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 <zhiw at nvidia.com>
---
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)
+ }
+ }
}
impl Device<device::Bound> {
--
2.51.0
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 <zhiw at nvidia.com> > --- > 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-vHf3DhBuQ at 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)
Alexandre Courbot
2025-Dec-09 03:42 UTC
[RFC 1/7] rust: pci: expose sriov_get_totalvfs() helper
On Sat Dec 6, 2025 at 9:42 PM JST, 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 <zhiw at nvidia.com> > --- > 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> {The return type if `pci_sriov_get_totalvfs` is a bit unfortunate. It returns `driver_max_VFs`, which is a `u16` [1], but not before implicitly converting it to an `int` - even though it doesn't make use of negative values to indicate errors! Even its C callers eventually compare its returned value to a `u16` [2]. How about a cleanup patch to fix it to return `u16`, so we can make the Rust wrapper return a `Result<NonZero<u16>>`? [1] https://elixir.bootlin.com/linux/v6.18/source/drivers/pci/iov.c#L1281 [2] https://elixir.bootlin.com/linux/v6.18/source/drivers/pci/iov.c#L474
On Sun, 7 Dec 2025 08:12:10 +0100 Dirk Behme <dirk.behme at gmail.com> wrote:> On 06.12.25 13:42, Zhi Wang wrote:snip> 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 >Hey Dirk: Thanks for the detailed summary! As a C programmer before, I tend to do as above, because it improves a lot of readability on success path. While playing with rust, I tend to use 5). Personally, I try to stay away from if let chains, as some lifecycle changes happen in rust 2024 [1]. It wouldn't bite right now, but stay away from the bumps. :) As Miguel's comment in another thread, I would improve this as discussed. [1] https://doc.rust-lang.org/edition-guide/rust-2024/temporary-if-let-scope.html> [1] > https://lore.kernel.org/rust-for-linux/CANiq72kiscT5euAUjcSzvxMzM9Hdj8aQGeUN_pVF-vHf3DhBuQ at 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) >
Alexandre Courbot
2025-Dec-10 11:31 UTC
[RFC 1/7] rust: pci: expose sriov_get_totalvfs() helper
On Sat Dec 6, 2025 at 9:42 PM JST, 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 <zhiw at nvidia.com> > --- > 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()) };This results in a build error if CONFIG_PCI_IOV is not set: error[E0425]: cannot find function `pci_sriov_get_totalvfs` in crate `bindings` --> ../rust/kernel/pci.rs:521:38 | 521 | let vfs = unsafe { bindings::pci_sriov_get_totalvfs(self.as_raw()) }; | ^^^^^^^^^^^^^^^^^^^^^^ not found in `bindings` error: aborting due to 1 previous error