Commit b5fbf533 authored Feb 11, 2009 by Michael Ellerman Committed by Jesse Barnes Mar 19, 2009

PCI/MSI: Allow arch code to return the number of MSI-X available



There is code in msix_capability_init() which, when the requested number
of MSI-X couldn't be allocated, calculates how many MSI-X /could/ be
allocated and returns that to the driver. That allows the driver to then
make a second request, with a number of MSIs that should succeed.

The current code requires the arch code to setup as many msi_descs as it
can, and then return to the generic code. On some platforms the arch
code may already know how many MSI-X it can allocate, before it sets up
any of the msi_descs.

So change the logic such that if the arch code returns a positive error
code, that is taken to be the number of MSI-X that could be allocated.
If the error code is negative we still calculate the number available
using the old method.

Because it's a little subtle, make sure the error return code from
arch_setup_msi_irq() is always negative. That way only implementations
of arch_setup_msi_irqs() need to be careful about returning a positive
error code.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

parent 35e1801e

drivers/pci/msi.c

+12 −9

Original line number	Diff line number	Diff line
		@@ -42,8 +42,10 @@ int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)

		list_for_each_entry(entry, &dev->msi_list, list) {
		ret = arch_setup_msi_irq(dev, entry);
		if (ret)
		if (ret < 0)
		return ret;
		if (ret > 0)
		return -ENOSPC;
		}

		return 0;
		@@ -487,7 +489,9 @@ static int msix_capability_init(struct pci_dev *dev,
		}

		ret = arch_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSIX);
		if (ret) {
		if (ret < 0) {
		/* If we had some success report the number of irqs
		* we succeeded in setting up. */
		int avail = 0;
		list_for_each_entry(entry, &dev->msi_list, list) {
		if (entry->irq != 0) {
		@@ -495,14 +499,13 @@ static int msix_capability_init(struct pci_dev *dev,
		}
		}

		msi_free_irqs(dev);
		if (avail != 0)
		ret = avail;
		}

		/* If we had some success report the number of irqs
		* we succeeded in setting up.
		*/
		if (avail == 0)
		avail = ret;
		return avail;
		if (ret) {
		msi_free_irqs(dev);
		return ret;
		}

		i = 0;

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