From 9bfc8da00b1e74f55a52cc06a0d364f1f7f61ed8 Mon Sep 17 00:00:00 2001
From: Henrik Rydberg <rydberg@euromail.se>
Date: Sat, 1 Sep 2012 21:47:11 +0200
Subject: [PATCH] HID: Only dump input if someone is listening
Going through the motions of printing the debug message information
takes a long time; using the keyboard can lead to a 160 us irqsoff
latency. This patch skips hid_dump_input() when there are no open
handles, which brings latency down to 100 us.
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
---
drivers/hid/hid-core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 8bf8a64e51154..b8485a0106c97 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -996,7 +996,8 @@ static void hid_process_event(struct hid_device *hid, struct hid_field *field,
struct hid_driver *hdrv = hid->driver;
int ret;
- hid_dump_input(hid, usage, value);
+ if (!list_empty(&hid->debug_list))
+ hid_dump_input(hid, usage, value);
if (hdrv && hdrv->event && hid_match_usage(hid, usage)) {
ret = hdrv->event(hid, field, usage, value);
--
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