[RFC,1/2] Implementation of pci_fixup_irqs for descendants of a specified bus

Continuing from discussion with Thierry (lkml.org/lkml/2013/1/18/107) perhaps
this will be useful to fold into your patchset. 
---
This patch provides pci_bus_fixup_irqs which performs the same
function as pci_fixup_irqs but only to descendants of the specified
bus.

This can reduce unnecessary fixing up of device irqs when new buses
are added.

Signed-off-by: Andrew Murray <Andrew.Murray@arm.com>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
---
 drivers/pci/setup-irq.c |   15 +++++++++++++++
 include/linux/pci.h     |    3 +++
 2 files changed, 18 insertions(+), 0 deletions(-)

On Fri, Jan 18, 2013 at 4:37 AM, Andrew Murray <Andrew.Murray@arm.com> wrote:
> Continuing from discussion with Thierry (lkml.org/lkml/2013/1/18/107) perhaps
> this will be useful to fold into your patchset.
> ---
> This patch provides pci_bus_fixup_irqs which performs the same
> function as pci_fixup_irqs but only to descendants of the specified
> bus.

I think pci_fixup_irqs() is a broken design to begin with because it
is only called once at boot-time and it iterates over all the devices
we've found so far.  Any hot-added devices never get the fixups.

Adding pci_bus_fixup_irqs() addresses part of that, by adding a way to
fixup a subset of devices, e.g., maybe it could be done for hot-added
things.

But I think it would be better to do a more extensive refactoring and
do the IRQ fixups directly somewhere in the pci_device_add() path.
That way we can do it a device at a time, for every device (present at
boot and hot-added later), and before any drivers claim the device.

> This can reduce unnecessary fixing up of device irqs when new buses
> are added.
>
> Signed-off-by: Andrew Murray <Andrew.Murray@arm.com>
> Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
> ---
>  drivers/pci/setup-irq.c |   15 +++++++++++++++
>  include/linux/pci.h     |    3 +++
>  2 files changed, 18 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/pci/setup-irq.c b/drivers/pci/setup-irq.c
> index eb219a1..ea91874 100644
> --- a/drivers/pci/setup-irq.c
> +++ b/drivers/pci/setup-irq.c
> @@ -62,3 +62,18 @@ pci_fixup_irqs(u8 (*swizzle)(struct pci_dev *, u8 *),
>         for_each_pci_dev(dev)
>                 pdev_fixup_irq(dev, swizzle, map_irq);
>  }
> +
> +void __init
> +pci_bus_fixup_irqs(struct pci_bus *bus,
> +               u8 (*swizzle)(struct pci_dev *, u8 *),
> +               int (*map_irq)(const struct pci_dev *, u8, u8))
> +{
> +       struct pci_dev *dev;
> +
> +       list_for_each_entry(dev, &bus->devices, bus_list) {
> +               pdev_fixup_irq(dev, swizzle, map_irq);
> +
> +               if (dev->subordinate)
> +                       pci_bus_fixup_irqs(dev->subordinate, swizzle, map_irq);
> +       }
> +}
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 5faa831..1b3c2eb 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -953,6 +953,9 @@ void pdev_enable_device(struct pci_dev *);
>  int pci_enable_resources(struct pci_dev *, int mask);
>  void pci_fixup_irqs(u8 (*)(struct pci_dev *, u8 *),
>                     int (*)(const struct pci_dev *, u8, u8));
> +void pci_bus_fixup_irqs(struct pci_bus *bus,
> +               u8 (*swizzle)(struct pci_dev *, u8 *),
> +               int (*map_irq)(const struct pci_dev *, u8, u8));
>  #define HAVE_PCI_REQ_REGIONS   2
>  int __must_check pci_request_regions(struct pci_dev *, const char *);
>  int __must_check pci_request_regions_exclusive(struct pci_dev *, const char *);
> --
> 1.7.0.4
>
>
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