Add an optional bus callback sriov_configure() to pci::Driver trait,
using the vtable attribute to query if the driver implements the
callback. The callback is invoked when a user-space application
writes the number of VFs to the sysfs file `sriov_numvfs` to
enable SR-IOV, or zero to disable SR-IOV for a PCI device.

Suggested-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Peter Colberg <pcolberg@redhat.com>
---
 rust/kernel/pci.rs | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 24dda12f6402098a1a323f3b5aae884201b26d89..f9054c52a3bdff2c42273366a4058d943ee5fd76 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -66,6 +66,10 @@ unsafe fn register(
             (*pdrv.get()).probe = Some(Self::probe_callback);
             (*pdrv.get()).remove = Some(Self::remove_callback);
             (*pdrv.get()).id_table = T::ID_TABLE.as_ptr();
+            #[cfg(CONFIG_PCI_IOV)]
+            if T::HAS_SRIOV_CONFIGURE {
+                (*pdrv.get()).sriov_configure = Some(Self::sriov_configure_callback);
+            }
         }
 
         // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
@@ -118,6 +122,20 @@ extern "C" fn remove_callback(pdev: *mut bindings::pci_dev) {
 
         T::unbind(pdev, data.as_ref());
     }
+
+    #[cfg(CONFIG_PCI_IOV)]
+    extern "C" fn sriov_configure_callback(
+        pdev: *mut bindings::pci_dev,
+        nr_virtfn: c_int,
+    ) -> c_int {
+        // SAFETY: The PCI bus only ever calls the sriov_configure callback with a valid pointer to
+        // a `struct pci_dev`.
+        //
+        // INVARIANT: `pdev` is valid for the duration of `sriov_configure_callback()`.
+        let pdev = unsafe { &*pdev.cast::<Device<device::CoreInternal>>() };
+
+        from_result(|| T::sriov_configure(pdev, nr_virtfn))
+    }
 }
 
 /// Declares a kernel module that exposes a single PCI driver.
@@ -307,6 +325,39 @@ pub trait Driver: Send {
     fn unbind(dev: &Device<device::Core>, this: Pin<&Self>) {
         let _ = (dev, this);
     }
+
+    /// Single Root I/O Virtualization (SR-IOV) configure.
+    ///
+    /// Called when a user-space application enables or disables the SR-IOV capability for a
+    /// [`Device`] by writing the number of Virtual Functions (VF), `nr_virtfn` or zero to the
+    /// sysfs file `sriov_numvfs` for this device. Implementing this callback is optional.
+    ///
+    /// Upon success, this callback must return the number of VFs that were enabled, or zero if
+    /// SR-IOV was disabled.
+    ///
+    /// See [PCI Express I/O Virtualization].
+    ///
+    /// [PCI Express I/O Virtualization]: https://docs.kernel.org/PCI/pci-iov-howto.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use kernel::{device::Core, pci, prelude::*};
+    /// #[cfg(CONFIG_PCI_IOV)]
+    /// fn sriov_configure(dev: &pci::Device<Core>, nr_virtfn: i32) -> Result<i32> {
+    ///     if nr_virtfn == 0 {
+    ///         dev.disable_sriov();
+    ///     } else {
+    ///         dev.enable_sriov(nr_virtfn)?;
+    ///     }
+    ///     Ok(nr_virtfn)
+    /// }
+    /// ```
+    #[cfg(CONFIG_PCI_IOV)]
+    fn sriov_configure(dev: &Device<device::Core>, nr_virtfn: i32) -> Result<i32> {
+        let _ = (dev, nr_virtfn);
+        build_error!(crate::error::VTABLE_DEFAULT_ERROR)
+    }
 }
 
 /// The PCI device representation.

-- 
2.51.1

Hi Peter,

kernel test robot noticed the following build errors:

[auto build test ERROR on e4addc7cc2dfcc19f1c8c8e47f3834b22cb21559]

url:    https://github.com/intel-lab-lkp/linux/commits/Peter-Colberg/rust-pci-add-is_virtfn-to-check-for-VFs/20251120-062302
base:   e4addc7cc2dfcc19f1c8c8e47f3834b22cb21559
patch link:    https://lore.kernel.org/r/20251119-rust-pci-sriov-v1-6-883a94599a97%40redhat.com
patch subject: [PATCH 6/8] rust: pci: add bus callback sriov_configure(), to control SR-IOV from sysfs
config: um-randconfig-001-20251121 (https://download.01.org/0day-ci/archive/20251121/202511211317.FkJsCIc0-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 9e9fe08b16ea2c4d9867fb4974edf2a3776d6ece)
rustc: rustc 1.88.0 (6b00bc388 2025-06-23)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251121/202511211317.FkJsCIc0-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511211317.FkJsCIc0-lkp@intel.com/

All errors (new ones prefixed by >>):

>> error[E0609]: no field `sriov_configure` on type `pci_driver`
   --> rust/kernel/pci.rs:71:31
   |
   71 |                 (*pdrv.get()).sriov_configure = Some(Self::sriov_configure_callback);
   |                               ^^^^^^^^^^^^^^^ unknown field
   |
   = note: available field is: `_address`

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki