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

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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>
This commit is contained in:
Michael Ellerman 2009-02-11 22:27:02 +11:00 committed by Jesse Barnes
parent 35e1801ea6
commit b5fbf53324
1 changed files with 12 additions and 9 deletions
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21
drivers/pci/msi.c
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@ -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;