On Tue, Nov 08, 2016 at 10:48:32AM -0500, Peter Xu wrote:
> On Tue, Nov 08, 2016 at 01:27:31PM +0100, Alexander Gordeev wrote:
> > On Fri, Nov 04, 2016 at 05:41:01PM +0100, Andrew Jones wrote:
> > > > /* Scan bus look for a specific device. Only bus 0 scanned for now. */
> > > > -pcidevaddr_t pci_find_dev(uint16_t vendor_id, uint16_t device_id)
> > > > +int pci_find_dev(struct pci_dev *pci_dev, uint16_t vendor_id, uint16_t device_id)
> > > > {
> > > > pcidevaddr_t dev;
> > > >
> > > > - for (dev = 0; dev < 256; ++dev) {
> > > > + for (dev = 0; dev < PCI_DEVFN_MAX; ++dev) {
> > >
> > > Why introduce this PCI_DEVFN_MAX define?
> > >
> > > > if (pci_config_readw(dev, PCI_VENDOR_ID) == vendor_id &&
> > > > - pci_config_readw(dev, PCI_DEVICE_ID) == device_id)
> > > > - return dev;
> > > > + pci_config_readw(dev, PCI_DEVICE_ID) == device_id) {
> > > > + pci_dev_init(pci_dev, dev);
> > > > + return 0;
> > > > + }
> > > > }
> > > >
> > > > - return PCIDEVADDR_INVALID;
> > > > + return -1;
> > >
> > > Why not use bool for the ret type; true=good, false=bad?
> >
> > Both ways look strange to me. I would leave pci_find_dev() as is (low-
> > level) and move pci_dev_init() outside - so a usage would be i.e.:
> >
> > dev = pci_find_dev(PCI_VENDOR_ID_REDHAT, PCI_DEVICE_ID_REDHAT_TEST);
> > if (dev == PCIDEVADDR_INVALID)
> > ...
> > pci_dev_init(&pci_dev, dev);
>
> IMHO actually it'll be nicer with:
>
> struct pci_dev *pci_find_dev(uint16_t vendor_id, uint16_t device_id);
Yes, I was going to suggest this too, but then...
>
> But this needs dynamic allocation of memory, which might be an
> overkill for kvm-unit-test. So I chose to allocate the pci_dev on
> caller stack.
...saw the value of avoiding the alloc. That said, we do have precedent
for allocating in lib/* code already (virtio_bind), and I am currently
reworking x86's memory management code in order to enable malloc/calloc
use within lib code for x86. So we could go the alloc way as well...
>
> Anyway, I take the interface issue as a matter of taste.
Not quite. I see Alex's reasoning. Perhaps users want to simply query
if a device is there (pci_find_dev), but not actually init a pci_dev
struct each time they call it. Alex's proposal keeps pci_find_dev more
generally useful.
Thanks,
drew
>
> How about I take Drew's suggestion here with true/false? Then if we
> have any better idea with solid reasons, we can post seperate patch
> for it.
>
> Thanks,
>
> -- peterx
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