safe-mmio

The safe-mmio crate provides types to wrap registers that can be read or written safely.

# // Copyright 2025 Google LLC
# // SPDX-License-Identifier: Apache-2.0
#
{{#include ../examples/src/pl011.rs:Registers}}

• Reading dr has a side effect: it pops a byte from the receive FIFO.
• Reading rsr (and other registers) has no side-effects. It is a 'pure' read.

• There are a number of different crates providing safe abstractions around MMIO operations; we recommend the safe-mmio crate.
• The difference between ReadPure or ReadOnly (and likewise between ReadPureWrite and ReadWrite) is whether reading a register can have side-effects that change the state of the device, e.g., reading the data register pops a byte from the receive FIFO. ReadPure means that reads have no side-effects, they are purely reading data.