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Date: Fri, 10 Jul 2026 01:00:09 +0200
Message-Id: <DJUEWLO5YJFE.3BKHFV0J9K3TA@kernel.org>
Subject: Re: [PATCH v4 2/6] rust: pci: add sriov_get_totalvfs() helper
Cc: <acourbot@nvidia.com>, <airlied@gmail.com>, <simona@ffwll.ch>,
 <ojeda@kernel.org>, <alex.gaynor@gmail.com>, <boqun.feng@gmail.com>,
 <gary@garyguo.net>, <bjorn3_gh@protonmail.com>, <lossin@kernel.org>,
 <a.hindborg@kernel.org>, <aliceryhl@google.com>, <tmgross@umich.edu>,
 <jhubbard@nvidia.com>, <ecourtney@nvidia.com>, <joelagnelf@nvidia.com>,
 <apopple@nvidia.com>, <cjia@nvidia.com>, <smitra@nvidia.com>,
 <kjaju@nvidia.com>, <alkumar@nvidia.com>, <ankita@nvidia.com>,
 <aniketa@nvidia.com>, <kwankhede@nvidia.com>, <targupta@nvidia.com>,
 <nova-gpu@lists.linux.dev>, <linux-kernel@vger.kernel.org>,
 <zhiwang@kernel.org>, "Bjorn Helgaas" <bhelgaas@google.com>, "David Laight"
 <david.laight.linux@gmail.com>, <linux-pci@vger.kernel.org>
To: "Zhi Wang" <zhiw@nvidia.com>
From: "Danilo Krummrich" <dakr@kernel.org>
References: <20260709150206.1046839-1-zhiw@nvidia.com>
 <20260709150206.1046839-3-zhiw@nvidia.com>
In-Reply-To: <20260709150206.1046839-3-zhiw@nvidia.com>

On Thu Jul 9, 2026 at 5:02 PM CEST, Zhi Wang wrote:
> +    /// Returns the total number of VFs, or [`None`] if SR-IOV is not av=
ailable.
> +    #[inline]
> +    pub fn sriov_get_totalvfs(&self) -> Option<NonZero<u16>> {
> +        // SAFETY: `self.as_raw()` is a valid pointer to a `struct pci_d=
ev`.
> +        let total_vfs =3D unsafe { bindings::pci_sriov_get_totalvfs(self=
.as_raw()) };
> +
> +        // CAST: The C function returns `unsigned int`, but the value or=
iginates
> +        // from TotalVFs/driver_max_VFs (which are defined as `u16`), so=
 this cast
> +        // cannot truncate.
> +        NonZero::new(total_vfs as u16)
> +    }
>  }
> =20
>  impl<'a> Device<device::Core<'a>> {

It is not a problem yet, but sriov_get_totalvfs() should go into the
Device<Core> impl above.

Once we also have sriov_set_totalvfs() this would otherwise be a potential =
data
race.