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?
> --
> 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++) {
>
--
MST
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