Subject: Re: [PATCH] skge: use unique IRQ name

From: Stephen Hemminger <[email-masked]>
Date: Thu, 1 Oct 2009 09:06:13 -0700

On Thu, 1 Oct 2009 12:27:20 +0200
Michal Schmidt <[email-masked]> wrote:

> Most network drivers request their IRQ when the interface is activated.
> skge does it in ->probe() instead, because it can work with two-port
> cards where the two net_devices use the same IRQ. This works fine most
> of the time, except in some situations when the interface gets renamed.
> Consider this example:
> 
> 1. modprobe skge
>    The card is detected as eth0 and requests IRQ 17. Directory
>    /proc/irq/17/eth0 is created.
> 2. There is an udev rule which says this interface should be called
>    eth1, so udev renames eth0 -> eth1.
> 3. modprobe 8139too
>    The Realtek card is detected as eth0. It will be using IRQ 17 too.
> 4. ip link set eth0 up
>    Now 8139too requests IRQ 17.
> 
> The result is:
> WARNING: at fs/proc/generic.c:590 proc_register ...
> proc_dir_entry '17/eth0' already registered
> ...
> And "ls /proc/irq/17" shows two subdirectories, both called eth0.
> 
> Fix it by using a unique name for skge's IRQ, based on the PCI address.
> The naming from the example then looks like this:
> $ grep skge /proc/interrupts
>  17:        169   IO-APIC-fasteoi   skge@0000:00:0a.0, eth0
> 
> irqbalance daemon will have to be taught to recognize "skge@" as an
> Ethernet interrupt. This will be a one-liner addition in classify.c. I
> will send a patch to irqbalance if this change is accepted.
> 
> Signed-off-by: Michal Schmidt <[email-masked]>
> 
> Index: kernel/drivers/net/skge.c
> ===================================================================
> --- kernel.orig/drivers/net/skge.c
> +++ kernel/drivers/net/skge.c
> @@ -3895,6 +3895,7 @@ static int __devinit skge_probe(struct p
>  	struct net_device *dev, *dev1;
>  	struct skge_hw *hw;
>  	int err, using_dac = 0;
> +	size_t irq_name_len;
>  
>  	err = pci_enable_device(pdev);
>  	if (err) {
> @@ -3935,11 +3936,13 @@ static int __devinit skge_probe(struct p
>  #endif
>  
>  	err = -ENOMEM;
> -	hw = kzalloc(sizeof(*hw), GFP_KERNEL);
> +	irq_name_len = strlen(DRV_NAME) + strlen(dev_name(&pdev->dev)) + 2;
> +	hw = kzalloc(sizeof(*hw) + irq_name_len, GFP_KERNEL);
>  	if (!hw) {
>  		dev_err(&pdev->dev, "cannot allocate hardware struct\n");
>  		goto err_out_free_regions;
>  	}
> +	sprintf(hw->irq_name, DRV_NAME "@%s", dev_name(&pdev->dev));

I like this with one small change. Please use:
         skge@pci:0000:00:02.0
This makes the driver follow same format as existing DRM graphics drivers.
Michal could you follow up with additional patches for:
   1. sky2 driver has same issue
   2. irqbalance has a list of special drivers that needs to be updated