[PATCH] Input: only send a syn event when needed in input_dev_release_keys

[Hans Holmberg <hans.holmberg@intel.com>]

A SYN event is reported in input_release_keys even if no keys are
released. Stop doing this as the superfluous event can prevent autosleep
if a user has opened a device with EPOLLWAKEUP enabled.

Based on a patch developed by Ting Li <ting.li@intel.com>.

Signed-off-by: Hans Holmberg <hans.holmberg@intel.com>
---
 drivers/input/input.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 78d2499..c748805 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -675,12 +675,18 @@ EXPORT_SYMBOL(input_close_device);
 static void input_dev_release_keys(struct input_dev *dev)
 {
 	int code;
+	bool key_released = false;
 
 	if (is_event_supported(EV_KEY, dev->evbit, EV_MAX)) {
-		for_each_set_bit(code, dev->key, KEY_CNT)
+		for_each_set_bit(code, dev->key, KEY_CNT) {
 			input_pass_event(dev, EV_KEY, code, 0);
-		memset(dev->key, 0, sizeof(dev->key));
-		input_pass_event(dev, EV_SYN, SYN_REPORT, 1);
+			key_released = true;
+		}
+
+		if (key_released) {
+			memset(dev->key, 0, sizeof(dev->key));
+			input_pass_event(dev, EV_SYN, SYN_REPORT, 1);
+		}
 	}
 }
 
-- 
1.9.1