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PeripheralRef docs improvements.

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Dario Nieuwenhuis 2023-02-03 06:36:10 +01:00 committed by GitHub
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embassy-hal-common/src/peripheral.rs
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@ -3,16 +3,17 @@ use core::ops::{Deref, DerefMut};
/// An exclusive reference to a peripheral. /// An exclusive reference to a peripheral.
/// ///
/// This is functionally the same as a `&'a mut T`. The reason for having a /// This is functionally the same as a `&'a mut T`. There's a few advantages in having
/// dedicated struct is memory efficiency: /// a dedicated struct instead:
/// ///
/// Peripheral singletons are typically either zero-sized (for concrete peripherals /// - Memory efficiency: Peripheral singletons are typically either zero-sized (for concrete
/// like `PA9` or `Spi4`) or very small (for example `AnyPin` which is 1 byte). /// peripherals like `PA9` or `SPI4`) or very small (for example `AnyPin`, which is 1 byte).
/// However `&mut T` is always 4 bytes for 32-bit targets, even if T is zero-sized. /// However `&mut T` is always 4 bytes for 32-bit targets, even if T is zero-sized.
/// PeripheralRef stores a copy of `T` instead, so it's the same size. /// PeripheralRef stores a copy of `T` instead, so it's the same size.
/// /// - Code size efficiency. If the user uses the same driver with both `SPI4` and `&mut SPI4`,
/// but it is the size of `T` not the size /// the driver code would be monomorphized two times. With PeripheralRef, the driver is generic
/// of a pointer. This is useful if T is a zero sized type. /// over a lifetime only. `SPI4` becomes `PeripheralRef<'static, SPI4>`, and `&mut SPI4` becomes
/// `PeripheralRef<'a, SPI4>`. Lifetimes don't cause monomorphization.
pub struct PeripheralRef<'a, T> { pub struct PeripheralRef<'a, T> {
inner: T, inner: T,
_lifetime: PhantomData<&'a mut T>, _lifetime: PhantomData<&'a mut T>,