Messages in this thread | | | Date | Thu, 26 Sep 2013 12:45:48 +0200 | From | Alexander Gordeev <> | Subject | Re: [PATCH v2 2/6] PCI/MSI: Factor out pci_get_msi_cap() interface |
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On Thu, Sep 26, 2013 at 09:58:53AM +0100, David Laight wrote: > Would it be possible to do some kind of 2-stage allocation. > In the first pass the driver would pass a minimum and desired > number of MSI-X interrupts, but not actually be given any.
Repeated calls to msi_enable_msi/msix() is what we are trying to avoid.
> Interrupts could then be allocated after it is known how many > are required and how many are available.
Yep, that what we are heading to. So basic pattern I see would be like this:
int foo_driver_enable_msix(struct pci_dev *pdev, int nvec) { ...
rc = pci_msix_table_size(pdev); if (rc < 0) return rc;
nvec = min(nvec, rc); if (nvec < FOO_DRIVER_MINIMUM_NVEC) goto single_msi;
for (i = 0; i < nvec; i++) entries[i].entry = i;
rc = pci_enable_msix(pdev, entries, nvec); if (rc) goto single_msi;
return 0;
single_msi: ...
}
But this will break pSeries and we might end up with something like this:
int foo_driver_enable_msix(struct pci_dev *pdev, int nvec) { ...
rc = pci_msix_table_size(pdev); if (rc < 0) return rc;
nvec = min(nvec, rc); if (nvec < FOO_DRIVER_MINIMUM_NVEC) goto single_msi;
rc = pci_get_msix_limit(pdev, nvec); if (rc < 0) return rc;
nvec = min(nvec, rc); if (nvec < FOO_DRIVER_MINIMUM_NVEC) goto single_msi;
for (i = 0; i < nvec; i++) entries[i].entry = i;
rc = pci_enable_msix(pdev, entries, nvec); if (rc) goto single_msi;
return 0;
single_msi: ...
}
> David
-- Regards, Alexander Gordeev agordeev@redhat.com
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