Re: [PATCH 4/6] rust: binder: enable `clippy::ref_as_ptr` lint

[Tamir Duberstein]

On Tue, May 26, 2026 at 8:46 AM Alice Ryhl <aliceryhl@xxxxxxxxxx> wrote:
>
> On Fri, May 22, 2026 at 07:12:49PM +0200, Tamir Duberstein wrote:
> > In Rust 1.78.0, Clippy introduced the `ref_as_ptr` lint [1]:
> >
> > > Using `as` casts may result in silently changing mutability or type.
> >
> > While this does not eliminate unchecked `as` conversions, it makes such
> > conversions easier to scrutinize. It also has the slight benefit of
> > removing a degree of freedom on which to bikeshed. Thus apply the changes
> > and enable the lint in the Binder Rust driver -- no functional change
> > intended.
> >
> > Link: https://rust-lang.github.io/rust-clippy/master/index.html#ref_as_ptr [1]
> > Signed-off-by: Tamir Duberstein <tamird@xxxxxxxxxx>
> > ---
> >  drivers/android/binder/node.rs             | 2 +-
> >  drivers/android/binder/page_range.rs       | 4 ++--
> >  drivers/android/binder/rust_binder_main.rs | 2 +-
> >  drivers/android/binder/trace.rs            | 2 +-
> >  4 files changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/android/binder/node.rs b/drivers/android/binder/node.rs
> > index d710940c3c8f..a4a3ddda6ac9 100644
> > --- a/drivers/android/binder/node.rs
> > +++ b/drivers/android/binder/node.rs
> > @@ -321,7 +321,7 @@ pub(crate) unsafe fn remove_node_info(
> >      /// An id that is unique across all binder nodes on the system. Used as the key in the
> >      /// `by_node` map.
> >      pub(crate) fn global_id(&self) -> usize {
> > -        (self as *const Node).addr()
> > +        core::ptr::from_ref(self).addr()
>
> Can we please import core::ptr?

Of course, will do.

> >      }
> >
> >      pub(crate) fn get_id(&self) -> (u64, u64) {
> > diff --git a/drivers/android/binder/page_range.rs b/drivers/android/binder/page_range.rs
> > index 927b0802e80d..93e79c08b89a 100644
> > --- a/drivers/android/binder/page_range.rs
> > +++ b/drivers/android/binder/page_range.rs
> > @@ -312,7 +312,7 @@ pub(crate) fn register_with_vma(&self, vma: &virt::VmaNew) -> Result<usize> {
> >
> >          // SAFETY: This just initializes the pages array.
> >          unsafe {
> > -            let self_ptr = self as *const ShrinkablePageRange;
> > +            let self_ptr = core::ptr::from_ref(self);
> >              for i in 0..num_pages {
> >                  let info = pages.as_mut_ptr().add(i);
> >                  (&raw mut (*info).range).write(self_ptr);
> > @@ -593,7 +593,7 @@ pub(crate) unsafe fn write<T: ?Sized>(&self, offset: usize, obj: &T) -> Result {
> >          unsafe {
> >              self.iterate(offset, size_of_val(obj), |page, offset, to_copy| {
> >                  // SAFETY: The sum of `offset` and `to_copy` is bounded by the size of T.
> > -                let obj_ptr = (obj as *const T).cast::<u8>().add(obj_offset);
> > +                let obj_ptr = core::ptr::from_ref(obj).cast::<u8>().add(obj_offset);
> >                  // SAFETY: We have a reference to the object, so the pointer is valid.
> >                  page.write_raw(obj_ptr, offset, to_copy)?;
> >                  obj_offset += to_copy;
> > diff --git a/drivers/android/binder/rust_binder_main.rs b/drivers/android/binder/rust_binder_main.rs
> > index fa28697982d3..88da29413e16 100644
> > --- a/drivers/android/binder/rust_binder_main.rs
> > +++ b/drivers/android/binder/rust_binder_main.rs
> > @@ -6,7 +6,7 @@
> >
> >  #![crate_name = "rust_binder"]
> >  #![recursion_limit = "256"]
> > -#![allow(clippy::as_underscore, clippy::ref_as_ptr, clippy::cast_lossless)]
> > +#![allow(clippy::as_underscore, clippy::cast_lossless)]
> >
> >  use kernel::{
> >      bindings::{self, seq_file},
> > diff --git a/drivers/android/binder/trace.rs b/drivers/android/binder/trace.rs
> > index 5539672d7285..b6cae57801fc 100644
> > --- a/drivers/android/binder/trace.rs
> > +++ b/drivers/android/binder/trace.rs
> > @@ -26,7 +26,7 @@
> >
> >  #[inline]
> >  fn raw_transaction(t: &Transaction) -> rust_binder_transaction {
> > -    t as *const Transaction as rust_binder_transaction
> > +    core::ptr::from_ref(t).cast_mut().cast()
>
> This just removes the type annotations I had. I'm not sure it's
> cleaner.

Would you prefer to locally disable the lint? Personally I don't find
the prior type mentions helpful: the pointer type is just the coerced
reference and the final type is the function return type, so all the
information is still plainly in view, but I don't feel strongly enough
to die on this hill; I would just like to remove the top-level lint
disablement.