linux-kernel - Re: [RFC PATCH] pci: add pci_irq_get_affinity

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Date:   Tue, 8 Nov 2016 15:48:25 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Hannes Reinecke <hare@...e.de>
cc:     Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        linux-block@...r.kernel.org, linux-pci@...r.kernel.org,
        Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
        Hannes Reinecke <hare@...e.com>
Subject: Re: [RFC PATCH] pci: add pci_irq_get_affinity_vector()

On Tue, 8 Nov 2016, Hannes Reinecke wrote:

> Add a reverse-mapping function to return the interrupt vector for
> any CPU if interrupt affinity is enabled.
> 
> Signed-off-by: Hannes Reinecke <hare@...e.com>
> ---
>  drivers/pci/msi.c   | 36 ++++++++++++++++++++++++++++++++++++
>  include/linux/pci.h |  1 +
>  2 files changed, 37 insertions(+)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index bfdd074..de5ed32 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -1302,6 +1302,42 @@ const struct cpumask *pci_irq_get_affinity(struct pci_dev *dev, int nr)
>  }
>  EXPORT_SYMBOL(pci_irq_get_affinity);
>  
> +/**
> + * pci_irq_get_affinity_vector - return the vector number for a given CPU
> + * @dev:	PCI device to operate on
> + * @cpu:	cpu number
> + *
> + * Returns the vector number for CPU @cpu or a negative error number
> + * if interrupt affinity is not set.
> + */
> +int pci_irq_get_affinity_vector(struct pci_dev *dev, int cpu)
> +{
> +	if (dev->msix_enabled) {
> +		struct msi_desc *entry;
> +
> +		for_each_pci_msi_entry(entry, dev) {
> +			if (cpumask_test_cpu(cpu, entry->affinity))

entry->affinity can be NULL