USB HID does not support Set_Idle

I found that the QEMU USB keyboard support does not work properly with
the Set_Idle command.  Once a non-zero value is given to Set_Idle,
then the keyboard reports an event on every poll - not based on the
time issued in the Set_Idle command.

I changed the code (see patch below) and it works for me.  I'm not
that familiar with the qemu internals, so I'm not sure if this is the
best way to implement this feature.

-Kevin
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/usb-hid.c

@@ -66,6 +66,7 @@ typedef struct USBHIDState {
     int kind;
     int protocol;
     uint8_t idle;
+    int64_t next_idle_clock;
     int changed;
     void *datain_opaque;
     void (*datain)(void *);
@@ -630,6 +631,11 @@ static void usb_keyboard_handle_reset(USBDevice *dev)
     s->protocol = 1;
 }
 
+static void usb_hid_set_next_idle(USBHIDState *s, int64_t curtime)
+{
+    s->next_idle_clock = curtime + (get_ticks_per_sec() * s->idle * 4) / 1000;
+}
+
 static int usb_hid_handle_control(USBDevice *dev, int request, int value,
                                   int index, int length, uint8_t *data)
 {
@@ -795,6 +801,7 @@ static int usb_hid_handle_control(USBDevice *dev, int request, int value,
         break;
     case SET_IDLE:
         s->idle = (uint8_t) (value >> 8);
+        usb_hid_set_next_idle(s, qemu_get_clock(vm_clock));
         ret = 0;
         break;
     default:
@@ -813,9 +820,10 @@ static int usb_hid_handle_data(USBDevice *dev, USBPacket *p)
     switch(p->pid) {
     case USB_TOKEN_IN:
         if (p->devep == 1) {
-            /* TODO: Implement finite idle delays.  */
-            if (!(s->changed || s->idle))
+            int64_t curtime = qemu_get_clock(vm_clock);
+            if (!s->changed && (!s->idle || s->next_idle_clock - curtime > 0))
                 return USB_RET_NAK;
+            usb_hid_set_next_idle(s, curtime);
             s->changed = 0;
             if (s->kind == USB_MOUSE)
                 ret = usb_mouse_poll(s, p->data, p->len);