `T::unregister`.
231 unsafe { T::register(drv, name, module) }
232 }),
233 })
234 }
235}
236
237#[pinned_drop]
238impl<T: RegistrationOps> PinnedDrop for Registration<T> {
239 fn drop(self: Pin<&mut Self>) {
240 // SAFETY: The existence of `self` guarantees that `self.reg` has previously been
241 // successfully registered with `T::register`
242 unsafe { T::unregister(&self.reg) };
243 }
244}
245
246/// Declares a kernel module that exposes a single driver.
247///
248/// It is meant to be used as a helper by other subsystems so they can more easily expose their own
249/// macros.
250#[macro_export]
251macro_rules! module_driver {
252 (<$gen_type:ident>, $driver_ops:ty, { type: $type:ty, $($f:tt)* }) => {
253 type Ops<$gen_type> = $driver_ops;
254
255 #[$crate::prelude::pin_data]
256 struct DriverModule {
257 #[pin]
258 _driver: $crate::driver::Registration<Ops<$type>>,
259 }
260
261 impl $crate::InPlaceModule for DriverModule {
262 fn init(
263 module: &'static $crate::ThisModule
264 ) -> impl ::pin_init::PinInit<Self, $crate::error::Error> {
265 $crate::try_pin_init!(Self {
266 _driver <- $crate::driver::Registration::new(
267 <Self as $crate::ModuleMetadata>::NAME,
268 module,
269 ),
270 })
271 }
272 }
273
274 $crate::prelude::module! {
275 type: DriverModule,
276 $($f)*
277 }
278 }
279}
280
281/// The bus independent adapter to match a drivers and a devices.
282///
283/// This trait should be implemented by the bus specific adapter, which represents the connection
284/// of a device and a driver.
285///
286/// It provides bus independent functions for device / driver interactions.
287pub trait Adapter {
288 /// The type holding driver private data about each device id supported by the driver.
289 type IdInfo: 'static;
290
291 /// The [`acpi::IdTable`] of the corresponding driver
292 fn acpi_id_table() -> Option<acpi::IdTable<Self::IdInfo>>;
293
294 /// Returns the driver's private data from the matching entry in the [`acpi::IdTable`], if any.
295 ///
296 /// If this returns `None`, it means there is no match with an entry in the [`acpi::IdTable`].
297 fn acpi_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
298 #[cfg(not(CONFIG_ACPI))]
299 {
300 let _ = dev;
301 None
302 }
303
304 #[cfg(CONFIG_ACPI)]
305 {
306 let table = Self::acpi_id_table()?;
307
308 // SAFETY:
309 // - `table` has static lifetime, hence it's valid for read,
310 // - `dev` is guaranteed to be valid while it's alive, and so is `dev.as_raw()`.
311 let raw_id = unsafe { bindings::acpi_match_device(table.as_ptr(), dev.as_raw()) };
312
313 if raw_id.is_null() {
314 None
315 } else {
316 // SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `struct acpi_device_id`
317 // and does not add additional invariants, so it's safe to transmute.
318 let id = unsafe { &*raw_id.cast::<acpi::DeviceId>() };
319
320 Some(table.info(<acpi::DeviceId as crate::device_id::RawDeviceIdIndex>::index(id)))
321 }
322 }
323 }
324
325 /// The [`of::IdTable`] of the corresponding driver.
326 fn of_id_table() -> Option<of::IdTable<Self::IdInfo>>;
327
328 /// Returns the driver's private data from the matching entry in the [`of::IdTable`], if any.
329 ///
330 /// If this returns `None`, it means there is no match with an entry in the [`of::IdTable`].
331 fn of_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
332 #[cfg(not(CONFIG_OF))]
333 {
334 let _ = dev;
335 None
336 }
337
338 #[cfg(CONFIG_OF)]
339 {
340 let table = Self::of_id_table()?;
341
342 // SAFETY:
343 // - `table` has static lifetime, hence it's valid for read,
344 // - `dev` is guaranteed to be valid while it's alive, and so is `dev.as_raw()`.
345 let raw_id = unsafe { bindings::of_match_device(table.as_ptr(), dev.as_raw()) };
346
347 if raw_id.is_null() {
348 None
349 } else {
350 // SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `struct of_device_id`
351 // and does not add additional invariants, so it's safe to transmute.
352 let id = unsafe { &*raw_id.cast::<of::DeviceId>() };
353
354 Some(
355 table.info(<of::DeviceId as crate::device_id::RawDeviceIdIndex>::index(
356 id,
357 )),
358 )
359 }
360 }
361 }
362
363 /// Returns the driver's private data from the matching entry of any of the ID tables, if any.
364 ///
365 /// If this returns `None`, it means that there is no match in any of the ID tables directly
366 /// associated with a [`device::Device`].
367 fn id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
368 let id = Self::acpi_id_info(dev);
369 if id.is_some() {
370 return id;
371 }
372
373 let id = Self::of_id_info(dev);
374 if id.is_some() {
375 return id;
376 }
377
378 None
379 }
380}