linux-kernel - Re: [PATCH] HID: logitech-dj: add support for the static device in the Powerplay mat/receiver

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Date:   Wed, 12 Feb 2020 14:50:01 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Filipe Laíns <lains@...hlinux.org>
cc:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HID: logitech-dj: add support for the static device in
 the Powerplay mat/receiver

On Wed, 15 Jan 2020, Filipe Laíns wrote:

> 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@...hlinux.org>
> ---
>  drivers/hid/hid-logitech-dj.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> 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;
> +	}
> +

I guess we can't do anything else than to trust Logitech that they will 
not assign conflicting device_index ID in the future to something that 
will not be HID++, right?

Or is this properly documented somewhere?

Thanks,

-- 
Jiri Kosina
SUSE Labs