virtio-input: add input routing support

Add display and head properties for input routing to
virtio-input devices, update multiseat documentation.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

docs/multiseat.txt

@@ -2,8 +2,8 @@
 multiseat howto (with some multihead coverage)
 ==============================================
 
-host side
----------
+host devices
+------------
 
 First you must compile qemu with a user interface supporting
 multihead/multiseat and input event routing.  Right now this
@@ -41,6 +41,19 @@ The "display=video2" sets up the input routing.  Any input coming from
 the window which belongs to the video.2 display adapter will be routed
 to these input devices.
 
+Starting with qemu 2.4 and linux kernel 4.1 you can also use virtio
+for the input devices, using this ...
+
+	-device pci-bridge,addr=12.0,chassis_nr=2,id=head.2 \
+	-device secondary-vga,bus=head.2,addr=02.0,id=video.2 \
+	-device virtio-keyboard-pci,bus=head.2,addr=03.0,display=video.2 \
+	-device virtio-tablet-pci,bus=head.2,addr=03.0,display=video.2
+
+... instead of xhci and usb hid devices.
+
+host ui
+-------
+
 The sdl2 ui will start up with two windows, one for each display
 device.  The gtk ui will start with a single window and each display
 in a separate tab.  You can either simply switch tabs to switch heads,

hw/input/virtio-input-hid.c

@@ -252,7 +252,11 @@ static void virtio_input_handle_sync(DeviceState *dev)
 static void virtio_input_hid_realize(DeviceState *dev, Error **errp)
 {
     VirtIOInputHID *vhid = VIRTIO_INPUT_HID(dev);
+
     vhid->hs = qemu_input_handler_register(dev, vhid->handler);
+    if (vhid->display && vhid->hs) {
+        qemu_input_handler_bind(vhid->hs, vhid->display, vhid->head, NULL);
+    }
 }
 
 static void virtio_input_hid_unrealize(DeviceState *dev, Error **errp)
@@ -301,10 +305,17 @@ static void virtio_input_hid_handle_status(VirtIOInput *vinput,
     }
 }
 
+static Property virtio_input_hid_properties[] = {
+    DEFINE_PROP_STRING("display", VirtIOInputHID, display),
+    DEFINE_PROP_UINT32("head", VirtIOInputHID, head, 0),
+};
+
 static void virtio_input_hid_class_init(ObjectClass *klass, void *data)
 {
+    DeviceClass *dc = DEVICE_CLASS(klass);
     VirtIOInputClass *vic = VIRTIO_INPUT_CLASS(klass);
 
+    dc->props          = virtio_input_hid_properties;
     vic->realize       = virtio_input_hid_realize;
     vic->unrealize     = virtio_input_hid_unrealize;
     vic->change_active = virtio_input_hid_change_active;

include/hw/virtio/virtio-input.h

@@ -95,6 +95,8 @@ struct VirtIOInputClass {
 
 struct VirtIOInputHID {
     VirtIOInput                       parent_obj;
+    char                              *display;
+    uint32_t                          head;
     QemuInputHandler                  *handler;
     QemuInputHandlerState             *hs;
     int                               ledstate;