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| author | Alexander Gordeev <agordeev@redhat.com> | 2013-12-30 08:28:13 +0100 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2014-01-04 01:17:55 +0100 |
| commit | d1ac1d2622e8f0fd2a25127a8649d135b54db8a9 (patch) | |
| tree | 9b267fa3c5d97fc9c6c65877a9d493d407258abe /Documentation/PCI | |
| parent | PCI/MSI: Make pci_enable_msi/msix() 'nvec' argument type as int (diff) | |
| download | linux-d1ac1d2622e8f0fd2a25127a8649d135b54db8a9.tar.xz linux-d1ac1d2622e8f0fd2a25127a8649d135b54db8a9.zip | |
PCI/MSI: Add pci_msi_vec_count()
Device drivers can use this interface to obtain the maximum number of MSI
interrupts the device supports and use that number, e.g., in a subsequent
call to pci_enable_msi_block().
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'Documentation/PCI')
| -rw-r--r-- | Documentation/PCI/MSI-HOWTO.txt | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt index a4d174e95413..a8b41788dfde 100644 --- a/Documentation/PCI/MSI-HOWTO.txt +++ b/Documentation/PCI/MSI-HOWTO.txt @@ -169,6 +169,21 @@ on any interrupt for which it previously called request_irq(). Failure to do so results in a BUG_ON(), leaving the device with MSI enabled and thus leaking its vector. +4.2.5 pci_msi_vec_count + +int pci_msi_vec_count(struct pci_dev *dev) + +This function could be used to retrieve the number of MSI vectors the +device requested (via the Multiple Message Capable register). The MSI +specification only allows the returned value to be a power of two, +up to a maximum of 2^5 (32). + +If this function returns a negative number, it indicates the device is +not capable of sending MSIs. + +If this function returns a positive number, it indicates the maximum +number of MSI interrupt vectors that could be allocated. + 4.3 Using MSI-X The MSI-X capability is much more flexible than the MSI capability. |