1. Patchew
  2. linux
  3. [PATCH 0/4] Implement TryFrom<&Device> for bus specific devices
  4. View patch

[PATCH 1/4] rust: device: implement Device::parent()

Danilo Krummrich posted 4 patches 9 months ago
There is a newer version of this series
[PATCH 1/4] rust: device: implement Device::parent()
Posted by Danilo Krummrich 9 months ago 
Device::parent() returns a reference to the device' parent device, if
any.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/device.rs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index 21b343a1dc4d..76b341441f3f 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -65,6 +65,19 @@ pub(crate) fn as_raw(&self) -> *mut bindings::device {
         self.0.get()
     }
 
+    /// Returns a reference to the parent device, if any.
+    pub fn parent<'a>(&self) -> Option<&'a Self> {
+        // SAFETY: By the type invariant `self.as_raw()` is always valid.
+        let parent = unsafe { *self.as_raw() }.parent;
+
+        if parent.is_null() {
+            None
+        } else {
+            // SAFETY: Since `parent` is not NULL, it must be a valid pointer to a `struct device`.
+            Some(unsafe { Self::as_ref(parent) })
+        }
+    }
+
     /// Convert a raw C `struct device` pointer to a `&'a Device`.
     ///
     /// # Safety
-- 
2.48.1
Re: [PATCH 1/4] rust: device: implement Device::parent()
Posted by Alice Ryhl 9 months ago 
On Wed, Mar 19, 2025 at 09:30:25PM +0100, Danilo Krummrich wrote:
> Device::parent() returns a reference to the device' parent device, if
> any.
> 
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  rust/kernel/device.rs | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
> index 21b343a1dc4d..76b341441f3f 100644
> --- a/rust/kernel/device.rs
> +++ b/rust/kernel/device.rs
> @@ -65,6 +65,19 @@ pub(crate) fn as_raw(&self) -> *mut bindings::device {
>          self.0.get()
>      }
>  
> +    /// Returns a reference to the parent device, if any.
> +    pub fn parent<'a>(&self) -> Option<&'a Self> {
> +        // SAFETY: By the type invariant `self.as_raw()` is always valid.
> +        let parent = unsafe { *self.as_raw() }.parent;

This means:
1. Copy the entire `struct device` onto the stack.
2. Read the `parent` field of the copy.

Please write this instead to only read the `parent` field:
let parent = unsafe { *self.as_raw().parent };

> +        if parent.is_null() {
> +            None
> +        } else {
> +            // SAFETY: Since `parent` is not NULL, it must be a valid pointer to a `struct device`.
> +            Some(unsafe { Self::as_ref(parent) })
> +        }
> +    }
> +
>      /// Convert a raw C `struct device` pointer to a `&'a Device`.
>      ///
>      /// # Safety
> -- 
> 2.48.1
>
Re: [PATCH 1/4] rust: device: implement Device::parent()
Posted by Alice Ryhl 9 months ago 
On Thu, Mar 20, 2025 at 9:34 AM Alice Ryhl <aliceryhl@google.com> wrote:
>
> On Wed, Mar 19, 2025 at 09:30:25PM +0100, Danilo Krummrich wrote:
> > Device::parent() returns a reference to the device' parent device, if
> > any.
> >
> > Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> > ---
> >  rust/kernel/device.rs | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> >
> > diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
> > index 21b343a1dc4d..76b341441f3f 100644
> > --- a/rust/kernel/device.rs
> > +++ b/rust/kernel/device.rs
> > @@ -65,6 +65,19 @@ pub(crate) fn as_raw(&self) -> *mut bindings::device {
> >          self.0.get()
> >      }
> >
> > +    /// Returns a reference to the parent device, if any.
> > +    pub fn parent<'a>(&self) -> Option<&'a Self> {
> > +        // SAFETY: By the type invariant `self.as_raw()` is always valid.
> > +        let parent = unsafe { *self.as_raw() }.parent;
>
> This means:
> 1. Copy the entire `struct device` onto the stack.
> 2. Read the `parent` field of the copy.
>
> Please write this instead to only read the `parent` field:
> let parent = unsafe { *self.as_raw().parent };

Sorry I meant (*self.as_raw()).parent
Re: [PATCH 1/4] rust: device: implement Device::parent()
Posted by Danilo Krummrich 9 months ago 
On Thu, Mar 20, 2025 at 09:40:45AM +0100, Alice Ryhl wrote:
> On Thu, Mar 20, 2025 at 9:34 AM Alice Ryhl <aliceryhl@google.com> wrote:
> >
> > On Wed, Mar 19, 2025 at 09:30:25PM +0100, Danilo Krummrich wrote:
> > > Device::parent() returns a reference to the device' parent device, if
> > > any.
> > >
> > > Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> > > ---
> > >  rust/kernel/device.rs | 13 +++++++++++++
> > >  1 file changed, 13 insertions(+)
> > >
> > > diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
> > > index 21b343a1dc4d..76b341441f3f 100644
> > > --- a/rust/kernel/device.rs
> > > +++ b/rust/kernel/device.rs
> > > @@ -65,6 +65,19 @@ pub(crate) fn as_raw(&self) -> *mut bindings::device {
> > >          self.0.get()
> > >      }
> > >
> > > +    /// Returns a reference to the parent device, if any.
> > > +    pub fn parent<'a>(&self) -> Option<&'a Self> {
> > > +        // SAFETY: By the type invariant `self.as_raw()` is always valid.
> > > +        let parent = unsafe { *self.as_raw() }.parent;
> >
> > This means:
> > 1. Copy the entire `struct device` onto the stack.
> > 2. Read the `parent` field of the copy.
> >
> > Please write this instead to only read the `parent` field:
> > let parent = unsafe { *self.as_raw().parent };
> 
> Sorry I meant (*self.as_raw()).parent

Good catch, thanks!
Re: [PATCH 1/4] rust: device: implement Device::parent()
Posted by Alice Ryhl 9 months ago 
On Thu, Mar 20, 2025 at 01:19:11PM +0100, Danilo Krummrich wrote:
> On Thu, Mar 20, 2025 at 09:40:45AM +0100, Alice Ryhl wrote:
> > On Thu, Mar 20, 2025 at 9:34 AM Alice Ryhl <aliceryhl@google.com> wrote:
> > >
> > > On Wed, Mar 19, 2025 at 09:30:25PM +0100, Danilo Krummrich wrote:
> > > > Device::parent() returns a reference to the device' parent device, if
> > > > any.
> > > >
> > > > Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> > > > ---
> > > >  rust/kernel/device.rs | 13 +++++++++++++
> > > >  1 file changed, 13 insertions(+)
> > > >
> > > > diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
> > > > index 21b343a1dc4d..76b341441f3f 100644
> > > > --- a/rust/kernel/device.rs
> > > > +++ b/rust/kernel/device.rs
> > > > @@ -65,6 +65,19 @@ pub(crate) fn as_raw(&self) -> *mut bindings::device {
> > > >          self.0.get()
> > > >      }
> > > >
> > > > +    /// Returns a reference to the parent device, if any.
> > > > +    pub fn parent<'a>(&self) -> Option<&'a Self> {
> > > > +        // SAFETY: By the type invariant `self.as_raw()` is always valid.
> > > > +        let parent = unsafe { *self.as_raw() }.parent;
> > >
> > > This means:
> > > 1. Copy the entire `struct device` onto the stack.
> > > 2. Read the `parent` field of the copy.
> > >
> > > Please write this instead to only read the `parent` field:
> > > let parent = unsafe { *self.as_raw().parent };
> > 
> > Sorry I meant (*self.as_raw()).parent
> 
> Good catch, thanks! 

With that fixed you may add
Reviewed-by: Alice Ryhl <aliceryhl@google.com>

Patchew 2.1-devel-b67e4c2

© 2016 - 2025 Red Hat, Inc.