Re: [PATCH] genirq/msi: Add the address and data that show MSI/MSIX

[Hans Zhang]

On 2025/2/28 00:39, Manivannan Sadhasivam wrote:
> On Fri, Feb 28, 2025 at 12:28:21AM +0800, Hans Zhang wrote:
> > Add to view the addresses and data stored in the MSI capability or the
> > addresses and data stored in the MSIX vector table.
> >
> > e.g.
> > root@root:/sys/bus/pci/devices/<dev>/msi_irqs# ls
> > 86  87  88  89
> > root@root:/sys/bus/pci/devices/<dev>/msi_irqs# cat *
> > msix
> >   address_hi: 0x00000000
> >   address_lo: 0x0e060040
> >   msg_data: 0x00000000
> > msix
> >   address_hi: 0x00000000
> >   address_lo: 0x0e060040
> >   msg_data: 0x00000001
> > msix
> >   address_hi: 0x00000000
> >   address_lo: 0x0e060040
> >   msg_data: 0x00000002
> > msix
> >   address_hi: 0x00000000
> >   address_lo: 0x0e060040
> >   msg_data: 0x00000003
> >
> > Signed-off-by: Hans Zhang <18255117159@xxxxxxx>
> > ---
> >   kernel/irq/msi.c | 12 +++++++++++-
> >   1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
> > index 396a067a8a56..a37a3e535fb8 100644
> > --- a/kernel/irq/msi.c
> > +++ b/kernel/irq/msi.c
> > @@ -503,8 +503,18 @@ static ssize_t msi_mode_show(struct device *dev, struct device_attribute *attr,
> >   {
> >   	/* MSI vs. MSIX is per device not per interrupt */
> >   	bool is_msix = dev_is_pci(dev) ? to_pci_dev(dev)->msix_enabled : false;
> > +	struct msi_desc *desc;
> > +	u32 irq;
> > +
> > +	if (kstrtoint(attr->attr.name, 10, &irq) < 0)
> > +		return 0;
> >   
> > -	return sysfs_emit(buf, "%s\n", is_msix ? "msix" : "msi");
> > +	desc = irq_get_msi_desc(irq);
> > +	return sysfs_emit(
> > +		buf,
> > +		"%s\n address_hi: 0x%08x\n address_lo: 0x%08x\n msg_data: 0x%08x\n",
> > +		is_msix ? "msix" : "msi", desc->msg.address_hi,
> > +		desc->msg.address_lo, desc->msg.data);
>
> Sysfs is an ABI. You cannot change the semantics of an attribute.

Thanks Mani for the tip.

If I want to implement similar functionality, where should I add it? 
Since this sysfs node is the only one that displays the MSI/MSIX 
interrupt number, I don't know where to implement similar debug 
functionality at this time. Do you have any suggestions? Or it shouldn't 
have a similar function.

Best regards
Hans