I/O memory is typically either mapped through direct calls to ioremap() or subsystem / bus specific ones such as pci_iomap(). Even though subsystem / bus specific functions to map I/O memory are based on ioremap() / iounmap() it is not desirable to re-implement them in Rust. Instead, implement a base type for I/O mapped memory, which generically provides the corresponding accessors, such as `Io::readb` or `Io:try_readb`. `Io` supports an optional const generic, such that a driver can indicate the minimal expected and required size of the mapping at compile time. Correspondingly, calls to the 'non-try' accessors, support compile time checks of the I/O memory offset to read / write, while the 'try' accessors, provide boundary checks on runtime. `IoRaw` is meant to be embedded into a structure (e.g. pci::Bar or io::IoMem) which creates the actual I/O memory mapping and initializes `IoRaw` accordingly. To ensure that I/O mapped memory can't out-live the device it may be bound to, subsystems must embed the corresponding I/O memory type (e.g. pci::Bar) into a `Devres` container, such that it gets revoked once the device is unbound. Reviewed-by: Alice Ryhl <aliceryhl@google.com> Tested-by: Daniel Almeida <daniel.almeida@collabora.com> Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com> Signed-off-by: Danilo Krummrich <dakr@kernel.org> Tested-by: Dirk Behme <dirk.behme@de.bosch.com> Link: https://lore.kernel.org/r/20241219170425.12036-8-dakr@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>