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2f5606afa4
The prefix as_* should not be used for a constructor. Constructors usually use the prefix from_* instead. Some prior art in the stdlib: Box::from_raw, CString::from_raw, Rc::from_raw, Arc::from_raw, Waker::from_raw, File::from_raw_fd. There is also prior art in the kernel crate: cpufreq::Policy::from_raw, fs::File::from_raw_file, Kuid::from_raw, ARef::from_raw, SeqFile::from_raw, VmaNew::from_raw, Io::from_raw. Link: https://lore.kernel.org/r/aCd8D5IA0RXZvtcv@pollux Signed-off-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Benno Lossin <lossin@kernel.org> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Link: https://lore.kernel.org/r/20250711-device-as-ref-v2-1-1b16ab6402d7@google.com Signed-off-by: Danilo Krummrich <dakr@kernel.org>
77 lines
3 KiB
Rust
77 lines
3 KiB
Rust
// SPDX-License-Identifier: GPL-2.0-only
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//! Abstractions for the faux bus.
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//!
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//! This module provides bindings for working with faux devices in kernel modules.
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//!
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//! C header: [`include/linux/device/faux.h`]
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use crate::{bindings, device, error::code::*, prelude::*};
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use core::ptr::{addr_of_mut, null, null_mut, NonNull};
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/// The registration of a faux device.
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///
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/// This type represents the registration of a [`struct faux_device`]. When an instance of this type
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/// is dropped, its respective faux device will be unregistered from the system.
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///
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/// # Invariants
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///
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/// `self.0` always holds a valid pointer to an initialized and registered [`struct faux_device`].
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///
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/// [`struct faux_device`]: srctree/include/linux/device/faux.h
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pub struct Registration(NonNull<bindings::faux_device>);
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impl Registration {
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/// Create and register a new faux device with the given name.
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#[inline]
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pub fn new(name: &CStr, parent: Option<&device::Device>) -> Result<Self> {
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// SAFETY:
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// - `name` is copied by this function into its own storage
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// - `faux_ops` is safe to leave NULL according to the C API
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// - `parent` can be either NULL or a pointer to a `struct device`, and `faux_device_create`
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// will take a reference to `parent` using `device_add` - ensuring that it remains valid
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// for the lifetime of the faux device.
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let dev = unsafe {
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bindings::faux_device_create(
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name.as_char_ptr(),
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parent.map_or(null_mut(), |p| p.as_raw()),
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null(),
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)
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};
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// The above function will return either a valid device, or NULL on failure
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// INVARIANT: The device will remain registered until faux_device_destroy() is called, which
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// happens in our Drop implementation.
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Ok(Self(NonNull::new(dev).ok_or(ENODEV)?))
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}
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fn as_raw(&self) -> *mut bindings::faux_device {
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self.0.as_ptr()
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}
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}
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impl AsRef<device::Device> for Registration {
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fn as_ref(&self) -> &device::Device {
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// SAFETY: The underlying `device` in `faux_device` is guaranteed by the C API to be
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// a valid initialized `device`.
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unsafe { device::Device::from_raw(addr_of_mut!((*self.as_raw()).dev)) }
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}
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}
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impl Drop for Registration {
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#[inline]
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fn drop(&mut self) {
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// SAFETY: `self.0` is a valid registered faux_device via our type invariants.
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unsafe { bindings::faux_device_destroy(self.as_raw()) }
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}
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}
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// SAFETY: The faux device API is thread-safe as guaranteed by the device core, as long as
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// faux_device_destroy() is guaranteed to only be called once - which is guaranteed by our type not
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// having Copy/Clone.
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unsafe impl Send for Registration {}
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// SAFETY: The faux device API is thread-safe as guaranteed by the device core, as long as
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// faux_device_destroy() is guaranteed to only be called once - which is guaranteed by our type not
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// having Copy/Clone.
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unsafe impl Sync for Registration {}
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