pciexp_device: Introduce pciexp_find_ext_vendor_cap()
Vendors can choose to add non-standard capabilities inside a
Vendor-Specific Extended Capability. These are identified by
the Extended Capability ID 0x0b.
Change-Id: Idd6dd0e98bd53b19077afdd4c402114578bec966
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66454
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
diff --git a/src/device/pciexp_device.c b/src/device/pciexp_device.c
index ea0ec1a..bc40125 100644
--- a/src/device/pciexp_device.c
+++ b/src/device/pciexp_device.c
@@ -55,6 +55,35 @@
return pciexp_get_ext_cap_offset(dev, cap, next_cap_offset);
}
+/*
+ * Search for a vendor-specific extended capability,
+ * with the vendor-specific ID `cap`.
+ *
+ * Returns the offset of the vendor-specific header,
+ * i.e. the offset of the extended capability + 4,
+ * or 0 if none is found.
+ *
+ * A new search is started with `offset == 0`.
+ * To continue a search, the prior return value
+ * should be passed as `offset`.
+ */
+unsigned int pciexp_find_ext_vendor_cap(const struct device *dev, unsigned int cap,
+ unsigned int offset)
+{
+ /* Reconstruct capability offset from vendor-specific header offset. */
+ if (offset >= 4)
+ offset -= 4;
+
+ for (;;) {
+ offset = pciexp_find_extended_cap(dev, PCI_EXT_CAP_ID_VNDR, offset);
+ if (!offset)
+ return 0;
+
+ const unsigned int vndr_cap = pci_read_config32(dev, offset + 4);
+ if ((vndr_cap & 0xffff) == cap)
+ return offset + 4;
+ }
+}
/*
* Re-train a PCIe link