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Diffstat (limited to 'rust/kernel/platform.rs')
| -rw-r--r-- | rust/kernel/platform.rs | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs new file mode 100644 index 000000000000..50e6b0421813 --- /dev/null +++ b/rust/kernel/platform.rs @@ -0,0 +1,200 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Abstractions for the platform bus. +//! +//! C header: [`include/linux/platform_device.h`](srctree/include/linux/platform_device.h) + +use crate::{ + bindings, container_of, device, driver, + error::{to_result, Result}, + of, + prelude::*, + str::CStr, + types::{ARef, ForeignOwnable, Opaque}, + ThisModule, +}; + +use core::ptr::addr_of_mut; + +/// An adapter for the registration of platform 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::platform_driver; + + unsafe fn register( + pdrv: &Opaque<Self::RegType>, + name: &'static CStr, + module: &'static ThisModule, + ) -> Result { + let of_table = match T::OF_ID_TABLE { + Some(table) => table.as_ptr(), + None => core::ptr::null(), + }; + + // SAFETY: It's safe to set the fields of `struct platform_driver` on initialization. + unsafe { + (*pdrv.get()).driver.name = name.as_char_ptr(); + (*pdrv.get()).probe = Some(Self::probe_callback); + (*pdrv.get()).remove = Some(Self::remove_callback); + (*pdrv.get()).driver.of_match_table = of_table; + } + + // SAFETY: `pdrv` is guaranteed to be a valid `RegType`. + to_result(unsafe { bindings::__platform_driver_register(pdrv.get(), module.0) }) + } + + unsafe fn unregister(pdrv: &Opaque<Self::RegType>) { + // SAFETY: `pdrv` is guaranteed to be a valid `RegType`. + unsafe { bindings::platform_driver_unregister(pdrv.get()) }; + } +} + +impl<T: Driver + 'static> Adapter<T> { + extern "C" fn probe_callback(pdev: *mut bindings::platform_device) -> kernel::ffi::c_int { + // SAFETY: The platform bus only ever calls the probe callback with a valid `pdev`. + let dev = unsafe { device::Device::get_device(addr_of_mut!((*pdev).dev)) }; + // SAFETY: `dev` is guaranteed to be embedded in a valid `struct platform_device` by the + // call above. + let mut pdev = unsafe { Device::from_dev(dev) }; + + let info = <Self as driver::Adapter>::id_info(pdev.as_ref()); + match T::probe(&mut pdev, info) { + Ok(data) => { + // Let the `struct platform_device` own a reference of the driver's private data. + // SAFETY: By the type invariant `pdev.as_raw` returns a valid pointer to a + // `struct platform_device`. + unsafe { bindings::platform_set_drvdata(pdev.as_raw(), data.into_foreign() as _) }; + } + Err(err) => return Error::to_errno(err), + } + + 0 + } + + extern "C" fn remove_callback(pdev: *mut bindings::platform_device) { + // SAFETY: `pdev` is a valid pointer to a `struct platform_device`. + let ptr = unsafe { bindings::platform_get_drvdata(pdev) }; + + // SAFETY: `remove_callback` is only ever called after a successful call to + // `probe_callback`, hence it's guaranteed that `ptr` points to a valid and initialized + // `KBox<T>` pointer created through `KBox::into_foreign`. + let _ = unsafe { KBox::<T>::from_foreign(ptr) }; + } +} + +impl<T: Driver + 'static> driver::Adapter for Adapter<T> { + type IdInfo = T::IdInfo; + + fn of_id_table() -> Option<of::IdTable<Self::IdInfo>> { + T::OF_ID_TABLE + } +} + +/// Declares a kernel module that exposes a single platform driver. +/// +/// # Examples +/// +/// ```ignore +/// kernel::module_platform_driver! { +/// type: MyDriver, +/// name: "Module name", +/// author: "Author name", +/// description: "Description", +/// license: "GPL v2", +/// } +/// ``` +#[macro_export] +macro_rules! module_platform_driver { + ($($f:tt)*) => { + $crate::module_driver!(<T>, $crate::platform::Adapter<T>, { $($f)* }); + }; +} + +/// The platform driver trait. +/// +/// Drivers must implement this trait in order to get a platform driver registered. +/// +/// # Example +/// +///``` +/// # use kernel::{bindings, c_str, of, platform}; +/// +/// struct MyDriver; +/// +/// kernel::of_device_table!( +/// OF_TABLE, +/// MODULE_OF_TABLE, +/// <MyDriver as platform::Driver>::IdInfo, +/// [ +/// (of::DeviceId::new(c_str!("test,device")), ()) +/// ] +/// ); +/// +/// impl platform::Driver for MyDriver { +/// type IdInfo = (); +/// const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE); +/// +/// fn probe( +/// _pdev: &mut platform::Device, +/// _id_info: Option<&Self::IdInfo>, +/// ) -> Result<Pin<KBox<Self>>> { +/// Err(ENODEV) +/// } +/// } +///``` +pub trait Driver { + /// The type holding driver private data about each device id supported by the driver. + /// + /// TODO: Use associated_type_defaults once stabilized: + /// + /// type IdInfo: 'static = (); + type IdInfo: 'static; + + /// The table of OF device ids supported by the driver. + const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>>; + + /// Platform driver probe. + /// + /// Called when a new platform device is added or discovered. + /// Implementers should attempt to initialize the device here. + fn probe(dev: &mut Device, id_info: Option<&Self::IdInfo>) -> Result<Pin<KBox<Self>>>; +} + +/// The platform device representation. +/// +/// A platform device is based on an always reference counted `device:Device` instance. Cloning a +/// platform device, hence, also increments the base device' reference count. +/// +/// # Invariants +/// +/// `Device` holds a valid reference of `ARef<device::Device>` whose underlying `struct device` is a +/// member of a `struct platform_device`. +#[derive(Clone)] +pub struct Device(ARef<device::Device>); + +impl Device { + /// Convert a raw kernel device into a `Device` + /// + /// # Safety + /// + /// `dev` must be an `Aref<device::Device>` whose underlying `bindings::device` is a member of a + /// `bindings::platform_device`. + unsafe fn from_dev(dev: ARef<device::Device>) -> Self { + Self(dev) + } + + fn as_raw(&self) -> *mut bindings::platform_device { + // SAFETY: By the type invariant `self.0.as_raw` is a pointer to the `struct device` + // embedded in `struct platform_device`. + unsafe { container_of!(self.0.as_raw(), bindings::platform_device, dev) }.cast_mut() + } +} + +impl AsRef<device::Device> for Device { + fn as_ref(&self) -> &device::Device { + &self.0 + } +} |