DM USB: xHCI: refine port assignment logic

The variable native_assign_ports in struct pci_xhci_vdev is used
to record wether certain root hub port in SOS is assigned to UOS.
The logic uses zero to express 'not assigned' and nonzero to express
'assigned'. In this patch, use macro to replace number to express
better.

Signed-off-by: Xiaoguang Wu <xiaoguang.wu@intel.com>
Reviewed-by: Liang Yang <liang3.yang@intel.com>
Acked-by: Yu Wang <yu1.wang@intel.com>

Author: xiaoguangwu

devicemodel/hw/pci/xhci.c

@@ -384,6 +384,10 @@ struct pci_xhci_vdev {
 #define	XHCI_HALTED(xdev)	((xdev)->opregs.usbsts & XHCI_STS_HCH)
 #define	XHCI_GADDR(xdev, a)	paddr_guest2host((xdev)->dev->vmctx, (a), \
 				XHCI_PADDR_SZ - ((a) & (XHCI_PADDR_SZ-1)))
+
+#define VPORT_FREE (0)
+#define VPORT_ASSIGNED (-1)
+
 struct pci_xhci_option_elem {
 	char *parse_opt;
 	int (*parse_fn)(struct pci_xhci_vdev *, char *);
@@ -500,7 +504,7 @@ pci_xhci_native_usb_dev_conn_cb(void *hci_data, void *dev_data)
 	UPRINTF(LDBG, "%04x:%04x %d-%d connecting.\r\n",
 			di->vid, di->pid, di->bus, di->port);
 
-	if (!xdev->native_assign_ports[di->bus][di->port]) {
+	if (xdev->native_assign_ports[di->bus][di->port] == VPORT_FREE) {
 		UPRINTF(LDBG, "%04x:%04x %d-%d doesn't belong to this vm, bye."
 				"\r\n", di->vid, di->pid, di->bus, di->port);
 		goto errout;
@@ -3360,7 +3364,7 @@ pci_xhci_parse_bus_port(struct pci_xhci_vdev *xdev, char *opts)
 		goto errout;
 	}
 
-	xdev->native_assign_ports[bus][port] = 1;
+	xdev->native_assign_ports[bus][port] = VPORT_ASSIGNED;
 errout:
 	if (rc)
 		UPRINTF(LWRN, "%s fails, rc=%d\r\n", __func__, rc);