Re: [PATCH v7 07/16] rust: add `io::{Io, IoRaw}` base types

Danilo Krummrich
2025-01-20T12:54:45Z

On 1/16/25 11:31 AM, Fiona Behrens wrote:
> On 19 Dec 2024, at 18:04, Danilo Krummrich wrote:

>> +impl<const SIZE: usize> Io<SIZE> {
>> + /// Converts an `IoRaw` into an `Io` instance, providing the accessors to the MMIO mapping.
>> + ///
>> + /// # Safety
>> + ///
>> + /// Callers must ensure that `addr` is the start of a valid I/O mapped memory region of size
>> + /// `maxsize`.
>> + pub unsafe fn from_raw(raw: &IoRaw<SIZE>) -> &Self {
>> + // SAFETY: `Io` is a transparent wrapper around `IoRaw`.
>> + unsafe { &*core::ptr::from_ref(raw).cast() }
>> + }
>> +
>> + /// Returns the base address of this mapping.
>> + #[inline]
>> + pub fn addr(&self) -> usize {
>> + self.0.addr()
>> + }
>> +
>> + /// Returns the maximum size of this mapping.
>> + #[inline]
>> + pub fn maxsize(&self) -> usize {
>> + self.0.maxsize()
>> + }
>> +
>> + #[inline]
>> + const fn offset_valid(offset: usize, size: usize) -> bool {
>> + let type_size = core::mem::size_of::();
>> + if let Some(end) = offset.checked_add(type_size) {
>> + end <= size && offset % type_size == 0
>> + } else {
>> + false
>> + }
>> + }
>> +
>> + #[inline]
>> + fn io_addr(&self, offset: usize) -> Result<usize> {
>> + if !Self::offset_valid::(offset, self.maxsize()) {
>> + return Err(EINVAL);
>> + }
>> +
>> + // Probably no need to check, since the safety requirements of `Self::new` guarantee that
>> + // this can't overflow.
>> + self.addr().checked_add(offset).ok_or(EINVAL)
>> + }
>> +
>> + #[inline]
>> + fn io_addr_assert(&self, offset: usize) -> usize {
>> + build_assert!(Self::offset_valid::(offset, SIZE));
>> +
>> + self.addr() + offset
>> + }
>
> Currently reworking the portmem abstractions I wrote for the LED/SE10 driver.
> Right now I’m wondering if it would make sense to move the 3 functions above (`offset_valid`, `io_addr` and `io_addr_assert` into IoRaw),
> as I’m considering reusing the IoRaw in the portmem and then just offer the outb/outw/outl functions on a wraping type around IoRaw.
> For this I would also use the same functions to check bounds.

Sure, feel free to move them. I think I should have moved those functions to
IoRaw from the get-go.

- Danilo