From c22c314a322e2243983d2f356a5f0532b2d846a5 Mon Sep 17 00:00:00 2001
From: Daniel Schaefer <git@danielschaefer.me>
Date: Sun, 14 Oct 2018 22:47:53 +0200
Subject: [PATCH] libpci is now able to find a specific instance of a
 capability

---
 lib/caps.c     | 37 +++++++++++++++++++++++++++++++++++--
 lib/libpci.ver |  5 +++++
 lib/pci.h      |  2 ++
 3 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/lib/caps.c b/lib/caps.c
index 9a2e0a5..4f41589 100644
--- a/lib/caps.c
+++ b/lib/caps.c
@@ -103,12 +103,45 @@ pci_free_caps(struct pci_dev *d)
 
 struct pci_cap *
 pci_find_cap(struct pci_dev *d, unsigned int id, unsigned int type)
+{
+  return pci_find_cap_nr(d, id, type, NULL);
+}
+
+/**
+ * Finds a particular capability of a device
+ *
+ * To select one capability if there are more than one with the same id you
+ * can provide a pointer to an unsigned int that contains the index which you
+ * want as cap_number. If you don't care and are fine with the first one you
+ * can supply NULL. To cap_number the acutal number of capablities with that id
+ * will be written.
+ *
+ * @param d          Which device to target
+ * @param id         Capability ID
+ * @param type       PCI_FILL_CAPS or PCI_FILL_EXT_CAPS
+ * @param cap_number Which instance of a capability to target
+ * @returns          pointer to capability structure or NULL if not found
+ */
+struct pci_cap *
+pci_find_cap_nr(struct pci_dev *d, unsigned int id, unsigned int type,
+                unsigned int *cap_number)
 {
   struct pci_cap *c;
+  unsigned int target = 0;
+  if (cap_number != NULL)
+    {
+      target = *cap_number;
+      *cap_number = 0;
+    }
 
-  pci_fill_info_v35(d, ((type == PCI_CAP_NORMAL) ? PCI_FILL_CAPS : PCI_FILL_EXT_CAPS));
+  pci_fill_info_v35(d, ((type == PCI_CAP_NORMAL)
+                        ? PCI_FILL_CAPS
+                        : PCI_FILL_EXT_CAPS));
   for (c=d->first_cap; c; c=c->next)
     if (c->type == type && c->id == id)
-      return c;
+      if (cap_number == NULL || target == *cap_number)
+        return c;
+      else
+       (*cap_number)++;
   return NULL;
 }
diff --git a/lib/libpci.ver b/lib/libpci.ver
index d15e678..e20c3f5 100644
--- a/lib/libpci.ver
+++ b/lib/libpci.ver
@@ -77,3 +77,8 @@ LIBPCI_3.6 {
 	global:
 		pci_get_string_property;
 };
+
+LIBPCI_3.7 {
+	global:
+		pci_find_cap_nr;
+};
diff --git a/lib/pci.h b/lib/pci.h
index 548aa69..ae9689d 100644
--- a/lib/pci.h
+++ b/lib/pci.h
@@ -211,6 +211,8 @@ struct pci_cap {
 #define PCI_CAP_EXTENDED	2	/* PCIe extended capabilities */
 
 struct pci_cap *pci_find_cap(struct pci_dev *, unsigned int id, unsigned int type) PCI_ABI;
+struct pci_cap *pci_find_cap_nr(struct pci_dev *, unsigned int id, unsigned int type,
+                             unsigned int *cap_number) PCI_ABI;
 
 /*
  *	Filters
-- 
2.39.2