[PATCH v4 1/5] PCI: Add pci_bus_fixup_irqs().

Bjorn Helgaas
2015-10-07T23:08:47Z

[+cc Matthew]

On Wed, Oct 07, 2015 at 01:08:40PM -0700, David Daney wrote:
> On 10/07/2015 12:44 PM, Bjorn Helgaas wrote:
> >Hi David,
> >
> >On Fri, Oct 02, 2015 at 11:43:59AM -0700, David Daney wrote:
> >>From: David Daney <david.daney@cavium.com>
> >>
> >>pci_bus_fixup_irqs() works like pci_fixup_irqs(), except it only does
> >>the fixups for devices on the specified bus.
> >>
> >>Follow-on patch will use the new function.
> >>
> >>Signed-off-by: David Daney <david.daney@cavium.com>
> >>---
> >>No change from v2.
> >>
> >> drivers/pci/setup-irq.c | 30 ++++++++++++++++++++++++++++++
> >> include/linux/pci.h | 4 ++++
> >> 2 files changed, 34 insertions(+)
> >>
> >>diff --git a/drivers/pci/setup-irq.c b/drivers/pci/setup-irq.c
> >>index 95c225b..189ad17 100644
> >>--- a/drivers/pci/setup-irq.c
> >>+++ b/drivers/pci/setup-irq.c
> >>@@ -66,3 +66,33 @@ void pci_fixup_irqs(u8 (*swizzle)(struct pci_dev *, u8 *),
> >> pdev_fixup_irq(dev, swizzle, map_irq);
> >> }
> >> EXPORT_SYMBOL_GPL(pci_fixup_irqs);
> >>+
> >>+struct pci_bus_fixup_cb_info {
> >>+ u8 (*swizzle)(struct pci_dev *, u8 *);
> >>+ int (*map_irq)(const struct pci_dev *, u8, u8);
> >>+};
> >>+
> >>+static int pci_bus_fixup_irq_cb(struct pci_dev *dev, void *arg)
> >>+{
> >>+ struct pci_bus_fixup_cb_info *info = arg;
> >>+
> >>+ pdev_fixup_irq(dev, info->swizzle, info->map_irq);
> >>+ return 0;
> >>+}
> >>+
> >>+/*
> >>+ * Fixup the irqs only for devices on the given bus using supplied
> >>+ * swizzle and map_irq function pointers
> >>+ */
> >>+void 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_bus_fixup_cb_info info;
> >>+
> >>+ info.swizzle = swizzle;
> >>+ info.map_irq = map_irq;
> >>+ pci_walk_bus(bus, pci_bus_fixup_irq_cb, &info);
> >
> >I don't like the existing pci_fixup_irqs(), so by transitivity, I
> >don't like pci_bus_fixup_irqs() either.
>
> We are in agreement with respect to this point.
>
> > The problem is that in both
> >cases this is a one-time pass over the tree, so we don't handle
> >hot-added devices correctly.
> >
> >I think we need to get rid of pci_fixup_irqs() and somehow integrate
> >it into the pci_device_add() path, where it would be done once for
> >every device we enumerate.
>
> I also agree with this point.
>
> > If we did that, I don't think you would
> >need to add pci_bus_fixup_irqs(), would you?
>
> Nope.
>
> However, such a change is essentially untestable by me. So, I
> didn't attempt it. pci_fixup_irqs() is used by alpha, arm, m68k,
> mips, sh, sparc, tile, unicore32 and other things as well. If the
> core pci_device_add() code were to suddenly start doing the fixup,
> there would be the potential to break all these things I cannot
> test.

Yep, that's certainly a risk. I can't test all those arches either,
but I think it's a risk worth taking because the end result is more
maintainable.

Matthew Minter did some really nice work on this last year, but it got
stalled somehow. I wonder if we can resurrect it? It seems like it
was pretty close to being ready. Here's a pointer to the last posting
I saw:

http://lkml.kernel.org/r/1412222866-21068-1-git-send-email-matt at masarand.com

Bjorn