On Thursday 07 May 2009 17:05:06 Michael S. Tsirkin wrote:
> On Thu, May 07, 2009 at 04:51:24PM +0800, Sheng Yang wrote:
> > On Thursday 07 May 2009 16:28:41 Michael S. Tsirkin wrote:
> > > pci_enable_msix currently returns -EINVAL if you ask
> > > for more vectors than supported by the device, which would
> > > typically cause fallback to regular interrupts.
> > >
> > > It's better to return the table size, making the driver retry
> > > MSI-X with less vectors.
> >
> > Hi Michael
> >
> > I think driver should read from capability list to know how many vector
> > supported by this device before enable MSI-X for device, as
> > pci_msix_table_size() did...
>
> Drivers can do this, but it's more code. Since pci_enable_msix
> calls pci_msix_table_size already, let it do the work. Right?
If you don't know the vectors number before you enable MSI-X, how can you
setup vectors?
I don't think it's proper way to go.
--
regards
Yang, Sheng
>
> > --
> > regards
> > Yang, Sheng
> >
> > > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > > ---
> > >
> > > Hi Jesse,
> > > This came up when I was adding MSI-X support to virtio pci driver,
> > > which does not know the exact table size upfront.
> > > Could you consider this patch for 2.6.31 please?
> > >
> > >
> > > drivers/pci/msi.c | 6 +++---
> > > 1 files changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> > > index 6f2e629..f5bd1c9 100644
> > > --- a/drivers/pci/msi.c
> > > +++ b/drivers/pci/msi.c
> > > @@ -687,8 +687,8 @@ int pci_msix_table_size(struct pci_dev *dev)
> > > * indicates the successful configuration of MSI-X capability
> > > structure * with new allocated MSI-X irqs. A return of < 0 indicates a
> > > failure. * Or a return of > 0 indicates that driver request is
> > > exceeding the number - * of irqs available. Driver should use the
> > > returned value to re-send - * its request.
> > > + * of irqs or MSI-X vectors available. Driver should use the returned
> > > value to + * re-send its request.
> > > **/
> > > int pci_enable_msix(struct pci_dev* dev, struct msix_entry *entries,
> > > int nvec) {
> > > @@ -704,7 +704,7 @@ int pci_enable_msix(struct pci_dev* dev, struct
> > > msix_entry *entries, int nvec)
> > >
> > > nr_entries = pci_msix_table_size(dev);
> > > if (nvec > nr_entries)
> > > - return -EINVAL;
> > > + return nr_entries;
> > >
> > > /* Check for any invalid entries */
> > > for (i = 0; i < nvec; i++) {
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