1// SPDX-License-Identifier: GPL-2.0
2
3//! Abstractions for the platform bus.
4//!
5//! C header: [`include/linux/platform_device.h`](srctree/include/linux/platform_device.h)
6
7use crate::{
8 bindings, container_of, device, driver,
9 error::{to_result, Result},
10 of,
11 prelude::*,
12 str::CStr,
13 types::{ForeignOwnable, Opaque},
14 ThisModule,
15};
16
17use core::{
18 marker::PhantomData,
19 ptr::{addr_of_mut, NonNull},
20};
21
22/// An adapter for the registration of platform drivers.
23pub struct Adapter<T: Driver>(T);
24
25// SAFETY: A call to `unregister` for a given instance of `RegType` is guaranteed to be valid if
26// a preceding call to `register` has been successful.
27unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
28 type RegType = bindings::platform_driver;
29
30 unsafe fn register(
31 pdrv: &Opaque<Self::RegType>,
32 name: &'static CStr,
33 module: &'static ThisModule,
34 ) -> Result {
35 let of_table = match T::OF_ID_TABLE {
36 Some(table) => table.as_ptr(),
37 None => core::ptr::null(),
38 };
39
40 // SAFETY: It's safe to set the fields of `struct platform_driver` on initialization.
41 unsafe {
42 (*pdrv.get()).driver.name = name.as_char_ptr();
43 (*pdrv.get()).probe = Some(Self::probe_callback);
44 (*pdrv.get()).remove = Some(Self::remove_callback);
45 (*pdrv.get()).driver.of_match_table = of_table;
46 }
47
48 // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
49 to_result(unsafe { bindings::__platform_driver_register(pdrv.get(), module.0) })
50 }
51
52 unsafe fn unregister(pdrv: &Opaque<Self::RegType>) {
53 // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
54 unsafe { bindings::platform_driver_unregister(pdrv.get()) };
55 }
56}
57
58impl<T: Driver + 'static> Adapter<T> {
59 extern "C" fn probe_callback(pdev: *mut bindings::platform_device) -> kernel::ffi::c_int {
60 // SAFETY: The platform bus only ever calls the probe callback with a valid pointer to a
61 // `struct platform_device`.
62 //
63 // INVARIANT: `pdev` is valid for the duration of `probe_callback()`.
64 let pdev = unsafe { &*pdev.cast::<Device<device::Core>>() };
65
66 let info = <Self as driver::Adapter>::id_info(pdev.as_ref());
67 match T::probe(pdev, info) {
68 Ok(data) => {
69 // Let the `struct platform_device` own a reference of the driver's private data.
70 // SAFETY: By the type invariant `pdev.as_raw` returns a valid pointer to a
71 // `struct platform_device`.
72 unsafe { bindings::platform_set_drvdata(pdev.as_raw(), data.into_foreign() as _) };
73 }
74 Err(err) => return Error::to_errno(err),
75 }
76
77 0
78 }
79
80 extern "C" fn remove_callback(pdev: *mut bindings::platform_device) {
81 // SAFETY: `pdev` is a valid pointer to a `struct platform_device`.
82 let ptr = unsafe { bindings::platform_get_drvdata(pdev) }.cast();
83
84 // SAFETY: `remove_callback` is only ever called after a successful call to
85 // `probe_callback`, hence it's guaranteed that `ptr` points to a valid and initialized
86 // `KBox<T>` pointer created through `KBox::into_foreign`.
87 let _ = unsafe { KBox::<T>::from_foreign(ptr) };
88 }
89}
90
91impl<T: Driver + 'static> driver::Adapter for Adapter<T> {
92 type IdInfo = T::IdInfo;
93
94 fn of_id_table() -> Option<of::IdTable<Self::IdInfo>> {
95 T::OF_ID_TABLE
96 }
97}
98
99/// Declares a kernel module that exposes a single platform driver.
100///
101/// # Examples
102///
103/// ```ignore
104/// kernel::module_platform_driver! {
105/// type: MyDriver,
106/// name: "Module name",
107/// authors: ["Author name"],
108/// description: "Description",
109/// license: "GPL v2",
110/// }
111/// ```
112#[macro_export]
113macro_rules! module_platform_driver {
114 ($($f:tt)*) => {
115 $crate::module_driver!(<T>, $crate::platform::Adapter<T>, { $($f)* });
116 };
117}
118
119/// The platform driver trait.
120///
121/// Drivers must implement this trait in order to get a platform driver registered.
122///
123/// # Example
124///
125///```
126/// # use kernel::{bindings, c_str, device::Core, of, platform};
127///
128/// struct MyDriver;
129///
130/// kernel::of_device_table!(
131/// OF_TABLE,
132/// MODULE_OF_TABLE,
133/// <MyDriver as platform::Driver>::IdInfo,
134/// [
135/// (of::DeviceId::new(c_str!("test,device")), ())
136/// ]
137/// );
138///
139/// impl platform::Driver for MyDriver {
140/// type IdInfo = ();
141/// const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
142///
143/// fn probe(
144/// _pdev: &platform::Device<Core>,
145/// _id_info: Option<&Self::IdInfo>,
146/// ) -> Result<Pin<KBox<Self>>> {
147/// Err(ENODEV)
148/// }
149/// }
150///```
151pub trait Driver: Send {
152 /// The type holding driver private data about each device id supported by the driver.
153 // TODO: Use associated_type_defaults once stabilized:
154 //
155 // ```
156 // type IdInfo: 'static = ();
157 // ```
158 type IdInfo: 'static;
159
160 /// The table of OF device ids supported by the driver.
161 const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>>;
162
163 /// Platform driver probe.
164 ///
165 /// Called when a new platform device is added or discovered.
166 /// Implementers should attempt to initialize the device here.
167 fn probe(dev: &Device<device::Core>, id_info: Option<&Self::IdInfo>)
168 -> Result<Pin<KBox<Self>>>;
169}
170
171/// The platform device representation.
172///
173/// This structure represents the Rust abstraction for a C `struct platform_device`. The
174/// implementation abstracts the usage of an already existing C `struct platform_device` within Rust
175/// code that we get passed from the C side.
176///
177/// # Invariants
178///
179/// A [`Device`] instance represents a valid `struct platform_device` created by the C portion of
180/// the kernel.
181#[repr(transparent)]
182pub struct Device<Ctx: device::DeviceContext = device::Normal>(
183 Opaque<bindings::platform_device>,
184 PhantomData<Ctx>,
185);
186
187impl<Ctx: device::DeviceContext> Device<Ctx> {
188 fn as_raw(&self) -> *mut bindings::platform_device {
189 self.0.get()
190 }
191}
192
193// SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
194// argument.
195kernel::impl_device_context_deref!(unsafe { Device });
196kernel::impl_device_context_into_aref!(Device);
197
198// SAFETY: Instances of `Device` are always reference-counted.
199unsafe impl crate::types::AlwaysRefCounted for Device {
200 fn inc_ref(&self) {
201 // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
202 unsafe { bindings::get_device(self.as_ref().as_raw()) };
203 }
204
205 unsafe fn dec_ref(obj: NonNull<Self>) {
206 // SAFETY: The safety requirements guarantee that the refcount is non-zero.
207 unsafe { bindings::platform_device_put(obj.cast().as_ptr()) }
208 }
209}
210
211impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
212 fn as_ref(&self) -> &device::Device<Ctx> {
213 // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
214 // `struct platform_device`.
215 let dev = unsafe { addr_of_mut!((*self.as_raw()).dev) };
216
217 // SAFETY: `dev` points to a valid `struct device`.
218 unsafe { device::Device::as_ref(dev) }
219 }
220}
221
222impl<Ctx: device::DeviceContext> TryFrom<&device::Device<Ctx>> for &Device<Ctx> {
223 type Error = kernel::error::Error;
224
225 fn try_from(dev: &device::Device<Ctx>) -> Result<Self, Self::Error> {
226 // SAFETY: By the type invariant of `Device`, `dev.as_raw()` is a valid pointer to a
227 // `struct device`.
228 if !unsafe { bindings::dev_is_platform(dev.as_raw()) } {
229 return Err(EINVAL);
230 }
231
232 // SAFETY: We've just verified that the bus type of `dev` equals
233 // `bindings::platform_bus_type`, hence `dev` must be embedded in a valid
234 // `struct platform_device` as guaranteed by the corresponding C code.
235 let pdev = unsafe { container_of!(dev.as_raw(), bindings::platform_device, dev) };
236
237 // SAFETY: `pdev` is a valid pointer to a `struct platform_device`.
238 Ok(unsafe { &*pdev.cast() })
239 }
240}
241
242// SAFETY: A `Device` is always reference-counted and can be released from any thread.
243unsafe impl Send for Device {}
244
245// SAFETY: `Device` can be shared among threads because all methods of `Device`
246// (i.e. `Device<Normal>) are thread safe.
247unsafe impl Sync for Device {}
248

source code of linux/rust/kernel/platform.rs

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