It looks like:

```rust
/// Shareability for an MPU Region
#[derive(Debug, PartialEq, Eq)]
#[bitbybit::bitenum(u2, exhaustive = true)]
pub enum Shareability {
    /// Non-shareable
    NonShareable = 0b00,
    /// Reserved
    Reserved = 0b01,
    /// Outer-Shareable
    OuterShareable = 0b10,
    /// Inner-Shareable
    InnerShareable = 0b11,
}
```