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PCI/MSI: Enable multiple MSIs with pci_enable_msi_block_auto()

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The new function pci_enable_msi_block_auto() tries to allocate
maximum possible number of MSIs up to the number the device
supports. It generalizes a pattern when pci_enable_msi_block()
is contiguously called until it succeeds or fails.

Opposite to pci_enable_msi_block() which takes the number of
MSIs to allocate as a input parameter,
pci_enable_msi_block_auto() could be used by device drivers to
obtain the number of assigned MSIs and the number of MSIs the
device supports.

Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Jeff Garzik <jgarzik@pobox.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/c3de2419df94a0f95ca1a6f755afc421486455e6.1353324359.git.agordeev@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Alexander Gordeev
2012-11-19 16:02:10 +01:00
committed by Ingo Molnar
parent 51906e779f
commit 08261d87f7
3 changed files with 65 additions and 5 deletions
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26
drivers/pci/msi.c
View File

@@ -845,6 +845,32 @@ int pci_enable_msi_block(struct pci_dev *dev, unsigned int nvec)
}
EXPORT_SYMBOL(pci_enable_msi_block);
int pci_enable_msi_block_auto(struct pci_dev *dev, unsigned int *maxvec)
{
int ret, pos, nvec;
u16 msgctl;
pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
if (!pos)
return -EINVAL;
pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &msgctl);
ret = 1 << ((msgctl & PCI_MSI_FLAGS_QMASK) >> 1);
if (maxvec)
*maxvec = ret;
do {
nvec = ret;
ret = pci_enable_msi_block(dev, nvec);
} while (ret > 0);
if (ret < 0)
return ret;
return nvec;
}
EXPORT_SYMBOL(pci_enable_msi_block_auto);
void pci_msi_shutdown(struct pci_dev *dev)
{
struct msi_desc *desc;