[PATCH] HID: hid-input: avoid splitting keyboard, system and consumer controls

[Dmitry Torokhov]

A typical USB keyboard usually splits its keys into several reports:

- one for the basic alphanumeric keys, modifier keys, F<n> keys, six pack
  keys and keypad. This report's application is normally listed as
  GenericDesktop.Keyboard
- a GenericDesktop.SystemControl report for the system control keys, such
  as power and sleep
- Consumer.ConsumerControl report for multimedia (forward, rewind,
  play/pause, mute, etc) and other extended keys.
- additional output, vendor specific, and feature reports

Splitting each report into a separate input device is wasteful and even
hurts userspace as it makes it harder to determine the true capabilities
(set of available keys) of a keyboard, so let's adjust application
matching to merge system control and consumer control reports with
keyboard report, if one has already been processed.

Signed-off-by: Dmitry Torokhov <dmitry.torok...@gmail.com>
---
 drivers/hid/hid-input.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index f797659cb9d9..df45d8d07dc2 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -1851,6 +1851,16 @@ static struct hid_input 
*hidinput_match_application(struct hid_report *report)
        list_for_each_entry(hidinput, &hid->inputs, list) {
                if (hidinput->application == report->application)
                        return hidinput;
+
+               /*
+                * Keep SystemControl and ConsumerControl applications together
+                * with the main keyboard, if present.
+                */
+               if ((report->application == HID_GD_SYSTEM_CONTROL ||
+                    report->application == HID_CP_CONSUMER_CONTROL) &&
+                   hidinput->application == HID_GD_KEYBOARD) {
+                       return hidinput;
+               }
        }
 
        return NULL;
-- 
2.30.0.284.gd98b1dd5eaa7-goog


-- 
Dmitry