On Thu, 23 Nov 2023 14:04:09 +0900
FUJITA Tomonori [off-list ref] wrote:

+    /// Reads a given C22 PHY register.
+    // This function reads a hardware register and updates the stats so takes `&mut self`.
+    pub fn read(&mut self, regnum: u16) -> Result<u16> {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        let ret = unsafe {
+            bindings::mdiobus_read((*phydev).mdio.bus, (*phydev).mdio.addr, regnum.into())
+        };
+        if ret < 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(ret as u16)
+        }
+    }
+
+    /// Writes a given C22 PHY register.
+    pub fn write(&mut self, regnum: u16, val: u16) -> Result {
+        let phydev = self.0.get();
+        // SAFETY: `phydev` is pointing to a valid object by the type invariant of `Self`.
+        // So an FFI call with a valid pointer.
+        to_result(unsafe {
+            bindings::mdiobus_write((*phydev).mdio.bus, (*phydev).mdio.addr, regnum.into(), val)
+        })
+    }

`read` and `write` are not very distinctive names, especially when
`read_paged` exists.

Maybe `mdio_{read,write}`?

+/// Defines certain other features this PHY supports (like interrupts).
+///
+/// These flag values are used in [`Driver::FLAGS`].
+pub mod flags {
+    /// PHY is internal.
+    pub const IS_INTERNAL: u32 = bindings::PHY_IS_INTERNAL;
+    /// PHY needs to be reset after the refclk is enabled.
+    pub const RST_AFTER_CLK_EN: u32 = bindings::PHY_RST_AFTER_CLK_EN;
+    /// Polling is used to detect PHY status changes.
+    pub const POLL_CABLE_TEST: u32 = bindings::PHY_POLL_CABLE_TEST;
+    /// Don't suspend.
+    pub const ALWAYS_CALL_SUSPEND: u32 = bindings::PHY_ALWAYS_CALL_SUSPEND;
+}
+
+/// An adapter for the registration of a PHY driver.
+struct Adapter<T: Driver> {
+    _p: PhantomData<T>,
+}
+
+impl<T: Driver> Adapter<T> {
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn soft_reset_callback(
+        phydev: *mut bindings::phy_device,
+    ) -> core::ffi::c_int {
+        from_result(|| {
+            // SAFETY: This callback is called only in contexts
+            // where we hold `phy_device->lock`, so the accessors on
+            // `Device` are okay to call.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::soft_reset(dev)?;

Usually we want type safety by to the callback typed access to the
device's driver-private data, rather than just give it an arbitrary
`Device`. Any reason not to similar things here?

+            Ok(0)
+        })
+    }
+}
+