[Qemu-devel] [PULL 3/3] input: Add trace event for empty keyboard queue

[Gerd Hoffmann]

From: Alexander Graf <address@hidden>

When driving QEMU from the outside, we have basically no chance to
determine how quickly the guest OS picks up key events, so we usually
have to limit ourselves to very slow keyboard presses to make sure
the guest always has enough chance to pick them up.

This patch adds a trace events when the keyboarde queue is drained.
An external driver can use that as hint that new keys can be pressed.

Signed-off-by: Alexander Graf <address@hidden>
Message-id: address@hidden
Signed-off-by: Gerd Hoffmann <address@hidden>
---
 hw/input/hid.c        | 4 ++++
 hw/input/trace-events | 1 +
 2 files changed, 5 insertions(+)

diff --git a/hw/input/hid.c b/hw/input/hid.c
index fa9cc4c616..93887ecc43 100644
--- a/hw/input/hid.c
+++ b/hw/input/hid.c
@@ -256,6 +256,10 @@ static void hid_keyboard_process_keycode(HIDState *hs)
     slot = hs->head & QUEUE_MASK; QUEUE_INCR(hs->head); hs->n--;
     keycode = hs->kbd.keycodes[slot];
 
+    if (!hs->n) {
+        trace_hid_kbd_queue_empty();
+    }
+
     key = keycode & 0x7f;
     index = key | ((hs->kbd.modifiers & (1 << 8)) >> 1);
     hid_code = hid_usage_keys[index];
diff --git a/hw/input/trace-events b/hw/input/trace-events
index f3bfbede5c..5a87818b49 100644
--- a/hw/input/trace-events
+++ b/hw/input/trace-events
@@ -24,6 +24,7 @@ milkymist_softusb_pulse_irq(void) "Pulse IRQ"
 
 # hw/input/hid.c
 hid_kbd_queue_full(void) "queue full"
+hid_kbd_queue_empty(void) "queue empty"
 
 # hw/input/virtio
 virtio_input_queue_full(void) "queue full"
-- 
2.9.3