Input: evdev - do not queue SYN_DROPPED if queue is empty

There is no point in queueing EV_SYN/SYN_DROPPED on clock type change when
there are no events in the client's queue and doing so confuses tests in
libinput package, so let's not do that.

Reported-and-tested-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

1 files changed, 23 insertions, 11 deletions

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index e7cee3880b75..a18f41b89b6a 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -108,10 +108,8 @@ static void __evdev_flush_queue(struct evdev_client *client, unsigned int type)
         client->head = head;
 }
 
-/* queue SYN_DROPPED event and flush queue if flush parameter is true */
-static void evdev_queue_syn_dropped(struct evdev_client *client, bool flush)
+static void __evdev_queue_syn_dropped(struct evdev_client *client)
 {
-        unsigned long flags;
         struct input_event ev;
         ktime_t time;
 
@@ -126,11 +124,6 @@ static void evdev_queue_syn_dropped(struct evdev_client *client, bool flush)
         ev.code = SYN_DROPPED;
         ev.value = 0;
 
-        spin_lock_irqsave(&client->buffer_lock, flags);
-
-        if (flush)
-                client->packet_head = client->head = client->tail;
-
         client->buffer[client->head++] = ev;
         client->head &= client->bufsize - 1;
 
@@ -139,12 +132,21 @@ static void evdev_queue_syn_dropped(struct evdev_client *client, bool flush)
                 client->tail = (client->head - 1) & (client->bufsize - 1);
                 client->packet_head = client->tail;
         }
+}
+
+static void evdev_queue_syn_dropped(struct evdev_client *client)
+{
+        unsigned long flags;
 
+        spin_lock_irqsave(&client->buffer_lock, flags);
+        __evdev_queue_syn_dropped(client);
         spin_unlock_irqrestore(&client->buffer_lock, flags);
 }
 
 static int evdev_set_clk_type(struct evdev_client *client, unsigned int clkid)
 {
+        unsigned long flags;
+
         if (client->clk_type == clkid)
                 return 0;
 
@@ -163,8 +165,18 @@ static int evdev_set_clk_type(struct evdev_client *client, unsigned int clkid)
                 return -EINVAL;
         }
 
-        /* Flush pending events and queue SYN_DROPPED event.*/
-        evdev_queue_syn_dropped(client, true);
+        /*
+         * Flush pending events and queue SYN_DROPPED event,
+         * but only if the queue is not empty.
+         */
+        spin_lock_irqsave(&client->buffer_lock, flags);
+
+        if (client->head != client->tail) {
+                client->packet_head = client->head = client->tail;
+                __evdev_queue_syn_dropped(client);
+        }
+
+        spin_unlock_irqrestore(&client->buffer_lock, flags);
 
         return 0;
 }
@@ -803,7 +815,7 @@ static int evdev_handle_get_val(struct evdev_client *client,
 
         ret = bits_to_user(mem, maxbit, maxlen, p, compat);
         if (ret < 0)
-                evdev_queue_syn_dropped(client, false);
+                evdev_queue_syn_dropped(client);
 
         kfree(mem);