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Subject[PATCH 10/9] PCI/MSI: Undeprecate pci_enable_msi()
Signed-off-by: Alexander Gordeev <>
Documentation/PCI/MSI-HOWTO.txt | 23 ++++++++++++++++++++---
1 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt
index a8d0100..3c3080e 100644
--- a/Documentation/PCI/MSI-HOWTO.txt
+++ b/Documentation/PCI/MSI-HOWTO.txt
@@ -82,7 +82,19 @@ Most of the hard work is done for the driver in the PCI layer. It simply
has to request that the PCI layer set up the MSI capability for this

-4.2.1 pci_enable_msi_range
+4.2.1 pci_enable_msi
+int pci_enable_msi(struct pci_dev *dev)
+A successful call allocates ONE interrupt to the device, regardless
+of how many MSIs the device supports. The device is switched from
+pin-based interrupt mode to MSI mode. The dev->irq number is changed
+to a new number which represents the message signaled interrupt;
+consequently, this function should be called before the driver calls
+request_irq(), because an MSI is delivered via a vector that is
+different from the vector of a pin-based interrupt.
+4.2.2 pci_enable_msi_range

int pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec)

@@ -158,7 +170,12 @@ static int foo_driver_enable_single_msi(struct pci_dev *pdev)
return pci_enable_msi_range(pdev, 1, 1);

-4.2.2 pci_disable_msi
+Note, unlike pci_enable_msi() function, which could be also used to
+enable the single MSI mode, pci_enable_msi_range() returns either a
+negative errno or 1 (not negative errno or 0 - as pci_enable_msi()
+4.2.3 pci_disable_msi

void pci_disable_msi(struct pci_dev *dev)

@@ -172,7 +189,7 @@ 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.

-4.2.3 pci_msi_vec_count
+4.2.4 pci_msi_vec_count

int pci_msi_vec_count(struct pci_dev *dev)

Alexander Gordeev

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