On 06.12.25 13:42, Zhi Wang wrote:
> Add a wrapper for the `pci_sriov_get_totalvfs()` helper, allowing drivers
> to query the number of total SR-IOV virtual functions a PCI device
> supports.
>
> This is useful for components that need to conditionally enable features
> based on SR-IOV capability.
>
> Signed-off-by: Zhi Wang <[email protected]>
> ---
> rust/kernel/pci.rs | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> index 7fcc5f6022c1..9a82e83dfd30 100644
> --- a/rust/kernel/pci.rs
> +++ b/rust/kernel/pci.rs
> @@ -514,6 +514,18 @@ 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 total number of VFs, or `Err(ENODEV)` if none available.
> + pub fn sriov_get_totalvfs(&self) -> Result<i32> {
> + // SAFETY: `self.as_raw()` is a valid pointer to a `struct pci_dev`.
> + let vfs = unsafe { bindings::pci_sriov_get_totalvfs(self.as_raw()) };
> +
> + if vfs != 0 {
> + Ok(vfs)
> + } else {
> + Err(ENODEV)
> + }
In the thread [1] there was some discussion about the `if {} else {}`
"style". From that discussion I "distilled" 6 options [2] which I
liked for having an overview :) Of course not all of these applied
there (const), neither will they here. And all have pros and cons. I
think in the end option #4 was selected.
What's about to do something similar here (and in the 2/7 patch as well)?
if vfs == 0 {
return Err(ENODEV);
}
Ok(vfs)
Dirk
[1]
https://lore.kernel.org/rust-for-linux/caniq72kisct5euaujcszvxmzm9hdj8aqgeun_pvf-vhf3dh...@mail.gmail.com/
[2] Options distilled from the thread [1]:
1.
if let Some(sum) = addr.checked_add(PAGE_SIZE - 1) {
return Some(sum & PAGE_MASK);
}
None
2.
addr.checked_add(PAGE_SIZE - 1).map(|sum| sum & PAGE_MASK)
3.
if let Some(sum) = addr.checked_add(PAGE_SIZE - 1) {
Some(sum & PAGE_MASK);
} else {
None
}
4.
let Some(sum) = addr.checked_add(PAGE_SIZE - 1) else {
return None;
};
Some(sum & PAGE_MASK)
5.
match addr.checked_add(PAGE_SIZE - 1) {
Some(v) => Some(v & PAGE_MASK),
None => None,
}
6.
Some(addr.checked_add(PAGE_SIZE - 1)? & PAGE_MASK)
