Expose a safe Rust wrapper for the `cfg_size` field of `struct pci_dev`,
allowing drivers to query the size of a device's configuration space.

This is useful for code that needs to know whether the device supports
extended configuration space (e.g. 256 vs 4096 bytes) when accessing PCI
configuration registers and apply runtime checks.

Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
 rust/kernel/pci.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 77a8eb39ad32..34729c6f5665 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -514,6 +514,12 @@ pub fn pci_class(&self) -> Class {
         // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
         Class::from_raw(unsafe { (*self.as_raw()).class })
     }
+
+    /// Returns the size of configuration space.
+    pub fn cfg_size(&self) -> i32 {
+        // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
+        unsafe { (*self.as_raw()).cfg_size }
+    }
 }
 
 impl Device<device::Bound> {
-- 
2.47.3

On Thu Oct 16, 2025 at 11:02 PM CEST, Zhi Wang wrote:
> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> index 77a8eb39ad32..34729c6f5665 100644
> --- a/rust/kernel/pci.rs
> +++ b/rust/kernel/pci.rs
> @@ -514,6 +514,12 @@ pub fn pci_class(&self) -> Class {
>          // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
>          Class::from_raw(unsafe { (*self.as_raw()).class })
>      }
> +
> +    /// Returns the size of configuration space.
> +    pub fn cfg_size(&self) -> i32 {
> +        // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
> +        unsafe { (*self.as_raw()).cfg_size }
> +    }
>  }

This should probably return an enum type:

	enum ConfigSize {
		Normal = 256,
		Extended = 4096,
	}