Re: [PATCH v10 1/1] rust: pci: add extended capability and SR-IOV support

[Danilo Krummrich]

On Sun Sep 6, 2026 at 8:04 AM CEST, Zhi Wang wrote:
> +    pub fn vf_bars(&self) -> Result<impl Iterator<Item = ExtSriovVfBar>> {
> +        let slots: [u32; NUM_VF_BARS] =
> +            core::array::from_fn(|slot| crate::io_read!(*self, .vf_bar[panic: slot]));
> +        let mut slots = slots.into_iter();
> +        let mut bars = [None; NUM_VF_BARS];
> +        let mut count = 0;
> +
> +        let mut decode = || {
> +            while let Some(low) = slots.next().map(BarLow::from) {
> +                // SR-IOV VF BARs describe memory-space apertures; an I/O-space encoding is not
> +                // valid for these registers.
> +                if low.io_space() {
> +                    return Err(EINVAL);
> +                }
> +
> +                let low_address = u64::from(low.address()) << BarLow::ADDRESS_SHIFT;
> +                let bar = match low.memory_type()? {
> +                    BarMemoryType::Bits64 => ExtSriovVfBar {
> +                        address: (u64::from(slots.next().ok_or(EINVAL)?) << 32) | low_address,
> +                        is_64bit: true,
> +                    },
> +                    BarMemoryType::Bits32 => ExtSriovVfBar {
> +                        address: low_address,
> +                        is_64bit: false,
> +                    },
> +                };
> +
> +                bars[count] = Some(bar);
> +                count += 1;
> +            }
> +
> +            Ok(())
> +        };
> +
> +        decode().inspect_err(|_| {
> +            dev_err!(self.pdev, "invalid VF BAR encoding in SR-IOV capability\n");
> +        })?;
> +        Ok(bars.into_iter().flatten())
> +    }

I don't mind too much, but can you please remind me why we decode the VF BAR
registers and can't use the PCI core's VF resource information instead?

(I gave it a very quick try and using pci_bus_address() and pci_resource_flags()
actually turned out worse, but that could be me spending less than 5 minutes on
it. :)