linux-kernel - Re: [Patch V2 13/13] genirq/msi: Provide helpers to return Linux IRQ/dev

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Date:   Thu, 25 Mar 2021 17:53:14 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Megha Dey <megha.dey@...el.com>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        dave.jiang@...el.com, ashok.raj@...el.com, kevin.tian@...el.com,
        dwmw@...zon.co.uk, x86@...nel.org, tony.luck@...el.com,
        dan.j.williams@...el.com, jgg@...lanox.com, kvm@...r.kernel.org,
        iommu@...ts.linux-foundation.org, alex.williamson@...hat.com,
        bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        baolu.lu@...ux.intel.com, ravi.v.shankar@...el.com
Subject: Re: [Patch V2 13/13] genirq/msi: Provide helpers to return Linux IRQ/dev_msi hw IRQ number

On Fri, 26 Feb 2021 20:11:17 +0000,
Megha Dey <megha.dey@...el.com> wrote:
> 
> From: Dave Jiang <dave.jiang@...el.com>
> 
> Add new helpers to get the Linux IRQ number and device specific index
> for given device-relative vector so that the drivers don't need to
> allocate their own arrays to keep track of the vectors and hwirq for
> the multi vector device MSI case.
> 
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> Signed-off-by: Dave Jiang <dave.jiang@...el.com>
> Signed-off-by: Megha Dey <megha.dey@...el.com>
> ---
>  include/linux/msi.h |  2 ++
>  kernel/irq/msi.c    | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 46 insertions(+)
> 
> diff --git a/include/linux/msi.h b/include/linux/msi.h
> index 24abec0..d60a6ba 100644
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -451,6 +451,8 @@ struct irq_domain *platform_msi_create_irq_domain(struct fwnode_handle *fwnode,
>  int platform_msi_domain_alloc_irqs(struct device *dev, unsigned int nvec,
>  				   irq_write_msi_msg_t write_msi_msg);
>  void platform_msi_domain_free_irqs(struct device *dev);
> +int msi_irq_vector(struct device *dev, unsigned int nr);
> +int dev_msi_hwirq(struct device *dev, unsigned int nr);
>  
>  /* When an MSI domain is used as an intermediate domain */
>  int msi_domain_prepare_irqs(struct irq_domain *domain, struct device *dev,
> diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
> index 047b59d..f2a8f55 100644
> --- a/kernel/irq/msi.c
> +++ b/kernel/irq/msi.c
> @@ -581,4 +581,48 @@ struct msi_domain_info *msi_get_domain_info(struct irq_domain *domain)
>  	return (struct msi_domain_info *)domain->host_data;
>  }
>  
> +/**
> + * msi_irq_vector - Get the Linux IRQ number of a device vector
> + * @dev: device to operate on
> + * @nr: device-relative interrupt vector index (0-based).
> + *
> + * Returns the Linux IRQ number of a device vector.
> + */
> +int msi_irq_vector(struct device *dev, unsigned int nr)
> +{
> +	struct msi_desc *entry;
> +	int i = 0;
> +
> +	for_each_msi_entry(entry, dev) {
> +		if (i == nr)
> +			return entry->irq;
> +		i++;

This obviously doesn't work with Multi-MSI, does it?

> +	}
> +	WARN_ON_ONCE(1);
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL_GPL(msi_irq_vector);
> +
> +/**
> + * dev_msi_hwirq - Get the device MSI hw IRQ number of a device vector
> + * @dev: device to operate on
> + * @nr: device-relative interrupt vector index (0-based).
> + *
> + * Return the dev_msi hw IRQ number of a device vector.
> + */
> +int dev_msi_hwirq(struct device *dev, unsigned int nr)
> +{
> +	struct msi_desc *entry;
> +	int i = 0;
> +
> +	for_each_msi_entry(entry, dev) {
> +		if (i == nr)
> +			return entry->device_msi.hwirq;
> +		i++;
> +	}
> +	WARN_ON_ONCE(1);
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL_GPL(dev_msi_hwirq);
> +
>  #endif /* CONFIG_GENERIC_MSI_IRQ_DOMAIN */

And what uses these helpers?

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.