Re: [PATCH 3/5] PCI: Set PCI_BUS_FLAGS_MSI_REMAP if MSI controller supports IRQ remapping

[Yongji Xie]

On 2016/5/25 5:04, Bjorn Helgaas wrote:

> On Wed, Apr 27, 2016 at 08:43:28PM +0800, Yongji Xie wrote:
> > On ARM HW the capability of IRQ remapping is abstracted on
> > MSI controller side. MSI_FLAG_IRQ_REMAPPING is used to advertise
> > this [1].
> >
> > To have a universal flag to test this capability for different
> > archs on PCI side, we set PCI_BUS_FLAGS_MSI_REMAP for PCI buses
> > when MSI_FLAG_IRQ_REMAPPING is set.
> >
> > [1] http://www.spinics.net/lists/kvm/msg130256.html
> >
> > Signed-off-by: Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
> > ---
> >   drivers/pci/msi.c   |   12 ++++++++++++
> >   drivers/pci/probe.c |    3 +++
> >   include/linux/msi.h |    6 +++++-
> >   3 files changed, 20 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> > index a080f44..1661cdf 100644
> > --- a/drivers/pci/msi.c
> > +++ b/drivers/pci/msi.c
> > @@ -1134,6 +1134,18 @@ void *msi_desc_to_pci_sysdata(struct msi_desc *desc)
> >   }
> >   EXPORT_SYMBOL_GPL(msi_desc_to_pci_sysdata);
> >   
> > +void pci_bus_check_msi_remapping(struct pci_bus *bus,
> > +				 struct irq_domain *domain)
> > +{
> > +#ifdef CONFIG_PCI_MSI_IRQ_DOMAIN
> > +	struct msi_domain_info *info;
> > +
> > +	info = msi_get_domain_info(domain);
> > +	if (info->flags & MSI_FLAG_IRQ_REMAPPING)
> > +		bus->bus_flags |= PCI_BUS_FLAGS_MSI_REMAP;
> > +#endif
> > +}
> Functions named "check_foo" are a pet peeve of mine because the name
> doesn't tell us anything about what the function *does*.  In this
> case, we know it checks something about MSI remapping, but we don't
> know whether we're checking whether it's enabled, disabled, or some
> other property.
>
> I'd prefer something like:
>
>    int pci_bus_msi_isolated(struct pci_bus *bus, struct irq_domain *domain)
>    {
>      struct msi_domain_info *info;
>
>      if (!domain)
>        return 0;
>
>      info = msi_get_domain_info(domain);
>      if (info->flags & MSI_FLAG_IRQ_REMAPPING)
>        return 1;
>
>      return 0;
>    }
>
>    void pci_set_bus_msi_domain(struct pci_bus *bus)
>    {
>      ...
>      if (b == bus && pci_bus_msi_isolated(bus, d))
>        bus->bus_flags |= PCI_BUS_FLAGS_MSI_REMAP;

Yes. This looks more reasonable. Thank you!

Regards,
Yongji