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authorChristoph Hellwig <hch@lst.de>2016-08-11 17:11:04 +0300
committerBjorn Helgaas <bhelgaas@google.com>2016-08-16 22:07:30 +0300
commit4fe0d154880bb6eb833cbe84fa6f385f400f0b9c (patch)
tree3836c67795f4046fbeb20a8fd89a185b3ae82ee4 /Documentation/PCI/MSI-HOWTO.txt
parent8b078c603249239f597dc395ac182667c8e0af9c (diff)
downloadlinux-4fe0d154880bb6eb833cbe84fa6f385f400f0b9c.tar.xz
PCI: Use positive flags in pci_alloc_irq_vectors()
Instead of passing negative flags like PCI_IRQ_NOMSI to prevent use of certain interrupt types, pass positive flags like PCI_IRQ_LEGACY, PCI_IRQ_MSI, etc., to specify the acceptable interrupt types. This is based on a number of pending driver conversions that just happend to be a whole more obvious to read this way, and given that we have no users in the tree yet it can still easily be done. I've also added a PCI_IRQ_ALL_TYPES catchall to keep the case of accepting all interrupt types very simple. [bhelgaas: changelog, fix PCI_IRQ_AFFINITY doc typo, remove mention of PCI_IRQ_NOLEGACY] Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Alexander Gordeev <agordeev@redhat.com>
Diffstat (limited to 'Documentation/PCI/MSI-HOWTO.txt')
-rw-r--r--Documentation/PCI/MSI-HOWTO.txt24
1 files changed, 10 insertions, 14 deletions
diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt
index c55df2911136..cd9c9f6a7cd9 100644
--- a/Documentation/PCI/MSI-HOWTO.txt
+++ b/Documentation/PCI/MSI-HOWTO.txt
@@ -94,14 +94,11 @@ has a requirements for a minimum number of vectors the driver can pass a
min_vecs argument set to this limit, and the PCI core will return -ENOSPC
if it can't meet the minimum number of vectors.
-The flags argument should normally be set to 0, but can be used to pass the
-PCI_IRQ_NOMSI and PCI_IRQ_NOMSIX flag in case a device claims to support
-MSI or MSI-X, but the support is broken, or to pass PCI_IRQ_NOLEGACY in
-case the device does not support legacy interrupt lines.
-
-By default this function will spread the interrupts around the available
-CPUs, but this feature can be disabled by passing the PCI_IRQ_NOAFFINITY
-flag.
+The flags argument is used to specify which type of interrupt can be used
+by the device and the driver (PCI_IRQ_LEGACY, PCI_IRQ_MSI, PCI_IRQ_MSIX).
+A convenient short-hand (PCI_IRQ_ALL_TYPES) is also available to ask for
+any possible kind of interrupt. If the PCI_IRQ_AFFINITY flag is set,
+pci_alloc_irq_vectors() will spread the interrupts around the available CPUs.
To get the Linux IRQ numbers passed to request_irq() and free_irq() and the
vectors, use the following function:
@@ -131,7 +128,7 @@ larger than the number supported by the device it will automatically be
capped to the supported limit, so there is no need to query the number of
vectors supported beforehand:
- nvec = pci_alloc_irq_vectors(pdev, 1, nvec, 0);
+ nvec = pci_alloc_irq_vectors(pdev, 1, nvec, PCI_IRQ_ALL_TYPES)
if (nvec < 0)
goto out_err;
@@ -140,7 +137,7 @@ interrupts it can request a particular number of interrupts by passing that
number to pci_alloc_irq_vectors() function as both 'min_vecs' and
'max_vecs' parameters:
- ret = pci_alloc_irq_vectors(pdev, nvec, nvec, 0);
+ ret = pci_alloc_irq_vectors(pdev, nvec, nvec, PCI_IRQ_ALL_TYPES);
if (ret < 0)
goto out_err;
@@ -148,15 +145,14 @@ The most notorious example of the request type described above is enabling
the single MSI mode for a device. It could be done by passing two 1s as
'min_vecs' and 'max_vecs':
- ret = pci_alloc_irq_vectors(pdev, 1, 1, 0);
+ ret = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_ALL_TYPES);
if (ret < 0)
goto out_err;
Some devices might not support using legacy line interrupts, in which case
-the PCI_IRQ_NOLEGACY flag can be used to fail the request if the platform
-can't provide MSI or MSI-X interrupts:
+the driver can specify that only MSI or MSI-X is acceptable:
- nvec = pci_alloc_irq_vectors(pdev, 1, nvec, PCI_IRQ_NOLEGACY);
+ nvec = pci_alloc_irq_vectors(pdev, 1, nvec, PCI_IRQ_MSI | PCI_IRQ_MSIX);
if (nvec < 0)
goto out_err;