[PATCH v2 1/2] rust: pci: skip probing VFs if driver doesn't support VFs

[John Hubbard]

Add a "supports_vf" flag to struct pci_driver to let drivers declare
Virtual Function (VF) support. If a driver does not support VFs, then
the PCI driver core will not probe() any VFs for that driver's devices.

On the Rust side, add a const "SUPPORTS_VF" Driver trait, defaulting to
false: drivers must explicitly opt into VF support.

Cc: Alexandre Courbot <acourbot@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Joel Fernandes <joelagnelf@xxxxxxxxxx>
Cc: Zhi Wang <zhiw@xxxxxxxxxx>
Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Suggested-by: Danilo Krummrich <dakr@xxxxxxxxxx>
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---
 drivers/pci/pci-driver.c | 3 +++
 include/linux/pci.h      | 1 +
 rust/kernel/pci.rs       | 4 ++++
 3 files changed, 8 insertions(+)

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 63665240ae87..588666cc7254 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -412,6 +412,9 @@ static int __pci_device_probe(struct pci_driver *drv, struct pci_dev *pci_dev)
 	if (drv->probe) {
 		error = -ENODEV;
 
+		if (pci_dev->is_virtfn && !drv->supports_vf)
+			return error;
+
 		id = pci_match_device(drv, pci_dev);
 		if (id)
 			error = pci_call_probe(drv, pci_dev, id);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 59876de13860..92510886a086 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -983,6 +983,7 @@ struct pci_driver {
 	struct device_driver	driver;
 	struct pci_dynids	dynids;
 	bool driver_managed_dma;
+	bool supports_vf;	/* Will bind to Virtual Functions */
 };
 
 #define to_pci_driver(__drv)	\
diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 7fcc5f6022c1..c5d036770e65 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -47,6 +47,7 @@ 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();
+            (*pdrv.get()).supports_vf = T::SUPPORTS_VF;
         }
 
         // SAFETY: `pdrv` is guaranteed to be a valid `RegType`.
@@ -268,6 +269,9 @@ pub trait Driver: Send {
     /// The table of device ids supported by the driver.
     const ID_TABLE: IdTable<Self::IdInfo>;
 
+    /// Whether the driver supports Virtual Functions.
+    const SUPPORTS_VF: bool = false;
+
     /// PCI driver probe.
     ///
     /// Called when a new pci device is added or discovered. Implementers should
-- 
2.51.0