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PCI MSI: Add example request loop to MSI-HOWTO.txt
Encourage driver writers to think about supporting a variable number of MSI-X interrupts, and give an example of how to do such a request. Acked-by: Matthew Wilcox <willy@linux.intel.com> Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
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@ -176,7 +176,8 @@ request_irq() for each 'vector' that it decides to use.
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If this function returns a negative number, it indicates an error and
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the driver should not attempt to allocate any more MSI-X interrupts for
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this device. If it returns a positive number, it indicates the maximum
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number of interrupt vectors that could have been allocated.
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number of interrupt vectors that could have been allocated. See example
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below.
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This function, in contrast with pci_enable_msi(), does not adjust
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dev->irq. The device will not generate interrupts for this interrupt
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@ -187,6 +188,26 @@ free them again later.
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Device drivers should normally call this function once per device
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during the initialization phase.
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It is ideal if drivers can cope with a variable number of MSI-X interrupts,
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there are many reasons why the platform may not be able to provide the
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exact number a driver asks for.
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A request loop to achieve that might look like:
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static int foo_driver_enable_msix(struct foo_adapter *adapter, int nvec)
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{
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while (nvec >= FOO_DRIVER_MINIMUM_NVEC) {
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rc = pci_enable_msix(adapter->pdev,
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adapter->msix_entries, nvec);
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if (rc > 0)
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nvec = rc;
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else
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return rc;
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}
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return -ENOSPC;
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}
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4.3.2 pci_disable_msix
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void pci_disable_msix(struct pci_dev *dev)
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