[PATCH 3/7] Figure out device capability

[Sheng Yang <sheng@linux.intel.com>]

Try to figure out device capability in update_dev_cap(). Now we are only care
about MSI capability.

The function pci_find_cap_offset original function wrote by Allen for Xen.
Notice the function need root privilege to work. This depends on libpci to work.

Signed-off-by: Allen Kay <allen.m.kay@intel.com>
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
---
 qemu/hw/device-assignment.c |   29 +++++++++++++++++++++++++++++
 qemu/hw/device-assignment.h |    1 +
 2 files changed, 30 insertions(+), 0 deletions(-)

diff --git a/qemu/hw/device-assignment.c b/qemu/hw/device-assignment.c
index f14f971..76369ed 100644
--- a/qemu/hw/device-assignment.c
+++ b/qemu/hw/device-assignment.c
@@ -219,6 +219,35 @@ static void assigned_dev_ioport_map(PCIDevice *pci_dev, int region_num,
                           (r_dev->v_addrs + region_num));
 }
 
+static uint8_t pci_find_cap_offset(struct pci_dev *pci_dev, uint8_t cap)
+{
+    int id;
+    int max_cap = 48;
+    int pos = PCI_CAPABILITY_LIST;
+    int status;
+
+    status = pci_read_byte(pci_dev, PCI_STATUS);
+    if ((status & PCI_STATUS_CAP_LIST) == 0)
+        return 0;
+
+    while (max_cap--) {
+        pos = pci_read_byte(pci_dev, pos);
+        if (pos < 0x40)
+            break;
+
+        pos &= ~3;
+        id = pci_read_byte(pci_dev, pos + PCI_CAP_LIST_ID);
+
+        if (id == 0xff)
+            break;
+        if (id == cap)
+            return pos;
+
+        pos += PCI_CAP_LIST_NEXT;
+    }
+    return 0;
+}
+
 static void assigned_dev_pci_write_config(PCIDevice *d, uint32_t address,
                                           uint32_t val, int len)
 {
diff --git a/qemu/hw/device-assignment.h b/qemu/hw/device-assignment.h
index f216bb0..f8b8e65 100644
--- a/qemu/hw/device-assignment.h
+++ b/qemu/hw/device-assignment.h
@@ -29,6 +29,7 @@
 #define __DEVICE_ASSIGNMENT_H__
 
 #include <sys/mman.h>
+#include <pci/pci.h>
 #include "qemu-common.h"
 #include "sys-queue.h"
 #include "pci.h"
-- 
1.5.4.5