diff options
| author | Christoph Hellwig <hch@lst.de> | 2017-02-15 10:58:22 +0300 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2017-02-15 19:32:57 +0300 |
| commit | c3cf2c61ddc1410424da0ea87717edf16fc296c5 (patch) | |
| tree | fe2a895e44148f40772eb392ff94a64e62e0469e /Documentation | |
| parent | 948b7620c15411444167a62cfc14cdd4b0e44682 (diff) | |
| download | linux-c3cf2c61ddc1410424da0ea87717edf16fc296c5.tar.xz | |
PCI/MSI: Document pci_alloc_irq_vectors(), deprecate pci_enable_msi()
Document pci_alloc_irq_vectors() instead of the deprecated pci_enable_msi()
and pci_enable_msix() APIs.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/PCI/pci.txt | 24 |
1 files changed, 12 insertions, 12 deletions
diff --git a/Documentation/PCI/pci.txt b/Documentation/PCI/pci.txt index 77f49dc5be23..611a75e4366e 100644 --- a/Documentation/PCI/pci.txt +++ b/Documentation/PCI/pci.txt @@ -382,18 +382,18 @@ The fundamental difference between MSI and MSI-X is how multiple "vectors" get allocated. MSI requires contiguous blocks of vectors while MSI-X can allocate several individual ones. -MSI capability can be enabled by calling pci_enable_msi() or -pci_enable_msix() before calling request_irq(). This causes -the PCI support to program CPU vector data into the PCI device -capability registers. - -If your PCI device supports both, try to enable MSI-X first. -Only one can be enabled at a time. Many architectures, chip-sets, -or BIOSes do NOT support MSI or MSI-X and the call to pci_enable_msi/msix -will fail. This is important to note since many drivers have -two (or more) interrupt handlers: one for MSI/MSI-X and another for IRQs. -They choose which handler to register with request_irq() based on the -return value from pci_enable_msi/msix(). +MSI capability can be enabled by calling pci_alloc_irq_vectors() with the +PCI_IRQ_MSI and/or PCI_IRQ_MSIX flags before calling request_irq(). This +causes the PCI support to program CPU vector data into the PCI device +capability registers. Many architectures, chip-sets, or BIOSes do NOT +support MSI or MSI-X and a call to pci_alloc_irq_vectors with just +the PCI_IRQ_MSI and PCI_IRQ_MSIX flags will fail, so try to always +specify PCI_IRQ_LEGACY as well. + +Drivers that have different interrupt handlers for MSI/MSI-X and +legacy INTx should chose the right one based on the msi_enabled +and msix_enabled flags in the pci_dev structure after calling +pci_alloc_irq_vectors. There are (at least) two really good reasons for using MSI: 1) MSI is an exclusive interrupt vector by definition. |