Add USB option in machine options

When -usb option is used, global varible usb_enabled is set.
And all the plaform will create one USB controller according
to this variable. In fact, global varibles make code hard
to read.

So this patch is to remove global variable usb_enabled and
add USB option in machine options. All the plaforms will get
USB option value from machine options.

USB option of machine options will be set either by:
  * -usb
  * -machine type=pseries,usb=on

Both these ways can work now. They both set USB option in
machine options. In the future, the first way will be removed.

Signed-off-by: Li Zhang <zhlcindy@linux.vnet.ibm.com>
Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/vl.c b/vl.c
index 9f99ef4..eb533b2 100644
--- a/vl.c
+++ b/vl.c
@@ -203,7 +203,6 @@
 CharDriverState *parallel_hds[MAX_PARALLEL_PORTS];
 CharDriverState *virtcon_hds[MAX_VIRTIO_CONSOLES];
 int win2k_install_hack = 0;
-int usb_enabled = 0;
 int singlestep = 0;
 int smp_cpus = 1;
 int max_cpus = 0;
@@ -790,6 +789,17 @@
     return 0;
 }
 
+/*********QEMU USB setting******/
+bool usb_enabled(bool default_usb)
+{
+    QemuOpts *mach_opts;
+    mach_opts = qemu_opts_find(qemu_find_opts("machine"), 0);
+    if (mach_opts) {
+        return qemu_opt_get_bool(mach_opts, "usb", default_usb);
+    }
+    return default_usb;
+}
+
 /***********************************************************/
 /* QEMU Block devices */
 
@@ -1077,8 +1087,9 @@
     const char *p;
     USBDevice *dev = NULL;
 
-    if (!usb_enabled)
+    if (!usb_enabled(false)) {
         return -1;
+    }
 
     /* drivers with .usbdevice_name entry in USBDeviceInfo */
     dev = usbdevice_create(devname);
@@ -1114,8 +1125,9 @@
     if (strstart(devname, "host:", &p))
         return usb_host_device_close(p);
 
-    if (!usb_enabled)
+    if (!usb_enabled(false)) {
         return -1;
+    }
 
     p = strchr(devname, '.');
     if (!p)
@@ -3083,10 +3095,16 @@
                 }
                 break;
             case QEMU_OPTION_usb:
-                usb_enabled = 1;
+                machine_opts = qemu_opts_find(qemu_find_opts("machine"), 0);
+                if (machine_opts) {
+                    qemu_opt_set_bool(machine_opts, "usb", true);
+                }
                 break;
             case QEMU_OPTION_usbdevice:
-                usb_enabled = 1;
+                machine_opts = qemu_opts_find(qemu_find_opts("machine"), 0);
+                if (machine_opts) {
+                    qemu_opt_set_bool(machine_opts, "usb", true);
+                }
                 add_device_config(DEV_USB, optarg);
                 break;
             case QEMU_OPTION_device:
@@ -3653,7 +3671,7 @@
     current_machine = machine;
 
     /* init USB devices */
-    if (usb_enabled) {
+    if (usb_enabled(false)) {
         if (foreach_device_config(DEV_USB, usb_parse) < 0)
             exit(1);
     }