diff options
Diffstat (limited to 'drivers/pci/pci.c')
| -rw-r--r-- | drivers/pci/pci.c | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 5b548aee9cbc..77b493b3d97b 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -303,6 +303,49 @@ int pci_find_ext_capability(struct pci_dev *dev, int cap) } EXPORT_SYMBOL_GPL(pci_find_ext_capability); +/** + * pci_bus_find_ext_capability - find an extended capability + * @bus: the PCI bus to query + * @devfn: PCI device to query + * @cap: capability code + * + * Like pci_find_ext_capability() but works for pci devices that do not have a + * pci_dev structure set up yet. + * + * Returns the address of the requested capability structure within the + * device's PCI configuration space or 0 in case the device does not + * support it. + */ +int pci_bus_find_ext_capability(struct pci_bus *bus, unsigned int devfn, + int cap) +{ + u32 header; + int ttl; + int pos = PCI_CFG_SPACE_SIZE; + + /* minimum 8 bytes per capability */ + ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8; + + if (!pci_bus_read_config_dword(bus, devfn, pos, &header)) + return 0; + if (header == 0xffffffff || header == 0) + return 0; + + while (ttl-- > 0) { + if (PCI_EXT_CAP_ID(header) == cap) + return pos; + + pos = PCI_EXT_CAP_NEXT(header); + if (pos < PCI_CFG_SPACE_SIZE) + break; + + if (!pci_bus_read_config_dword(bus, devfn, pos, &header)) + break; + } + + return 0; +} + static int __pci_find_next_ht_cap(struct pci_dev *dev, int pos, int ht_cap) { int rc, ttl = PCI_FIND_CAP_TTL; |