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Subject[PATCH v3 16/20] HID: Only dump input if someone is listening
Date
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>
---
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 60ea284..5b74e78 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);
--
1.7.12


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