netdev - Re: [PATCH] net-sysfs: expose IRQ number

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Date:   Mon, 29 Apr 2019 09:20:27 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Rafał Miłecki <zajec5@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Rafał Miłecki <rafal@...ecki.pl>
Subject: Re: [PATCH] net-sysfs: expose IRQ number

On Mon, 29 Apr 2019 08:01:07 +0200
Rafał Miłecki <zajec5@...il.com> wrote:

> From: Rafał Miłecki <rafal@...ecki.pl>
> 
> Knowing IRQ number makes e.g. reading /proc/interrupts much simpler.
> It's more reliable than guessing device name used by a driver when
> calling request_irq().
> 
> Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
> ---
> I found a script parsing /proc/interrupts for a given interface name. It wasn't
> working for me as it assumed request_irq() was called with a device name. It's
> not a case for all drivers.
> 
> I also found some other people looking for a proper solution for that:
> https://unix.stackexchange.com/questions/275075/programmatically-determine-the-irqs-associated-with-a-network-interface
> https://stackoverflow.com/questions/7516984/retrieving-irq-number-of-a-nic
> 
> Let me know if this solution makes sense. I can say it works for me ;)
> ---
>  Documentation/ABI/testing/sysfs-class-net |  7 +++++++
>  net/core/net-sysfs.c                      | 16 ++++++++++++++++
>  2 files changed, 23 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-net b/Documentation/ABI/testing/sysfs-class-net
> index 664a8f6a634f..33440fe77ca7 100644
> --- a/Documentation/ABI/testing/sysfs-class-net
> +++ b/Documentation/ABI/testing/sysfs-class-net
> @@ -301,3 +301,10 @@ Contact:	netdev@...r.kernel.org
>  Description:
>  		32-bit unsigned integer counting the number of times the link has
>  		been down
> +
> +What:		/sys/class/net/<iface>/irq
> +Date:		April 2019
> +KernelVersion:	5.2
> +Contact:	netdev@...r.kernel.org
> +Description:
> +		IRQ number used by device
> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> index e4fd68389d6f..a3eb7c3f1f37 100644
> --- a/net/core/net-sysfs.c
> +++ b/net/core/net-sysfs.c
> @@ -512,6 +512,21 @@ static ssize_t phys_switch_id_show(struct device *dev,
>  }
>  static DEVICE_ATTR_RO(phys_switch_id);
>  
> +static ssize_t irq_show(struct device *dev, struct device_attribute *attr,
> +			char *buf)
> +{
> +	const struct net_device *netdev = to_net_dev(dev);
> +	ssize_t ret;
> +
> +	if (!rtnl_trylock())
> +		return restart_syscall();
> +	ret = sprintf(buf, "%d\n", netdev->irq);
> +	rtnl_unlock();
> +
> +	return ret;
> +}
> +static DEVICE_ATTR_RO(irq);
> +
>  static struct attribute *net_class_attrs[] __ro_after_init = {
>  	&dev_attr_netdev_group.attr,
>  	&dev_attr_type.attr,
> @@ -542,6 +557,7 @@ static struct attribute *net_class_attrs[] __ro_after_init = {
>  	&dev_attr_proto_down.attr,
>  	&dev_attr_carrier_up_count.attr,
>  	&dev_attr_carrier_down_count.attr,
> +	&dev_attr_irq.attr,
>  	NULL,
>  };
>  ATTRIBUTE_GROUPS(net_class);

Can't you find this on the PCI side already?
$ ls /sys/class/net/eno1/device/msi_irqs/
37  38  39  40  41