[PATCH 3/4] rust: phy: add config_init, read_page, and write_page callbacks

[Artem Lytkin <iprintercanon@gmail.com>]

Add three new driver callbacks to the PHY abstraction:

  - config_init: Called to initialize the PHY after a reset. This is
    needed by nearly all real-world PHY drivers to configure
    vendor-specific registers (RGMII delays, LED settings, etc.).
    config_init was previously proposed in an RFC for the Rockchip PHY
    driver but not merged at that time. This re-introduces it in a
    form consistent with the existing vtable infrastructure.

  - read_page / write_page: Required by page-based PHY chips (Realtek,
    Marvell) for the kernel's paged register access infrastructure.
    When these callbacks are registered, phy_read_paged(),
    phy_write_paged(), and phy_modify_paged() use them to switch
    register pages. Both must be implemented together.

Each callback follows the established Adapter<T> pattern with
unsafe extern "C" fn bridging to the Rust Driver trait method, and
conditional registration in create_phy_driver() via HAS_* flags
generated by the #[vtable] macro.

Signed-off-by: Artem Lytkin <iprintercanon@gmail.com>
---
 rust/kernel/net/phy.rs | 83 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)

diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
index 43d1ee360268b..8fb34d34fe7de 100644
--- a/rust/kernel/net/phy.rs
+++ b/rust/kernel/net/phy.rs
@@ -390,6 +390,51 @@ struct Adapter<T: Driver> {
 }
 
 impl<T: Driver> Adapter<T> {
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn config_init_callback(phydev: *mut bindings::phy_device) -> c_int {
+        from_result(|| {
+            // SAFETY: The C core calls config_init with the PHY mutex held
+            // (from phy_init_hw), so the accessors on `Device` are okay to call.
+            let dev = unsafe { Device::from_raw(phydev) };
+            T::config_init(dev)?;
+            Ok(0)
+        })
+    }
+
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn read_page_callback(phydev: *mut bindings::phy_device) -> 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) };
+            let page = T::read_page(dev)?;
+            Ok(page.into())
+        })
+    }
+
+    /// # Safety
+    ///
+    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
+    unsafe extern "C" fn write_page_callback(
+        phydev: *mut bindings::phy_device,
+        page: c_int,
+    ) -> 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) };
+            let page = u16::try_from(page).map_err(|_| code::EINVAL)?;
+            T::write_page(dev, page)?;
+            Ok(0)
+        })
+    }
+
     /// # Safety
     ///
     /// `phydev` must be passed by the corresponding callback in `phy_driver`.
@@ -582,6 +627,11 @@ pub const fn create_phy_driver<T: Driver>() -> DriverVTable {
         flags: T::FLAGS,
         phy_id: T::PHY_DEVICE_ID.id(),
         phy_id_mask: T::PHY_DEVICE_ID.mask_as_int(),
+        config_init: if T::HAS_CONFIG_INIT {
+            Some(Adapter::<T>::config_init_callback)
+        } else {
+            None
+        },
         soft_reset: if T::HAS_SOFT_RESET {
             Some(Adapter::<T>::soft_reset_callback)
         } else {
@@ -632,6 +682,16 @@ pub const fn create_phy_driver<T: Driver>() -> DriverVTable {
         } else {
             None
         },
+        read_page: if T::HAS_READ_PAGE {
+            Some(Adapter::<T>::read_page_callback)
+        } else {
+            None
+        },
+        write_page: if T::HAS_WRITE_PAGE {
+            Some(Adapter::<T>::write_page_callback)
+        } else {
+            None
+        },
         link_change_notify: if T::HAS_LINK_CHANGE_NOTIFY {
             Some(Adapter::<T>::link_change_notify_callback)
         } else {
@@ -659,6 +719,11 @@ pub trait Driver {
     /// The default id and mask are zero.
     const PHY_DEVICE_ID: DeviceId = DeviceId::new_with_custom_mask(0, 0);
 
+    /// Called to initialize the PHY, including after a reset.
+    fn config_init(_dev: &mut Device) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
     /// Issues a PHY software reset.
     fn soft_reset(_dev: &mut Device) -> Result {
         build_error!(VTABLE_DEFAULT_ERROR)
@@ -711,6 +776,24 @@ fn write_mmd(_dev: &mut Device, _devnum: u8, _regnum: u16, _val: u16) -> Result
         build_error!(VTABLE_DEFAULT_ERROR)
     }
 
+    /// Returns the current PHY register page number.
+    ///
+    /// Must be implemented together with [`Driver::write_page`]. The kernel's
+    /// paged register access infrastructure requires both callbacks to be
+    /// present.
+    fn read_page(_dev: &mut Device) -> Result<u16> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
+    /// Sets the current PHY register page number.
+    ///
+    /// Must be implemented together with [`Driver::read_page`]. The kernel's
+    /// paged register access infrastructure requires both callbacks to be
+    /// present.
+    fn write_page(_dev: &mut Device, _page: u16) -> Result {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
     /// Callback for notification of link change.
     fn link_change_notify(_dev: &mut Device) {}
 }
-- 
2.43.0