path: root/Documentation/PCI/MSI-HOWTO.txt
diff options
authorAlexander Gordeev <agordeev@redhat.com>2012-11-19 16:02:10 +0100
committerIngo Molnar <mingo@kernel.org>2013-01-24 17:25:13 +0100
commit08261d87f7d1b6253ab3223756625a5c74532293 (patch)
treec0025a8e4593564bf356f1f185c21a137a96cb8a /Documentation/PCI/MSI-HOWTO.txt
parent51906e779f2b13b38f8153774c4c7163d412ffd9 (diff)
PCI/MSI: Enable multiple MSIs with pci_enable_msi_block_auto()
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>
Diffstat (limited to 'Documentation/PCI/MSI-HOWTO.txt')
1 files changed, 32 insertions, 5 deletions
diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt
index 53e6fca146d7..a09178086c30 100644
--- a/Documentation/PCI/MSI-HOWTO.txt
+++ b/Documentation/PCI/MSI-HOWTO.txt
@@ -127,15 +127,42 @@ on the number of vectors that can be allocated; pci_enable_msi_block()
returns as soon as it finds any constraint that doesn't allow the
call to succeed.
-4.2.3 pci_disable_msi
+4.2.3 pci_enable_msi_block_auto
+int pci_enable_msi_block_auto(struct pci_dev *dev, unsigned int *count)
+This variation on pci_enable_msi() call allows a device driver to request
+the maximum possible number of MSIs. The MSI specification only allows
+interrupts to be allocated in powers of two, up to a maximum of 2^5 (32).
+If this function returns a positive number, it indicates that it has
+succeeded and the returned value is the number of allocated interrupts. In
+this case, the function enables MSI on this device and updates dev->irq to
+be the lowest of the new interrupts assigned to it. The other interrupts
+assigned to the device are in the range dev->irq to dev->irq + returned
+value - 1.
+If this function returns a negative number, it indicates an error and
+the driver should not attempt to request any more MSI interrupts for
+this device.
+If the device driver needs to know the number of interrupts the device
+supports it can pass the pointer count where that number is stored. The
+device driver must decide what action to take if pci_enable_msi_block_auto()
+succeeds, but returns a value less than the number of interrupts supported.
+If the device driver does not need to know the number of interrupts
+supported, it can set the pointer count to NULL.
+4.2.4 pci_disable_msi
void pci_disable_msi(struct pci_dev *dev)
This function should be used to undo the effect of pci_enable_msi() or
-pci_enable_msi_block(). Calling it restores dev->irq to the pin-based
-interrupt number and frees the previously allocated message signaled
-interrupt(s). The interrupt may subsequently be assigned to another
-device, so drivers should not cache the value of dev->irq.
+pci_enable_msi_block() or pci_enable_msi_block_auto(). Calling it restores
+dev->irq to the pin-based interrupt number and frees the previously
+allocated message signaled interrupt(s). The interrupt may subsequently be
+assigned to another device, so drivers should not cache the value of
Before calling this function, a device driver must always call free_irq()
on any interrupt for which it previously called request_irq().

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