[PATCH] rust: io: convert ResourceSize to newtype

[PATCH] rust: io: convert ResourceSize to newtype

[Moritz Zielke via B4 Relay]

From: Moritz Zielke <moritz.zielke@gmail.com>

Makes ResourceSize a newtype wrapper around the type for which it
previously was an alias. This should help prevent mistakes by
restricting what operations are possible with ResourceSize.

Suggested-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://github.com/Rust-for-Linux/linux/issues/1203
Signed-off-by: Moritz Zielke <moritz.zielke@gmail.com>
---
I think with [1] the prerequisites for making ResourceSize a newtype
have been applied to the driver-core-testing branch of driver-core.
So I developed this patch against driver-core-testing. 

[1] https://lore.kernel.org/lkml/DE0C1KA14PDQ.Q2CJDDTQPWOK@kernel.org/
---
 rust/kernel/io.rs          | 38 ++++++++++++++++++++++++++++++++++++--
 rust/kernel/io/resource.rs |  6 +++---
 2 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index 98e8b84e68d1..490f60680090 100644
--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -4,6 +4,8 @@
 //!
 //! C header: [`include/asm-generic/io.h`](srctree/include/asm-generic/io.h)
 
+use core::num::TryFromIntError;
+
 use crate::{
     bindings,
     prelude::*, //
@@ -23,9 +25,41 @@
 
 /// Resource Size type.
 ///
-/// This is a type alias to either `u32` or `u64` depending on the config option
+/// This is a transparent wrapper around either `u32` or `u64` depending on the config option
 /// `CONFIG_PHYS_ADDR_T_64BIT`, and it can be a u64 even on 32-bit architectures.
-pub type ResourceSize = bindings::resource_size_t;
+#[repr(transparent)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Default)]
+pub struct ResourceSize(bindings::phys_addr_t);
+
+impl From<ffi::c_uint> for ResourceSize {
+    #[inline]
+    fn from(value: ffi::c_uint) -> Self {
+        Self(value.into())
+    }
+}
+
+impl From<bindings::resource_size_t> for ResourceSize {
+    #[inline]
+    fn from(value: bindings::resource_size_t) -> Self {
+        Self(value.into())
+    }
+}
+
+impl TryFrom<ResourceSize> for usize {
+    type Error = TryFromIntError;
+
+    #[inline]
+    fn try_from(value: ResourceSize) -> Result<Self, Self::Error> {
+        usize::try_from(value.0)
+    }
+}
+
+impl From<ResourceSize> for bindings::resource_size_t {
+    #[inline]
+    fn from(value: ResourceSize) -> Self {
+        value.0
+    }
+}
 
 /// Raw representation of an MMIO region.
 ///
diff --git a/rust/kernel/io/resource.rs b/rust/kernel/io/resource.rs
index 56cfde97ce87..841bb00b8418 100644
--- a/rust/kernel/io/resource.rs
+++ b/rust/kernel/io/resource.rs
@@ -58,7 +58,7 @@ fn drop(&mut self) {
         };
 
         // SAFETY: Safe as per the invariant of `Region`.
-        unsafe { release_fn(start, size) };
+        unsafe { release_fn(start, size.into()) };
     }
 }
 
@@ -114,7 +114,7 @@ pub fn request_region(
             bindings::__request_region(
                 self.0.get(),
                 start,
-                size,
+                size.into(),
                 name.as_char_ptr(),
                 flags.0 as c_int,
             )
@@ -130,7 +130,7 @@ pub fn request_region(
     pub fn size(&self) -> ResourceSize {
         let inner = self.0.get();
         // SAFETY: Safe as per the invariants of `Resource`.
-        unsafe { bindings::resource_size(inner) }
+        unsafe { bindings::resource_size(inner) }.into()
     }
 
     /// Returns the start address of the resource.

---
base-commit: 473b9f331718267815649cd93801da832200db71
change-id: 20251203-res-size-newtype-6fe140bc0038

Best regards,
-- 
Moritz Zielke <moritz.zielke@gmail.com>

Re: [PATCH] rust: io: convert ResourceSize to newtype

[kernel test robot]

Hi Moritz,

kernel test robot noticed the following build errors:

[auto build test ERROR on 473b9f331718267815649cd93801da832200db71]

url:    https://github.com/intel-lab-lkp/linux/commits/Moritz-Zielke-via-B4-Relay/rust-io-convert-ResourceSize-to-newtype/20251204-012104
base:   473b9f331718267815649cd93801da832200db71
patch link:    https://lore.kernel.org/r/20251203-res-size-newtype-v1-1-22ed0b8a7a18%40gmail.com
patch subject: [PATCH] rust: io: convert ResourceSize to newtype
config: um-randconfig-r064-20251207 (https://download.01.org/0day-ci/archive/20251209/202512090237.rE4zx0Ob-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project a805147ac1ba123916de182babb0831fbb148756)
rustc: rustc 1.88.0 (6b00bc388 2025-06-23)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251209/202512090237.rE4zx0Ob-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202512090237.rE4zx0Ob-lkp@intel.com/

All errors (new ones prefixed by >>):

>> error[E0605]: non-primitive cast: `ResourceSize` as `usize`
   --> drivers/gpu/nova-core/firmware/gsp.rs:234:25
   |
   234 |         let num_pages = (sg_entry.dma_len() as usize).div_ceil(GSP_PAGE_SIZE);
   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ an `as` expression can only be used to convert between primitive types or to coerce to a specific trait object

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki