[PATCH v2 2/3] rust: bitfield: Add KUNIT tests for bitfield

[Alexandre Courbot <acourbot@nvidia.com>]

From: Joel Fernandes <joelagnelf@nvidia.com>

Add KUNIT tests to make sure the macro is working correctly.

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
[acourbot: update code to latest bitfield! macro.]
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
 rust/kernel/bitfield.rs | 318 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 318 insertions(+)

diff --git a/rust/kernel/bitfield.rs b/rust/kernel/bitfield.rs
index f5948eec8a76..9ab8dafff36c 100644
--- a/rust/kernel/bitfield.rs
+++ b/rust/kernel/bitfield.rs
@@ -489,3 +489,321 @@ fn fmt(&self, f: &mut ::kernel::fmt::Formatter<'_>) -> ::kernel::fmt::Result {
         }
     };
 }
+
+#[::kernel::macros::kunit_tests(kernel_bitfield)]
+mod tests {
+    use core::convert::TryFrom;
+
+    use pin_init::Zeroable;
+
+    use kernel::num::Bounded;
+
+    // Enum types for testing => and ?=> conversions
+    #[derive(Debug, Clone, Copy, PartialEq)]
+    enum MemoryType {
+        Unmapped = 0,
+        Normal = 1,
+        Device = 2,
+        Reserved = 3,
+    }
+
+    impl TryFrom<Bounded<u64, 4>> for MemoryType {
+        type Error = u64;
+        fn try_from(value: Bounded<u64, 4>) -> Result<Self, Self::Error> {
+            match value.get() {
+                0 => Ok(MemoryType::Unmapped),
+                1 => Ok(MemoryType::Normal),
+                2 => Ok(MemoryType::Device),
+                3 => Ok(MemoryType::Reserved),
+                _ => Err(value.get()),
+            }
+        }
+    }
+
+    impl From<MemoryType> for Bounded<u64, 4> {
+        fn from(mt: MemoryType) -> Bounded<u64, 4> {
+            Bounded::from_expr(mt as u64)
+        }
+    }
+
+    #[derive(Debug, Clone, Copy, PartialEq)]
+    enum Priority {
+        Low = 0,
+        Medium = 1,
+        High = 2,
+        Critical = 3,
+    }
+
+    impl From<Bounded<u16, 2>> for Priority {
+        fn from(value: Bounded<u16, 2>) -> Self {
+            match value & 0x3 {
+                0 => Priority::Low,
+                1 => Priority::Medium,
+                2 => Priority::High,
+                _ => Priority::Critical,
+            }
+        }
+    }
+
+    impl From<Priority> for Bounded<u16, 2> {
+        fn from(p: Priority) -> Bounded<u16, 2> {
+            Bounded::from_expr(p as u16)
+        }
+    }
+
+    bitfield! {
+        struct TestPageTableEntry(u64) {
+            0:0       present;
+            1:1       writable;
+            11:9      available;
+            15:12     mem_type ?=> MemoryType;
+            51:16     pfn;
+            61:52     available2;
+        }
+    }
+
+    bitfield! {
+        struct TestControlRegister(u16) {
+            0:0       enable;
+            3:1       mode;
+            5:4       priority => Priority;
+            7:4       priority_nibble;
+            15:8      channel;
+        }
+    }
+
+    bitfield! {
+        struct TestStatusRegister(u8) {
+            0:0       ready;
+            1:1       error;
+            3:2       state;
+            7:4       reserved;
+            7:0       full_byte;  // For entire register
+        }
+    }
+
+    #[test]
+    fn test_single_bits() {
+        let mut pte = TestPageTableEntry::zeroed();
+
+        assert!(!pte.present().into_bool());
+        assert!(!pte.writable().into_bool());
+        assert_eq!(u64::from(pte), 0x0);
+
+        pte = pte.with_present(true);
+        assert!(pte.present().into_bool());
+        assert_eq!(u64::from(pte), 0x1);
+
+        pte = pte.with_writable(true);
+        assert!(pte.writable().into_bool());
+        assert_eq!(u64::from(pte), 0x3);
+
+        pte = pte.with_writable(false);
+        assert!(!pte.writable().into_bool());
+        assert_eq!(u64::from(pte), 0x1);
+
+        assert_eq!(pte.available(), 0);
+        pte = pte.with_const_available::<0x5>();
+        assert_eq!(pte.available(), 0x5);
+        assert_eq!(u64::from(pte), 0xA01);
+    }
+
+    #[test]
+    fn test_range_fields() {
+        let mut pte = TestPageTableEntry::zeroed();
+        assert_eq!(u64::from(pte), 0x0);
+
+        pte = pte.with_const_pfn::<0x123456>();
+        assert_eq!(pte.pfn(), 0x123456);
+        assert_eq!(u64::from(pte), 0x1234560000);
+
+        pte = pte.with_const_available::<0x7>();
+        assert_eq!(pte.available(), 0x7);
+        assert_eq!(u64::from(pte), 0x1234560E00);
+
+        pte = pte.with_const_available2::<0x3FF>();
+        assert_eq!(pte.available2(), 0x3FF);
+        assert_eq!(u64::from(pte), 0x3FF0_0012_3456_0E00u64);
+
+        // Test TryFrom with ?=> for MemoryType
+        pte = pte.with_mem_type(MemoryType::Device);
+        assert_eq!(pte.mem_type(), Ok(MemoryType::Device));
+        assert_eq!(u64::from(pte), 0x3FF0_0012_3456_2E00u64);
+
+        pte = pte.with_mem_type(MemoryType::Normal);
+        assert_eq!(pte.mem_type(), Ok(MemoryType::Normal));
+        assert_eq!(u64::from(pte), 0x3FF0_0012_3456_1E00u64);
+
+        // Test all valid values for mem_type
+        pte = pte.with_mem_type(MemoryType::Reserved);
+        assert_eq!(pte.mem_type(), Ok(MemoryType::Reserved));
+        assert_eq!(u64::from(pte), 0x3FF0_0012_3456_3E00u64);
+
+        // Test failure case using mem_type field which has 4 bits (0-15)
+        // MemoryType only handles 0-3, so values 4-15 should return Err
+        let mut raw = pte.into_raw();
+        // Set bits 15:12 to 7 (invalid for MemoryType)
+        raw = (raw & !::kernel::bits::genmask_u64(12..=15)) | (0x7 << 12);
+        let invalid_pte = TestPageTableEntry::from_raw(raw);
+        // Should return Err with the invalid value
+        assert_eq!(invalid_pte.mem_type(), Err(0x7));
+
+        // Test a valid value after testing invalid to ensure both cases work
+        // Set bits 15:12 to 2 (valid: Device)
+        raw = (raw & !::kernel::bits::genmask_u64(12..=15)) | (0x2 << 12);
+        let valid_pte = TestPageTableEntry::from_raw(raw);
+        assert_eq!(valid_pte.mem_type(), Ok(MemoryType::Device));
+
+        const MAX_PFN: u64 = ::kernel::bits::genmask_u64(0..=35);
+        pte = pte.with_const_pfn::<{ MAX_PFN }>();
+        assert_eq!(pte.pfn(), MAX_PFN);
+    }
+
+    #[test]
+    fn test_builder_pattern() {
+        let pte = TestPageTableEntry::zeroed()
+            .with_present(true)
+            .with_writable(true)
+            .with_const_available::<0x7>()
+            .with_const_pfn::<0xABCDEF>()
+            .with_mem_type(MemoryType::Reserved)
+            .with_const_available2::<0x3FF>();
+
+        assert!(pte.present().into_bool());
+        assert!(pte.writable().into_bool());
+        assert_eq!(pte.available(), 0x7);
+        assert_eq!(pte.pfn(), 0xABCDEF);
+        assert_eq!(pte.mem_type(), Ok(MemoryType::Reserved));
+        assert_eq!(pte.available2(), 0x3FF);
+    }
+
+    #[test]
+    fn test_raw_operations() {
+        let raw_value = 0x3FF0000031233E03u64;
+
+        let pte = TestPageTableEntry::from_raw(raw_value);
+        assert_eq!(u64::from(pte), raw_value);
+
+        assert!(pte.present().into_bool());
+        assert!(pte.writable().into_bool());
+        assert_eq!(pte.available(), 0x7);
+        assert_eq!(pte.pfn(), 0x3123);
+        assert_eq!(pte.mem_type(), Ok(MemoryType::Reserved));
+        assert_eq!(pte.available2(), 0x3FF);
+
+        // Test using direct constructor syntax TestStruct(value)
+        let pte2 = TestPageTableEntry::from_raw(raw_value);
+        assert_eq!(u64::from(pte2), raw_value);
+    }
+
+    #[test]
+    fn test_u16_bitfield() {
+        let mut ctrl = TestControlRegister::zeroed();
+
+        assert!(!ctrl.enable().into_bool());
+        assert_eq!(ctrl.mode(), 0);
+        assert_eq!(ctrl.priority(), Priority::Low);
+        assert_eq!(ctrl.priority_nibble(), 0);
+        assert_eq!(ctrl.channel(), 0);
+
+        ctrl = ctrl.with_enable(true);
+        assert!(ctrl.enable().into_bool());
+
+        ctrl = ctrl.with_const_mode::<0x5>();
+        assert_eq!(ctrl.mode(), 0x5);
+
+        // Test From conversion with =>
+        ctrl = ctrl.with_priority(Priority::High);
+        assert_eq!(ctrl.priority(), Priority::High);
+        assert_eq!(ctrl.priority_nibble(), 0x2); // High = 2 in bits 5:4
+
+        ctrl = ctrl.with_channel(0xAB);
+        assert_eq!(ctrl.channel(), 0xAB);
+
+        // Test overlapping fields
+        ctrl = ctrl.with_const_priority_nibble::<0xF>();
+        assert_eq!(ctrl.priority_nibble(), 0xF);
+        assert_eq!(ctrl.priority(), Priority::Critical); // bits 5:4 = 0x3
+
+        let ctrl2 = TestControlRegister::zeroed()
+            .with_enable(true)
+            .with_const_mode::<0x3>()
+            .with_priority(Priority::Medium)
+            .with_channel(0x42);
+
+        assert!(ctrl2.enable().into_bool());
+        assert_eq!(ctrl2.mode(), 0x3);
+        assert_eq!(ctrl2.priority(), Priority::Medium);
+        assert_eq!(ctrl2.channel(), 0x42);
+
+        let raw_value: u16 = 0x4217;
+        let ctrl3 = TestControlRegister::from_raw(raw_value);
+        assert_eq!(u16::from(ctrl3), raw_value);
+        assert!(ctrl3.enable().into_bool());
+        assert_eq!(ctrl3.priority(), Priority::Medium);
+        assert_eq!(ctrl3.priority_nibble(), 0x1);
+        assert_eq!(ctrl3.channel(), 0x42);
+    }
+
+    #[test]
+    fn test_u8_bitfield() {
+        let mut status = TestStatusRegister::zeroed();
+
+        assert!(!status.ready().into_bool());
+        assert!(!status.error().into_bool());
+        assert_eq!(status.state(), 0);
+        assert_eq!(status.reserved(), 0);
+        assert_eq!(status.full_byte(), 0);
+
+        status = status.with_ready(true);
+        assert!(status.ready().into_bool());
+        assert_eq!(status.full_byte(), 0x01);
+
+        status = status.with_error(true);
+        assert!(status.error().into_bool());
+        assert_eq!(status.full_byte(), 0x03);
+
+        status = status.with_const_state::<0x3>();
+        assert_eq!(status.state(), 0x3);
+        assert_eq!(status.full_byte(), 0x0F);
+
+        status = status.with_const_reserved::<0xA>();
+        assert_eq!(status.reserved(), 0xA);
+        assert_eq!(status.full_byte(), 0xAF);
+
+        // Test overlapping field
+        status = status.with_full_byte(0x55);
+        assert_eq!(status.full_byte(), 0x55);
+        assert!(status.ready().into_bool());
+        assert!(!status.error().into_bool());
+        assert_eq!(status.state(), 0x1);
+        assert_eq!(status.reserved(), 0x5);
+
+        let status2 = TestStatusRegister::zeroed()
+            .with_ready(true)
+            .with_const_state::<0x2>()
+            .with_const_reserved::<0x5>();
+
+        assert!(status2.ready().into_bool());
+        assert!(!status2.error().into_bool());
+        assert_eq!(status2.state(), 0x2);
+        assert_eq!(status2.reserved(), 0x5);
+        assert_eq!(status2.full_byte(), 0x59);
+
+        let raw_value: u8 = 0x59;
+        let status3 = TestStatusRegister::from_raw(raw_value);
+        assert_eq!(u8::from(status3), raw_value);
+        assert!(status3.ready().into_bool());
+        assert!(!status3.error().into_bool());
+        assert_eq!(status3.state(), 0x2);
+        assert_eq!(status3.reserved(), 0x5);
+        assert_eq!(status3.full_byte(), 0x59);
+
+        let status4 = TestStatusRegister::from_raw(0xFF);
+        assert!(status4.ready().into_bool());
+        assert!(status4.error().into_bool());
+        assert_eq!(status4.state(), 0x3);
+        assert_eq!(status4.reserved(), 0xF);
+        assert_eq!(status4.full_byte(), 0xFF);
+    }
+}

-- 
2.53.0