Re: [dpdk-dev] [PATCH v2 09/10] igbuio: show irq mode in sysfs

[Neil Horman <nhorman@tuxdriver.com>]

On Wed, Jun 11, 2014 at 06:27:35PM +0000, Carew, Alan wrote:
> > -----Original Message-----
> > From: Neil Horman [mailto:nhorman@tuxdriver.com]
> > Sent: Sunday, June 08, 2014 4:37 PM
> > To: Stephen Hemminger
> > Cc: Carew, Alan; dev@dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH v2 09/10] igbuio: show irq mode in sysfs
> > 
> > On Fri, Jun 06, 2014 at 04:50:37PM -0700, Stephen Hemminger wrote:
> > > Since irq mode is determined dynamically on a per-device
> > > basis, and virtio needs to know if using intx or msi-x,
> > > make it a sysfs attribute.
> > >
> > > --- a/lib/librte_eal/linuxapp/igb_uio/igb_uio.c
> > > +++ b/lib/librte_eal/linuxapp/igb_uio/igb_uio.c
> > > @@ -43,6 +43,10 @@
> > >  	IGBUIO_MSIX_INTR_MODE
> > >  };
> > >
> > > +static const char *igbuio_intr_modes[] = {
> > > +	"legacy", "msi", "msix"
> > > +};
> > > +
> > >  /**
> > >   * A structure describing the private information for a uio device.
> > >   */
> > > @@ -128,8 +132,20 @@
> > >  }
> > >
> > >  static DEVICE_ATTR(max_vfs, S_IRUGO | S_IWUSR, show_max_vfs,
> > store_max_vfs);
> > > +
> > > +static ssize_t irq_mode_show(struct device *dev,
> > > +			     struct device_attribute *attr, char *buf)
> > > +{
> > > +	struct uio_info *info = pci_get_drvdata(to_pci_dev(dev));
> > > +	struct rte_uio_pci_dev *udev = igbuio_get_uio_pci_dev(info);
> > > +
> > > +	return sprintf(buf, "%s\n", igbuio_intr_modes[udev->mode]);
> > > +}
> > > +static DEVICE_ATTR(irq_mode, S_IRUGO, irq_mode_show, NULL);
> > > +
> > >  static struct attribute *dev_attrs[] = {
> > >  	&dev_attr_max_vfs.attr,
> > > +	&dev_attr_irq_mode.attr,
> > >  	NULL,
> > >  };
> > >
> > >
> > >
> > Do you really need this attribute?  The pci bus sysfs tree already exports irq
> > mode information for each device allocated already in
> > /sys/bus/pci/device/msi_irqs<irq_number>
> > 
> > Neil
> 
> Hi Neil,
> 
> After some digging around, I now realise what you mean, it is a good suggestion.
thanks.

> /sys/bus/pci/devices/<D:B:D.F>/msi_irqs/<IRQ>/mode, where "msi_irqs" directory only exists for msi/msix and not for int-x. Also the "mode" file contains string of configured interrupt mode.
Yes, thats correct (although the file layout is slightly different in later
kernels, as the mode is contained in a file that is named after the irq vector).
For int-x interrupts you can query the /sys/bus/pci/devices/<D:B:D.F/irq file.

Best
Neil

> 
> Thanks,
> Alan
>