On Mon, 2020-02-10 at 13:21 +0500, Mikhail Gavrilov wrote:
> Kernel log flooded by message
> logitech-djreceiver 0003:046D:C53A.000C: logi_dj_hidpp_event: invalid
> device index:7
> This happens when the mouse is idle.
> And it started since I begin using the mouse pad with Power Play
> technology.
> 
> 
> Kernel ver: 5.6 pre RC
> --
> Best Regards,
> Mike Gavrilov.

Hello Mike,

Yes, the Powerplay mat exports a static HID++ 2.0 device with index 7
to configure the led on the mat. The current code expects devices to
have a maximum index of 6, which is the maximum index of pairable
devices. 

I already submitted a patch adding support for the Logitech G Powerplay
mat but it wasn't been upstreamed it. I will attach it in case you want
to try it.

Cheers,
Filipe Laíns

---
Author: Filipe Laíns <lains@archlinux.org>
Date:   Sun Jan 12 20:15:41 2020 +0000

    HID: logitech-dj: add support for the static device in the Powerplay mat/receiver

    The Logitech G Powerplay has a lightspeed receiver with a static HID++
    device with ID 7 attached to it to. It is used to configure the led on
    the mat. For this reason I increased the max number of devices.

    Signed-off-by: Filipe Laíns <lains@archlinux.org>

diff --git a/drivers/hid/hid-logitech-dj.c b/drivers/hid/hid-logitech-dj.c
index bb50d6e7745b..79294b873057 100644
--- a/drivers/hid/hid-logitech-dj.c
+++ b/drivers/hid/hid-logitech-dj.c
@@ -16,11 +16,11 @@
 #include <asm/unaligned.h>
 #include "hid-ids.h"

-#define DJ_MAX_PAIRED_DEVICES                  6
+#define DJ_MAX_PAIRED_DEVICES                  7
 #define DJ_MAX_NUMBER_NOTIFS                   8
 #define DJ_RECEIVER_INDEX                      0
 #define DJ_DEVICE_INDEX_MIN                    1
-#define DJ_DEVICE_INDEX_MAX                    6
+#define DJ_DEVICE_INDEX_MAX                    7

 #define DJREPORT_SHORT_LENGTH                  15
 #define DJREPORT_LONG_LENGTH                   32
@@ -980,6 +980,11 @@ static void logi_hidpp_recv_queue_notif(struct hid_device *hdev,
                break;
        }

+       /* custom receiver device (eg. powerplay) */
+       if (hidpp_report->device_index == 7) {
+               workitem.reports_supported |= HIDPP;
+       }
+
        if (workitem.type == WORKITEM_TYPE_EMPTY) {
                hid_warn(hdev,
                         "unusable device of type %s (0x%02x) connected on slot %d",