From 08261d87f7d1b6253ab3223756625a5c74532293 Mon Sep 17 00:00:00 2001 From: Alexander Gordeev Date: Mon, 19 Nov 2012 16:02:10 +0100 Subject: 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 Acked-by: Bjorn Helgaas Cc: Suresh Siddha Cc: Yinghai Lu Cc: Matthew Wilcox Cc: Jeff Garzik Cc: Linus Torvalds Cc: Andrew Morton Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/c3de2419df94a0f95ca1a6f755afc421486455e6.1353324359.git.agordeev@redhat.com Signed-off-by: Ingo Molnar --- Documentation/PCI/MSI-HOWTO.txt | 37 ++++++++++++++++++++++++++++++++----- 1 file changed, 32 insertions(+), 5 deletions(-) (limited to 'Documentation/PCI') 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 +dev->irq. Before calling this function, a device driver must always call free_irq() on any interrupt for which it previously called request_irq(). -- cgit v1.2.3