* Alexander Gordeev <agordeev@xxxxxxxxxx> wrote: > When multiple MSIs are enabled with pci_enable_msi_block(), the > requested number of interrupts 'nvec' is rounded up to the nearest > power-of-two value. The result is then used for setting up the > number of MSI messages in the PCI device and allocation of > interrupt resources in the operating system (i.e. vector numbers). > Thus, in cases when a device driver requests some number of MSIs > and this number is not a power-of-two value, the extra operating > system resources (allocated as the result of rounding) are wasted. > > This fix introduces 'msi_desc::nvec' field to address the above > issue. When non-zero, it will report the actual number of MSIs the > device will send, as requested by the device driver. This value > should be used by architectures to properly set up and tear down > associated interrupt resources. > > Note, although the existing 'msi_desc::multiple' field might seem > redundant, in fact in does not. In general case the number of MSIs a > PCI device is initialized with is not necessarily the closest power- > of-two value of the number of MSIs the device will send. Thus, in > theory it would not be always possible to derive the former from the > latter and we need to keep them both, to stress this corner case. > Besides, since 'msi_desc::multiple' is a bitfield, throwing it out > would not save us any space. > > Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxx> Would be nice to have an Acked-by from Bjorn for this patch. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
