On 10/2/25 1:41 AM, Alexandre Courbot wrote:
On Tue Sep 30, 2025 at 11:45 PM JST, Joel Fernandes wrote:
Add KUNIT tests to make sure the macro is working correctly.
Signed-off-by: Joel Fernandes <joelagn...@nvidia.com>
---
rust/kernel/bitfield.rs | 321 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 321 insertions(+)
diff --git a/rust/kernel/bitfield.rs b/rust/kernel/bitfield.rs
index fed19918c3b9..9a20bcd2eb60 100644
--- a/rust/kernel/bitfield.rs
+++ b/rust/kernel/bitfield.rs
@@ -402,3 +402,324 @@ fn default() -> Self {
}
};
}
+
+#[::kernel::macros::kunit_tests(kernel_bitfield)]
+mod tests {
+ use core::convert::TryFrom;
+
+ // Enum types for testing => and ?=> conversions
+ #[derive(Debug, Clone, Copy, PartialEq)]
+ enum MemoryType {
+ Unmapped = 0,
+ Normal = 1,
+ Device = 2,
+ Reserved = 3,
+ }
+
+ impl Default for MemoryType {
+ fn default() -> Self {
+ MemoryType::Unmapped
+ }
+ }
Tip: you can add `Default` to the `#[derive]` marker of `MemoryType` and
mark the variant you want as default with `#[default]` instead of
providing a full impl block:
#[derive(Debug, Default, Clone, Copy, PartialEq)]
enum MemoryType {
#[default]
Unmapped = 0,
Normal = 1,
Device = 2,
Reserved = 3,
}
I would alternatively recommend to provide a `MemoryType::new` impl with
a `const` definition:
```rust
impl MemoryType {
pub const fn new() -> Self {
Self::Unmapped
}
}
impl Default for MemoryType {
fn default() -> Self {
Self::new()
}
}
```
This pattern allows using `MemoryType::new()` in `const` contexts, while
also providing the `Default` impl using the same default. It's somewhat
of a workaround until we get `const` traits.
+
+ impl TryFrom<u8> for MemoryType {
+ type Error = u8;
+ fn try_from(value: u8) -> Result<Self, Self::Error> {
+ match value {
+ 0 => Ok(MemoryType::Unmapped),
+ 1 => Ok(MemoryType::Normal),
+ 2 => Ok(MemoryType::Device),
+ 3 => Ok(MemoryType::Reserved),
+ _ => Err(value),
+ }
+ }
+ }
+
+ impl From<MemoryType> for u64 {
+ fn from(mt: MemoryType) -> u64 {
+ mt as u64
+ }
+ }
+
+ #[derive(Debug, Clone, Copy, PartialEq)]
+ enum Priority {
+ Low = 0,
+ Medium = 1,
+ High = 2,
+ Critical = 3,
+ }
+
+ impl Default for Priority {
+ fn default() -> Self {
+ Priority::Low
+ }
+ }
+
+ impl From<u8> for Priority {
+ fn from(value: u8) -> Self {
+ match value & 0x3 {
+ 0 => Priority::Low,
+ 1 => Priority::Medium,
+ 2 => Priority::High,
+ _ => Priority::Critical,
+ }
+ }
+ }
+
+ impl From<Priority> for u16 {
+ fn from(p: Priority) -> u16 {
+ p as u16
+ }
+ }
+
+ bitfield! {
+ struct TestPageTableEntry(u64) {
+ 0:0 present as bool;
+ 1:1 writable as bool;
+ 11:9 available as u8;
+ 13:12 mem_type as u8 ?=> MemoryType;
+ 17:14 extended_type as u8 ?=> MemoryType; // For testing
failures
+ 51:12 pfn as u64;
+ 51:12 pfn_overlap as u64;
+ 61:52 available2 as u16;
+ }
+ }
+
+ bitfield! {
+ struct TestControlRegister(u16) {
+ 0:0 enable as bool;
+ 3:1 mode as u8;
+ 5:4 priority as u8 => Priority;
+ 7:4 priority_nibble as u8;
+ 15:8 channel as u8;
+ }
+ }
+
+ bitfield! {
+ struct TestStatusRegister(u8) {
+ 0:0 ready as bool;
+ 1:1 error as bool;
+ 3:2 state as u8;
+ 7:4 reserved as u8;
+ 7:0 full_byte as u8; // For entire register
+ }
+ }
+
+ #[test]
+ fn test_single_bits() {
+ let mut pte = TestPageTableEntry::default();
+
+ assert!(!pte.present());
+ assert!(!pte.writable());
+
+ pte = pte.set_present(true);
+ assert!(pte.present());
+
+ pte = pte.set_writable(true);
+ assert!(pte.writable());
+
+ pte = pte.set_writable(false);
+ assert!(!pte.writable());
+
+ assert_eq!(pte.available(), 0);
+ pte = pte.set_available(0x5);
+ assert_eq!(pte.available(), 0x5);
I'd suggest testing the actual raw value of the register on top of
invoking the getter. That way you also test that:
- The right field is actually written (i.e. if the offset is off by one,
the getter will return the expected result even though the bitfield
has the wrong value),
- No other field has been affected.
So something like:
pte = pte.set_present(true);
assert!(pte.present());
assert(pte.into(), 0x1u64);
pte = pte.set_writable(true);
assert!(pte.writable());
assert(pte.into(), 0x3u64);
It might look a bit gross, but it is ok since these are not doctests
that users are going to take as a reference, so we case improve test
coverage at the detriment of readability.
