On Thu, Jun 23, 2016 at 01:16:10PM +0200, Alexander Gordeev wrote:
> New APIs should be documented in Documentation/PCI/MSI-HOWTO.txt, I guess.
Ok, done.
> > +static unsigned int pci_nr_irq_vectors(struct pci_dev *pdev)
> > +{
> > + int nr_entries;
> > +
> > + nr_entries = pci_msix_vec_count(pdev);
> > + if (nr_entries <= 0 && pci_msi_supported(pdev, 1))
> > + nr_entries = pci_msi_vec_count(pdev);
> > + if (nr_entries <= 0)
> > + nr_entries = 1;
> > + return nr_entries;
> > +}
>
> This function is strange, because it:
> (a) does not consider PCI_IRQ_NOMSIX flag;
> (b) only calls pci_msi_supported() for MSI case;
> (c) calls pci_msi_supported() with just one vector;
> (d) might return suboptimal number of vectors (number of MSI-X used
> later for MSI or vice versa)
>
> Overall, I would suggest simply return maximum between MSI-X and MSI
> numbers and let the rest of the code (i.e the two range functions)
> handle a-d.
Ok, fixed except for (c) - the only thing pci_msi_supported does with
nvec is to check for it being less than 1, which we don't care about,
and which really shouldn't be in this function to start with.
> > + struct msix_entry *msix_entries;
> > + int vecs, i;
> > +
> > + msix_entries = kcalloc(max_vecs, sizeof(struct msix_entry), GFP_KERNEL);
> > + if (!msix_entries)
> > + return -ENOMEM;
> > +
> > + for (i = 0; i < max_vecs; i++)
> > + msix_entries[i].entry = i;
> > +
> > + vecs = pci_enable_msix_range(pdev, msix_entries, min_vecs, max_vecs);
> > + if (vecs > 0) {
>
> This condition check is unneeded.
Why? We could get -ENOSPC back. Oh, because our for loop will
terminate immediately. I can update it, but I think removing it
is less readable than keeping it around.
> > + if (!(flags & PCI_IRQ_NOMSIX)) {
> > + vecs = pci_enable_msix_range_wrapper(dev, irqs, min_vecs,
> > + max_vecs);
> > + if (vecs > 0)
> > + goto done;
> > + }
> > +
> > + vecs = pci_enable_msi_range(dev, min_vecs, max_vecs);
> > + if (vecs > 0) {
> > + for (i = 0; i < vecs; i++)
> > + irqs[i] = dev->irq + i;
> > + goto done;
> > + }
> > +
> > + if (min_vecs > 1)
> > + return -ENOSPC;
>
> irqs is leaked if (min_vecs > 1)
>
> You can get rid of this check at all if you reorganize your code i.e.
> like this:
>
> ...
>
> vecs = pci_enable_msi_range(dev, min_vecs, max_vecs);
> if (vecs < 0)
> goto legacy;
>
> for (i = 0; i < vecs; i++)
> irqs[i] = dev->irq + i;
>
> done:
> ...
>
>
> legacy:
> ...
I've just moved the if below the kfree.
> > +void pci_free_irq_vectors(struct pci_dev *dev)
> > +{
> > + if (dev->msix_enabled)
> > + pci_disable_msix(dev);
> > + else if (dev->msi_enabled)
> > + pci_disable_msi(dev);
>
> The checks are probably redundant or incomplete. Redundant - because
> pci_disable_msi()/pci_disable_msix() do it anyways:
>
> if (!pci_msi_enable || !dev || !dev->msi_enabled)
> return;
>
> Incomplete - because the two other conditions are not checked.
Ok, I've dropped the check.
>
> > + if (dev->irqs != &dev->irq)
> > + kfree(dev->irqs);
>
> Unset dev->irqs?
Fine with me, added.
> > +#define PCI_IRQ_NOMSIX (1 << 0) /* don't try to use MSI-X interrupts */
>
> BTW, why PCI_IRQ_NOMSIX only and no PCI_IRQ_NOMSI?
Because there is no need to call this API if your device only supports
a single legacy vector anyway.
> > + if (min_vecs > 1)
> > + return -ENOSPC;
> > + dev->irqs = &dev->irq;
> > + return 1;
> > +}
> > +static inline void pci_free_irq_vectors(struct pci_dev *dev)
> > +{
>
> Unset dev->irqs?
Ok.
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