Re: [PATCH v2 02/13] PCI/IOV: Introduce VF iterators

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Oct 27, 2026 at 05:04:35PM +0100, Lukasz Laguna wrote:
> Introduce helpers to iterate over the enabled VFs of a PF. Add
> pci_get_vf() and pci_get_vf_reverse() to retrieve the next enabled VF
> of a PF in ascending or descending VF ID order, along with
> for_each_pci_vf(), for_each_pci_vf_reverse(), and
> for_each_pci_vf_continue_reverse() built on top of them. The helpers
> return each VF with a reference held, matching existing PCI device
> lookup APIs.
> 
> This provides a common and convenient way to iterate over a PF's enabled
> VFs and avoids duplicating the iteration logic in drivers.
> 
> Assisted-by: LLM
> Signed-off-by: Lukasz Laguna <lukasz.laguna@intel.com>
> ---
>  drivers/pci/iov.c   | 63 +++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pci.h | 57 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 120 insertions(+)
> 
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index eb019201faed..a437370c4e36 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -70,6 +70,69 @@ struct pci_dev *pci_iov_get_virtfn(struct pci_dev *dev, int id)
>  }
>  EXPORT_SYMBOL_GPL(pci_iov_get_virtfn);
>  
> +/**
> + * pci_get_vf() - Return the first or next existing VF of a PF
> + * @dev: PCI PF whose VFs are being iterated
> + * @from: Previous VF returned by this function, or %NULL to return the first VF
> + *
> + * Iterate over existing VFs of @dev in ascending VF ID order, skipping VF IDs
> + * with no device present. If a VF is found, its reference count is incremented.
> + * A new iteration is started by passing %NULL as the @from argument. Otherwise,
> + * iteration continues after @from, and the reference count on @from is
> + * decremented.
> + *
> + * Return: a pointer to the first or next VF, or %NULL if no further VF is found.
> + */
> +struct pci_dev *pci_get_vf(struct pci_dev *dev, struct pci_dev *from)
> +{
> +	int id = 0;
> +
> +	if (from) {
> +		id = pci_iov_vf_id(from) + 1;
> +		pci_dev_put(from);
> +	}
> +
> +	for (; id < pci_num_vf(dev); id++) {
> +		from = pci_iov_get_virtfn(dev, id);
> +		if (from)
> +			return from;
> +	}
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL_GPL(pci_get_vf);
> +
> +/**
> + * pci_get_vf_reverse() - Return the last or previous existing VF of a PF
> + * @dev: PCI PF whose VFs are being iterated
> + * @from: Previous VF returned by this function, or %NULL to return the last VF
> + *
> + * Same semantics as pci_get_vf(), except iteration proceeds in descending VF
> + * ID order.
> + *
> + * Return: a pointer to the last or previous VF, or %NULL if no further VF is
> + * found.
> + */
> +struct pci_dev *pci_get_vf_reverse(struct pci_dev *dev, struct pci_dev *from)
> +{
> +	int id = pci_num_vf(dev);
> +
> +	if (from) {
> +		id = pci_iov_vf_id(from);
> +		pci_dev_put(from);
> +	}
> +
> +	while (id > 0) {
> +		id--;
> +		from = pci_iov_get_virtfn(dev, id);
> +		if (from)
> +			return from;
> +	}

Seems slightly odd to use different loop control in pci_get_vf() and
pci_get_vf_reverse().  I think I would use "while" in pci_get_vf() to
match, obviously with id++ at the tail.

> +	return NULL;
> +}
> +EXPORT_SYMBOL_GPL(pci_get_vf_reverse);