Implement the `auxiliary::Registration` type, which provides an API to
create and register new auxiliary devices in the system.
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
rust/kernel/auxiliary.rs | 80 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 79 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
index e453f821f7cb..fc4bb5388a9b 100644
--- a/rust/kernel/auxiliary.rs
+++ b/rust/kernel/auxiliary.rs
@@ -5,7 +5,7 @@
//! C header: [`include/linux/auxiliary_bus.h`](srctree/include/linux/auxiliary_bus.h)
use crate::{
- bindings, device,
+ bindings, container_of, device,
device_id::RawDeviceId,
driver,
error::{to_result, Result},
@@ -219,6 +219,16 @@ pub fn id(&self) -> u32 {
// `struct auxiliary_device`.
unsafe { (*self.as_raw()).id }
}
+
+ extern "C" fn release(dev: *mut bindings::device) {
+ // SAFETY: By the type invariant `self.0.as_raw` is a pointer to the `struct device`
+ // embedded in `struct auxiliary_device`.
+ let adev = unsafe { container_of!(dev, bindings::auxiliary_device, dev) }.cast_mut();
+
+ // SAFETY: `adev` points to the memory that has been allocated in `Registration::new`, via
+ // `KBox::new(Opaque::<bindings::auxiliary_device>::zeroed(), GFP_KERNEL)`.
+ let _ = unsafe { KBox::<Opaque<bindings::auxiliary_device>>::from_raw(adev.cast()) };
+ }
}
impl Deref for Device<device::Core> {
@@ -265,3 +275,71 @@ fn as_ref(&self) -> &device::Device {
unsafe { device::Device::as_ref(dev) }
}
}
+
+/// The registration of an auxiliary device.
+///
+/// This type represents the registration of a [`struct auxiliary_device`]. When an instance of this
+/// type is dropped, its respective auxiliary device will be unregistered from the system.
+///
+/// # Invariants
+///
+/// `self.0` always holds a valid pointer to an initialized and registered
+/// [`struct auxiliary_device`].
+pub struct Registration(NonNull<bindings::auxiliary_device>);
+
+impl Registration {
+ /// Create and register a new auxiliary device.
+ pub fn new(parent: &device::Device, name: &CStr, id: u32, modname: &CStr) -> Result<Self> {
+ let boxed = KBox::new(Opaque::<bindings::auxiliary_device>::zeroed(), GFP_KERNEL)?;
+ let adev = boxed.get();
+
+ // SAFETY: It's safe to set the fields of `struct auxiliary_device` on initialization.
+ unsafe {
+ (*adev).dev.parent = parent.as_raw();
+ (*adev).dev.release = Some(Device::release);
+ (*adev).name = name.as_char_ptr();
+ (*adev).id = id;
+ }
+
+ // SAFETY: `adev` is guaranteed to be a valid pointer to a `struct auxiliary_device`,
+ // which has not been initialized yet.
+ unsafe { bindings::auxiliary_device_init(adev) };
+
+ // Now that `adev` is initialized, leak the `Box`; the corresponding memory will be freed
+ // by `Device::release` when the last reference to the `struct auxiliary_device` is dropped.
+ let _ = KBox::into_raw(boxed);
+
+ // SAFETY:
+ // - `adev` is guaranteed to be a valid pointer to a `struct auxiliary_device`, which has
+ // been initialialized,
+ // - `modname.as_char_ptr()` is a NULL terminated string.
+ let ret = unsafe { bindings::__auxiliary_device_add(adev, modname.as_char_ptr()) };
+ if ret != 0 {
+ // SAFETY: `adev` is guaranteed to be a valid pointer to a `struct auxiliary_device`,
+ // which has been initialialized.
+ unsafe { bindings::auxiliary_device_uninit(adev) };
+
+ return Err(Error::from_errno(ret));
+ }
+
+ // SAFETY: `adev` is guaranteed to be non-null, since the `KBox` was allocated successfully.
+ //
+ // INVARIANT: The device will remain registered until `auxiliary_device_delete()` is called,
+ // which happens in `Self::drop()`.
+ Ok(Self(unsafe { NonNull::new_unchecked(adev) }))
+ }
+}
+
+impl Drop for Registration {
+ fn drop(&mut self) {
+ // SAFETY: By the type invariant of `Self`, `self.0.as_ptr()` is a valid registered
+ // `struct auxiliary_device`.
+ unsafe { bindings::auxiliary_device_delete(self.0.as_ptr()) };
+
+ // This drops the reference we acquired through `auxiliary_device_init()`.
+ //
+ // SAFETY: By the type invariant of `Self`, `self.0.as_ptr()` is a valid registered
+ // `struct auxiliary_device`.
+ unsafe { bindings::auxiliary_device_uninit(self.0.as_ptr()) };
+ }
+}
--
2.48.1On Thu, 13 Mar 2025 03:23:52 +0100 Danilo Krummrich <dakr@kernel.org> wrote:
> Implement the `auxiliary::Registration` type, which provides an API to
> create and register new auxiliary devices in the system.
>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
> rust/kernel/auxiliary.rs | 80 +++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 79 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
> index e453f821f7cb..fc4bb5388a9b 100644
> --- a/rust/kernel/auxiliary.rs
> +++ b/rust/kernel/auxiliary.rs
> @@ -5,7 +5,7 @@
> //! C header: [`include/linux/auxiliary_bus.h`](srctree/include/linux/auxiliary_bus.h)
>
> use crate::{
> - bindings, device,
> + bindings, container_of, device,
> device_id::RawDeviceId,
> driver,
> error::{to_result, Result},
> @@ -219,6 +219,16 @@ pub fn id(&self) -> u32 {
> // `struct auxiliary_device`.
> unsafe { (*self.as_raw()).id }
> }
> +
> + extern "C" fn release(dev: *mut bindings::device) {
> + // SAFETY: By the type invariant `self.0.as_raw` is a pointer to the `struct device`
> + // embedded in `struct auxiliary_device`.
> + let adev = unsafe { container_of!(dev, bindings::auxiliary_device, dev) }.cast_mut();
> +
> + // SAFETY: `adev` points to the memory that has been allocated in `Registration::new`, via
> + // `KBox::new(Opaque::<bindings::auxiliary_device>::zeroed(), GFP_KERNEL)`.
> + let _ = unsafe { KBox::<Opaque<bindings::auxiliary_device>>::from_raw(adev.cast()) };
> + }
> }
>
> impl Deref for Device<device::Core> {
> @@ -265,3 +275,71 @@ fn as_ref(&self) -> &device::Device {
> unsafe { device::Device::as_ref(dev) }
> }
> }
> +
> +/// The registration of an auxiliary device.
> +///
> +/// This type represents the registration of a [`struct auxiliary_device`]. When an instance of this
> +/// type is dropped, its respective auxiliary device will be unregistered from the system.
> +///
> +/// # Invariants
> +///
> +/// `self.0` always holds a valid pointer to an initialized and registered
> +/// [`struct auxiliary_device`].
> +pub struct Registration(NonNull<bindings::auxiliary_device>);
> +
> +impl Registration {
> + /// Create and register a new auxiliary device.
> + pub fn new(parent: &device::Device, name: &CStr, id: u32, modname: &CStr) -> Result<Self> {
> + let boxed = KBox::new(Opaque::<bindings::auxiliary_device>::zeroed(), GFP_KERNEL)?;
You can use `KBox::init(kernel::init::zeroed(), GFP_KERNEL)` here. It avoids
the need for the first patch.
> + let adev = boxed.get();
> +
> + // SAFETY: It's safe to set the fields of `struct auxiliary_device` on initialization.
> + unsafe {
> + (*adev).dev.parent = parent.as_raw();
> + (*adev).dev.release = Some(Device::release);
> + (*adev).name = name.as_char_ptr();
> + (*adev).id = id;
> + }
> +
> + // SAFETY: `adev` is guaranteed to be a valid pointer to a `struct auxiliary_device`,
> + // which has not been initialized yet.
> + unsafe { bindings::auxiliary_device_init(adev) };
> +
> + // Now that `adev` is initialized, leak the `Box`; the corresponding memory will be freed
> + // by `Device::release` when the last reference to the `struct auxiliary_device` is dropped.
> + let _ = KBox::into_raw(boxed);
> +
> + // SAFETY:
> + // - `adev` is guaranteed to be a valid pointer to a `struct auxiliary_device`, which has
> + // been initialialized,
> + // - `modname.as_char_ptr()` is a NULL terminated string.
> + let ret = unsafe { bindings::__auxiliary_device_add(adev, modname.as_char_ptr()) };
> + if ret != 0 {
> + // SAFETY: `adev` is guaranteed to be a valid pointer to a `struct auxiliary_device`,
> + // which has been initialialized.
> + unsafe { bindings::auxiliary_device_uninit(adev) };
> +
> + return Err(Error::from_errno(ret));
> + }
> +
> + // SAFETY: `adev` is guaranteed to be non-null, since the `KBox` was allocated successfully.
> + //
> + // INVARIANT: The device will remain registered until `auxiliary_device_delete()` is called,
> + // which happens in `Self::drop()`.
> + Ok(Self(unsafe { NonNull::new_unchecked(adev) }))
> + }
> +}
> +
> +impl Drop for Registration {
> + fn drop(&mut self) {
> + // SAFETY: By the type invariant of `Self`, `self.0.as_ptr()` is a valid registered
> + // `struct auxiliary_device`.
> + unsafe { bindings::auxiliary_device_delete(self.0.as_ptr()) };
> +
> + // This drops the reference we acquired through `auxiliary_device_init()`.
> + //
> + // SAFETY: By the type invariant of `Self`, `self.0.as_ptr()` is a valid registered
> + // `struct auxiliary_device`.
> + unsafe { bindings::auxiliary_device_uninit(self.0.as_ptr()) };
> + }
> +}
> --
> 2.48.1
>
>
Benoît du Garreau
On Mon Mar 17, 2025 at 9:42 PM CET, Benoît du Garreau wrote:
> On Thu, 13 Mar 2025 03:23:52 +0100 Danilo Krummrich <dakr@kernel.org> wrote:
>> Implement the `auxiliary::Registration` type, which provides an API to
>> +impl Registration {
>> + /// Create and register a new auxiliary device.
>> + pub fn new(parent: &device::Device, name: &CStr, id: u32, modname: &CStr) -> Result<Self> {
>> + let boxed = KBox::new(Opaque::<bindings::auxiliary_device>::zeroed(), GFP_KERNEL)?;
>
> You can use `KBox::init(kernel::init::zeroed(), GFP_KERNEL)` here. It avoids
> the need for the first patch.
We probably should have the zeroed function on the `Zeroable` trait...
---
Cheers,
Benno
On Mon, Mar 17, 2025 at 09:42:51PM +0100, Benoît du Garreau wrote:
> On Thu, 13 Mar 2025 03:23:52 +0100 Danilo Krummrich <dakr@kernel.org> wrote:
>
> > +impl Registration {
> > + /// Create and register a new auxiliary device.
> > + pub fn new(parent: &device::Device, name: &CStr, id: u32, modname: &CStr) -> Result<Self> {
> > + let boxed = KBox::new(Opaque::<bindings::auxiliary_device>::zeroed(), GFP_KERNEL)?;
>
> You can use `KBox::init(kernel::init::zeroed(), GFP_KERNEL)` here. It avoids
> the need for the first patch.
You're right, that works indeed, the full call looks like this.
let boxed = KBox::init(kernel::init::zeroed::<Opaque::<bindings::auxiliary_device>>(), GFP_KERNEL)?;
However, I think Opaque::zeroed() reads a bit better. Unless anything speaks
against adding it, I think I prefer it as it is.
© 2016 - 2025 Red Hat, Inc.