[PATCH v4 10/16] libqos: add iteration support to qpci_find_capability()

[Stefan Hajnoczi <stefanha@redhat.com>]

VIRTIO 1.0 PCI devices have multiple PCI_CAP_ID_VNDR capabilities so we
need a way to iterate over them.  Extend qpci_find_capability() to take
the last address.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
--
v3:
 * Document qpci_find_capability()
---
 tests/libqos/pci.h |  2 +-
 tests/libqos/pci.c | 30 ++++++++++++++++++++++++------
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/tests/libqos/pci.h b/tests/libqos/pci.h
index a5389a5845..590c175190 100644
--- a/tests/libqos/pci.h
+++ b/tests/libqos/pci.h
@@ -86,7 +86,7 @@ bool qpci_has_buggy_msi(QPCIDevice *dev);
 bool qpci_check_buggy_msi(QPCIDevice *dev);
 
 void qpci_device_enable(QPCIDevice *dev);
-uint8_t qpci_find_capability(QPCIDevice *dev, uint8_t id);
+uint8_t qpci_find_capability(QPCIDevice *dev, uint8_t id, uint8_t start_addr);
 void qpci_msix_enable(QPCIDevice *dev);
 void qpci_msix_disable(QPCIDevice *dev);
 bool qpci_msix_pending(QPCIDevice *dev, uint16_t entry);
diff --git a/tests/libqos/pci.c b/tests/libqos/pci.c
index 662ee7a517..2309a724e4 100644
--- a/tests/libqos/pci.c
+++ b/tests/libqos/pci.c
@@ -115,10 +115,28 @@ void qpci_device_enable(QPCIDevice *dev)
     g_assert_cmphex(cmd & PCI_COMMAND_MASTER, ==, PCI_COMMAND_MASTER);
 }
 
-uint8_t qpci_find_capability(QPCIDevice *dev, uint8_t id)
+/**
+ * qpci_find_capability:
+ * @dev: the PCI device
+ * @id: the PCI Capability ID (PCI_CAP_ID_*)
+ * @start_addr: 0 to begin iteration or the last return value to continue
+ *              iteration
+ *
+ * Iterate over the PCI Capabilities List.
+ *
+ * Returns: PCI Configuration Space offset of the capabililty structure or
+ *          0 if no further matching capability is found
+ */
+uint8_t qpci_find_capability(QPCIDevice *dev, uint8_t id, uint8_t start_addr)
 {
     uint8_t cap;
-    uint8_t addr = qpci_config_readb(dev, PCI_CAPABILITY_LIST);
+    uint8_t addr;
+
+    if (start_addr) {
+        addr = qpci_config_readb(dev, start_addr + PCI_CAP_LIST_NEXT);
+    } else {
+        addr = qpci_config_readb(dev, PCI_CAPABILITY_LIST);
+    }
 
     do {
         cap = qpci_config_readb(dev, addr);
@@ -138,7 +156,7 @@ void qpci_msix_enable(QPCIDevice *dev)
     uint8_t bir_table;
     uint8_t bir_pba;
 
-    addr = qpci_find_capability(dev, PCI_CAP_ID_MSIX);
+    addr = qpci_find_capability(dev, PCI_CAP_ID_MSIX, 0);
     g_assert_cmphex(addr, !=, 0);
 
     val = qpci_config_readw(dev, addr + PCI_MSIX_FLAGS);
@@ -167,7 +185,7 @@ void qpci_msix_disable(QPCIDevice *dev)
     uint16_t val;
 
     g_assert(dev->msix_enabled);
-    addr = qpci_find_capability(dev, PCI_CAP_ID_MSIX);
+    addr = qpci_find_capability(dev, PCI_CAP_ID_MSIX, 0);
     g_assert_cmphex(addr, !=, 0);
     val = qpci_config_readw(dev, addr + PCI_MSIX_FLAGS);
     qpci_config_writew(dev, addr + PCI_MSIX_FLAGS,
@@ -203,7 +221,7 @@ bool qpci_msix_masked(QPCIDevice *dev, uint16_t entry)
     uint64_t vector_off = dev->msix_table_off + entry * PCI_MSIX_ENTRY_SIZE;
 
     g_assert(dev->msix_enabled);
-    addr = qpci_find_capability(dev, PCI_CAP_ID_MSIX);
+    addr = qpci_find_capability(dev, PCI_CAP_ID_MSIX, 0);
     g_assert_cmphex(addr, !=, 0);
     val = qpci_config_readw(dev, addr + PCI_MSIX_FLAGS);
 
@@ -221,7 +239,7 @@ uint16_t qpci_msix_table_size(QPCIDevice *dev)
     uint8_t addr;
     uint16_t control;
 
-    addr = qpci_find_capability(dev, PCI_CAP_ID_MSIX);
+    addr = qpci_find_capability(dev, PCI_CAP_ID_MSIX, 0);
     g_assert_cmphex(addr, !=, 0);
 
     control = qpci_config_readw(dev, addr + PCI_MSIX_FLAGS);
-- 
2.21.0