Re: Musings on MSI

[David Young <dyoung%pobox.com@localhost>]

On Wed, Aug 17, 2011 at 11:52:18AM -0700, Matt Thomas wrote:
> On Aug 17, 2011, at 9:35 AM, David Young wrote:
> >> int pci_msi_type(pci_chipset_tag_t pc, pci_msi_handle_t msih);
> >> 
> >> return the type of msi allocated (PCI_CAP_MSI or PCI_CAP_MSIX).  In the 
> >> latter case MSI vectors may not be contiguous.
> > 
> > Does it matter to the driver whether or not the vectors are contiguous?
> > Presumably there are no gaps in the available msirq?
> 
> MSIX doesn't matter, MSI it does.

Can you give an example where a user of this API has to care whether the
vectors are contiguous or not?

> >> void pci_msi_disestablish(pci_chipset_tag_t pc, void *ih);
> >> 
> >> Disestablishes but does not free the MSI.
> > 
> > You mean, pci_msi_disestablish() does not free to the MSI handle's pool?
> > Why not?
> 
> It does.  But not to the system pool.   pci_msi_free does that.

Does pci_msi_free() give back "excess" msirqs to the system pool?  Can
you give an example of how/why it is used?

Dave

-- 
David Young             OJC Technologies
dyoung%ojctech.com@localhost      Urbana, IL * (217) 344-0444 x24