Re: [RFC KERNEL PATCH v3 3/3] PCI/sysfs: Add gsi sysfs for pci_dev

["Roger Pau Monné" <roger.pau@citrix.com>]

On Mon, Dec 11, 2023 at 12:15:19AM +0800, Jiqian Chen wrote:
> There is a need for some scenarios to use gsi sysfs.
> For example, when xen passthrough a device to dumU, it will
> use gsi to map pirq, but currently userspace can't get gsi
> number.
> So, add gsi sysfs for that and for other potential scenarios.
> 
> Co-developed-by: Huang Rui <ray.huang@amd.com>
> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
> ---
>  drivers/acpi/pci_irq.c  |  1 +
>  drivers/pci/pci-sysfs.c | 11 +++++++++++
>  include/linux/pci.h     |  2 ++
>  3 files changed, 14 insertions(+)
> 
> diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c
> index 630fe0a34bc6..739a58755df2 100644
> --- a/drivers/acpi/pci_irq.c
> +++ b/drivers/acpi/pci_irq.c
> @@ -449,6 +449,7 @@ int acpi_pci_irq_enable(struct pci_dev *dev)
>  		kfree(entry);
>  		return 0;
>  	}
> +	dev->gsi = gsi;

It would be better if the gsi if fetched without requiring calling
acpi_pci_irq_enable(), as the gsi doesn't require the interrupt to be
enabled.  The gsi is known at boot time and won't change for the
lifetime of the device.

>  
>  	rc = acpi_register_gsi(&dev->dev, gsi, triggering, polarity);
>  	if (rc < 0) {
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 2321fdfefd7d..c51df88d079e 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -71,6 +71,16 @@ static ssize_t irq_show(struct device *dev,
>  }
>  static DEVICE_ATTR_RO(irq);
>  
> +static ssize_t gsi_show(struct device *dev,
> +			struct device_attribute *attr,
> +			char *buf)
> +{
> +	struct pci_dev *pdev = to_pci_dev(dev);

const

Thanks, Roger.