diff options
| author | Michael Ellerman <michael@ellerman.id.au> | 2009-03-20 15:22:12 +1100 |
|---|---|---|
| committer | Jesse Barnes <jbarnes@virtuousgeek.org> | 2009-03-20 11:35:04 -0700 |
| commit | fafad5bf06c3a3bb8b24b28b6f065367e7411872 (patch) | |
| tree | 32f88260a757d9e24e913202fddcd2cdd420eb03 /Documentation/PCI/MSI-HOWTO.txt | |
| parent | 5546d6f56807115a035d140f7364ce5807dbcc87 (diff) | |
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>
Diffstat (limited to 'Documentation/PCI/MSI-HOWTO.txt')
| -rw-r--r-- | Documentation/PCI/MSI-HOWTO.txt | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt index 9494f6dc38eb..dcf7acc720e1 100644 --- a/Documentation/PCI/MSI-HOWTO.txt +++ b/Documentation/PCI/MSI-HOWTO.txt @@ -176,7 +176,8 @@ request_irq() for each 'vector' that it decides to use. If this function returns a negative number, it indicates an error and the driver should not attempt to allocate any more MSI-X interrupts for this device. If it returns a positive number, it indicates the maximum -number of interrupt vectors that could have been allocated. +number of interrupt vectors that could have been allocated. See example +below. This function, in contrast with pci_enable_msi(), does not adjust dev->irq. The device will not generate interrupts for this interrupt @@ -187,6 +188,26 @@ free them again later. Device drivers should normally call this function once per device during the initialization phase. +It is ideal if drivers can cope with a variable number of MSI-X interrupts, +there are many reasons why the platform may not be able to provide the +exact number a driver asks for. + +A request loop to achieve that might look like: + +static int foo_driver_enable_msix(struct foo_adapter *adapter, int nvec) +{ + while (nvec >= FOO_DRIVER_MINIMUM_NVEC) { + rc = pci_enable_msix(adapter->pdev, + adapter->msix_entries, nvec); + if (rc > 0) + nvec = rc; + else + return rc; + } + + return -ENOSPC; +} + 4.3.2 pci_disable_msix void pci_disable_msix(struct pci_dev *dev) |