[PATCH v2 3/6] rust: io: add new Io type

[Andrew Ballance <andrewjballance@gmail.com>]

adds a new Io type that uses the C ioread/iowrite family of functions
and implements the IoAccess trait for it and renames the old `Io`
to `MMIo`.

Signed-off-by: Andrew Ballance <andrewjballance@gmail.com>
---
 rust/helpers/io.c |  7 ++++
 rust/kernel/io.rs | 97 ++++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 98 insertions(+), 6 deletions(-)

diff --git a/rust/helpers/io.c b/rust/helpers/io.c
index d419b5b3b7c7..a138914523c8 100644
--- a/rust/helpers/io.c
+++ b/rust/helpers/io.c
@@ -52,3 +52,10 @@ define_rust_io_write_helper(rust_helper_writel_relaxed, writel_relaxed, u32);
 define_rust_io_write_helper(rust_helper_writeq_relaxed, writeq_relaxed, u64);
 #endif
 
+define_rust_io_read_helper(rust_helper_ioread8, ioread8, u8);
+define_rust_io_read_helper(rust_helper_ioread16, ioread16, u16);
+define_rust_io_read_helper(rust_helper_ioread32, ioread32, u32);
+
+define_rust_io_write_helper(rust_helper_iowrite8, iowrite8, u8);
+define_rust_io_write_helper(rust_helper_iowrite16, iowrite16, u16);
+define_rust_io_write_helper(rust_helper_iowrite32, iowrite32, u32);
diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index 368167d57863..ce044c155b16 100644
--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -264,9 +264,9 @@ pub fn maxsize(&self) -> usize {
 /// [`read`]: https://docs.kernel.org/driver-api/device-io.html#differences-between-i-o-access-functions
 /// [`write`]: https://docs.kernel.org/driver-api/device-io.html#differences-between-i-o-access-functions
 #[repr(transparent)]
-pub struct Io<const SIZE: usize = 0>(IoRaw<SIZE>);
+pub struct MMIo<const SIZE: usize = 0>(IoRaw<SIZE>);
 
-impl<const SIZE: usize> Io<SIZE> {
+impl<const SIZE: usize> MMIo<SIZE> {
     /// Convert a [`IoRaw`] into an [`MMIo`] instance, providing the accessors to the MMIO mapping.
     ///
     /// # Safety
@@ -293,7 +293,7 @@ pub unsafe fn from_raw_ref(raw: &IoRaw<SIZE>) -> &Self {
 }
 
 // SAFETY: as per invariant `raw` is valid
-unsafe impl<const SIZE: usize> IoAccess<SIZE> for Io<SIZE> {
+unsafe impl<const SIZE: usize> IoAccess<SIZE> for MMIo<SIZE> {
     #[inline]
     fn maxsize(&self) -> usize {
         self.0.maxsize()
@@ -312,13 +312,13 @@ fn addr(&self) -> usize {
 }
 
 #[cfg(CONFIG_64BIT)]
-impl<const SIZE: usize> IoAccess64<SIZE> for Io<SIZE> {
+impl<const SIZE: usize> IoAccess64<SIZE> for MMIo<SIZE> {
     impl_accessor_fn!(
         read64_unchecked, readq, write64_unchecked, writeq, u64;
     );
 }
 
-impl<const SIZE: usize> IoAccessRelaxed<SIZE> for Io<SIZE> {
+impl<const SIZE: usize> IoAccessRelaxed<SIZE> for MMIo<SIZE> {
     impl_accessor_fn!(
         read8_relaxed_unchecked, readb_relaxed, write8_relaxed_unchecked, writeb_relaxed, u8;
         read16_relaxed_unchecked, readw_relaxed, write16_relaxed_unchecked, writew_relaxed, u16;
@@ -327,8 +327,93 @@ impl<const SIZE: usize> IoAccessRelaxed<SIZE> for Io<SIZE> {
 }
 
 #[cfg(CONFIG_64BIT)]
-impl<const SIZE: usize> IoAccess64Relaxed<SIZE> for Io<SIZE> {
+impl<const SIZE: usize> IoAccess64Relaxed<SIZE> for MMIo<SIZE> {
     impl_accessor_fn!(
         read64_relaxed_unchecked, readq_relaxed, write64_relaxed_unchecked, writeq_relaxed, u64;
     );
 }
+
+/// Io that can be either PortIo or MMIo,
+/// starting at the base address [`addr`] and spanning [`maxsize`] bytes.
+///
+/// The creator (usually a subsystem / bus such as PCI) is responsible for creating the
+/// mapping, performing an additional region request, etc.
+///
+/// # Invariants
+///
+/// [`addr`] is the start and [`maxsize`] the length of a valid io region of size [`maxsize`].
+///
+/// [`addr`] is valid to access with the C [`ioread`]/[`iowrite`] family of functions.
+///
+/// [`addr`]: IoAccess::addr
+/// [`maxsize`]: IoAccess::maxsize
+/// [`ioread`]: https://docs.kernel.org/driver-api/device-io.html#differences-between-i-o-access-functions
+/// [`iowrite`]: https://docs.kernel.org/driver-api/device-io.html#differences-between-i-o-access-functions
+#[repr(transparent)]
+pub struct Io<const SIZE: usize = 0>(IoRaw<SIZE>);
+
+impl<const SIZE: usize> Io<SIZE> {
+    /// Convert a [`IoRaw`] into an [`Io`] instance, providing the accessors to the
+    /// Io mapping.
+    ///
+    /// # Safety
+    ///
+    /// Callers must ensure that `addr` is the start of a valid I/O region of size `maxsize`.
+    ///
+    /// ```
+    /// use kernel::io::{IoRaw, Io, IoAccess};
+    ///
+    /// let raw = IoRaw::<2>::new(0xDEADBEEFC0DE, 2).unwrap();
+    /// // SAFETY: test, value is not actually written to.
+    /// let io: Io<2> = unsafe { Io::from_raw(raw) };
+    /// # assert_eq!(0xDEADBEEFC0DE, io.addr());
+    /// # assert_eq!(2, io.maxsize());
+    /// ```
+    pub unsafe fn from_raw(raw: IoRaw<SIZE>) -> Self {
+        Self(raw)
+    }
+
+    /// Convert a ref to [`IoRaw`] into an [`Io`] instance, providing the accessors to
+    /// the Io mapping.
+    ///
+    /// # Safety
+    ///
+    /// Callers must ensure that `addr` is the start of a valid I/O mapped memory region of
+    /// size `maxsize`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use kernel::io::{IoRaw, Io, IoAccess};
+    ///
+    /// let raw = IoRaw::<2>::new(0xDEADBEEFC0DE, 2).unwrap();
+    /// // SAFETY: test, value is not actually written to.
+    /// let io: &Io<2> = unsafe { Io::from_raw_ref(&raw) };
+    /// # assert_eq!(raw.addr(), io.addr());
+    /// # assert_eq!(raw.maxsize(), io.maxsize());
+    /// ```
+    #[inline]
+    pub unsafe fn from_raw_ref(raw: &IoRaw<SIZE>) -> &Self {
+        // SAFETY: `Io` is a transparent wrapper around `IoRaw`.
+        unsafe { &*core::ptr::from_ref(raw).cast() }
+    }
+}
+
+// SAFETY: as per invariant `raw` is valid
+unsafe impl<const SIZE: usize> IoAccess<SIZE> for Io<SIZE> {
+    #[inline]
+    fn addr(&self) -> usize {
+        self.0.addr()
+    }
+
+    #[inline]
+    fn maxsize(&self) -> usize {
+        self.0.maxsize()
+    }
+
+    impl_accessor_fn!(
+        read8_unchecked, ioread8, write8_unchecked, iowrite8, u8;
+        read16_unchecked, ioread16, write16_unchecked, iowrite16, u16;
+        read32_unchecked, ioread32, write32_unchecked, iowrite32, u32;
+    );
+}
-- 
2.49.0