[PATCH 3/6] rust: binder: enable `clippy::ptr_as_ptr` lint

[Tamir Duberstein]

In Rust 1.51.0, Clippy introduced the `ptr_as_ptr` lint [1]:

> Though `as` casts between raw pointers are not terrible,
> `pointer::cast` is safer because it cannot accidentally change pointer
> mutability or cast the pointer to other types like `usize`.

Apply the required 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#ptr_as_ptr [1]
Signed-off-by: Tamir Duberstein <tamird@xxxxxxxxxx>
---
 drivers/android/binder/page_range.rs       | 6 +++---
 drivers/android/binder/rust_binder_main.rs | 7 +------
 2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/android/binder/page_range.rs b/drivers/android/binder/page_range.rs
index e54a90e62402..927b0802e80d 100644
--- a/drivers/android/binder/page_range.rs
+++ b/drivers/android/binder/page_range.rs
@@ -571,7 +571,7 @@ pub(crate) unsafe fn read<T: FromBytes>(&self, offset: usize) -> Result<T> {
         unsafe {
             self.iterate(offset, size_of::<T>(), |page, offset, to_copy| {
                 // SAFETY: The sum of `offset` and `to_copy` is bounded by the size of T.
-                let obj_ptr = (out.as_mut_ptr() as *mut u8).add(out_offset);
+                let obj_ptr = out.as_mut_ptr().cast::<u8>().add(out_offset);
                 // SAFETY: The pointer points is in-bounds of the `out` variable, so it is valid.
                 page.read_raw(obj_ptr, offset, to_copy)?;
                 out_offset += to_copy;
@@ -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 as *const u8).add(obj_offset);
+                let obj_ptr = (obj as *const T).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;
@@ -712,7 +712,7 @@ fn drop(self: Pin<&mut Self>) {
 
     {
         // CAST: The `list_head` field is first in `PageInfo`.
-        let info = item as *mut PageInfo;
+        let info = item.cast::<PageInfo>();
         // SAFETY: The `range` field of `PageInfo` is immutable.
         range_ptr = unsafe { (*info).range };
         // SAFETY: The `range` outlives its `PageInfo` values.
diff --git a/drivers/android/binder/rust_binder_main.rs b/drivers/android/binder/rust_binder_main.rs
index d487638266e3..fa28697982d3 100644
--- a/drivers/android/binder/rust_binder_main.rs
+++ b/drivers/android/binder/rust_binder_main.rs
@@ -6,12 +6,7 @@
 
 #![crate_name = "rust_binder"]
 #![recursion_limit = "256"]
-#![allow(
-    clippy::as_underscore,
-    clippy::ref_as_ptr,
-    clippy::ptr_as_ptr,
-    clippy::cast_lossless
-)]
+#![allow(clippy::as_underscore, clippy::ref_as_ptr, clippy::cast_lossless)]
 
 use kernel::{
     bindings::{self, seq_file},

-- 
2.54.0