On Tue, Feb 02, 2021 at 01:40:18PM +0100, Gustavo Pimentel wrote:

 /**
+ * pci_find_vsec_capability - Find a vendor-specific extended capability
+ * @dev: PCI device to query
+ * @cap: vendor-specific capability ID code
+ *
+ * Returns the address of the vendor-specific structure that matches the
+ * requested capability ID code within the device's PCI configuration space
+ * or 0 if it does not find a match.
+ */
+u16 pci_find_vsec_capability(struct pci_dev *dev, int vsec_cap_id)
+{

As the name implies, the capability is "vendor-specific", so it is perfectly
possible that two vendors use the same VSEC ID for different things.

To make sure you're looking for the right capability, you need to pass
a u16 vendor into this function and bail out if dev->vendor is different.

+	u16 vsec;
+	u32 header;
+
+	vsec = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_VNDR);
+	while (vsec) {
+		if (pci_read_config_dword(dev, vsec + PCI_VSEC_HDR,
+					  &header) == PCIBIOS_SUCCESSFUL &&
+		    PCI_VSEC_CAP_ID(header) == vsec_cap_id)
+			return vsec;
+
+		vsec = pci_find_next_ext_capability(dev, vsec,
+						    PCI_EXT_CAP_ID_VNDR);
+	}

FWIW, a more succinct implementation would be:

	while ((vsec = pci_find_next_ext_capability(...))) { ... }

See set_pcie_thunderbolt() in drivers/pci/probe.c for an example.
Please consider refactoring that function to use your new helper.

Thanks,

Lukas