since enabling MSIs disables the pin-based IRQ and the driver will not
receive interrupts on the old interrupt.
-4.2.2 pci_disable_msi
+4.2.2 pci_enable_msi_block
+
+int pci_enable_msi_block(struct pci_dev *dev, int count)
+
+This variation on the above call allows a device driver to request multiple
+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 0, it has succeeded in allocating at least as many
+interrupts as the driver requested (it may have allocated more in order
+to satisfy the power-of-two requirement). 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 + count - 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 this function returns a positive number, it will be
+less than 'count' and indicate the number of interrupts that could have
+been allocated. In neither case will the irq value have been
+updated, nor will the device have been switched into MSI mode.
+
+The device driver must decide what action to take if
+pci_enable_msi_block() returns a value less than the number asked for.
+Some devices can make use of fewer interrupts than the maximum they
+request; in this case the driver should call pci_enable_msi_block()
+again. Note that it is not guaranteed to succeed, even when the
+'count' has been reduced to the value returned from a previous call to
+pci_enable_msi_block(). This is because there are multiple constraints
+on the number of vectors that can be allocated; pci_enable_msi_block()
+will return as soon as it finds any constraint that doesn't allow the
+call to succeed.
+
+4.2.3 pci_disable_msi
void pci_disable_msi(struct pci_dev *dev)
-This function should be used to undo the effect of pci_enable_msi().
-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.
+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.
A device driver must always call free_irq() on the interrupt(s)
for which it has called request_irq() before calling this function.
If this function returns a negative number, it indicates an error and
the driver should not attempt to allocate any more MSI-X interrupts for
this device. If it returns a positive number, it indicates the maximum
-number of interrupt vectors that could have been allocated.
+number of interrupt vectors that could have been allocated. See example
+below.
This function, in contrast with pci_enable_msi(), does not adjust
dev->irq. The device will not generate interrupts for this interrupt
Device drivers should normally call this function once per device
during the initialization phase.
+It is ideal if drivers can cope with a variable number of MSI-X interrupts,
+there are many reasons why the platform may not be able to provide the
+exact number a driver asks for.
+
+A request loop to achieve that might look like:
+
+static int foo_driver_enable_msix(struct foo_adapter *adapter, int nvec)
+{
+ while (nvec >= FOO_DRIVER_MINIMUM_NVEC) {
+ rc = pci_enable_msix(adapter->pdev,
+ adapter->msix_entries, nvec);
+ if (rc > 0)
+ nvec = rc;
+ else
+ return rc;
+ }
+
+ return -ENOSPC;
+}
+
4.3.2 pci_disable_msix
void pci_disable_msix(struct pci_dev *dev)
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