linux-kernel - Re: [PATCH] HID: logitech-dj: issue udev change event on device connection

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Date:   Wed, 18 Mar 2020 19:23:10 +0000
From:   Filipe Laíns <lains@...hlinux.org>
To:     Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Peter Hutterer <peter.hutterer@...hat.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mario Limonciello <superm1@...il.com>,
        Richard Hughes <hughsient@...il.com>
Subject: Re: [PATCH] HID: logitech-dj: issue udev change event on device
 connection

On Wed, 2020-03-18 at 16:19 +0000, Filipe Laíns wrote:
> As discussed in the mailing list:
> 
> > Right now the hid-logitech-dj driver will export one node for each
> > connected device, even when the device is not connected. That
> > causes
> > some trouble because in userspace we don't have have any way to
> > know if
> > the device is connected or not, so when we try to communicate, if
> > the
> > device is disconnected it will fail.
> 
> The solution reached to solve this issue is to trigger an udev change
> event when the device connects, this way userspace can just wait on
> those connections instead of trying to ping the device.
> 
> Signed-off-by: Filipe Laíns <lains@...hlinux.org>
> ---
>  drivers/hid/hid-logitech-dj.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/hid/hid-logitech-dj.c b/drivers/hid/hid-
> logitech-dj.c
> index 48dff5d6b605..fcd481a0be1f 100644
> --- a/drivers/hid/hid-logitech-dj.c
> +++ b/drivers/hid/hid-logitech-dj.c
> @@ -1464,6 +1464,8 @@ static int logi_dj_dj_event(struct hid_device
> *hdev,
>  		if (dj_report-
> >report_params[CONNECTION_STATUS_PARAM_STATUS] ==
>  		    STATUS_LINKLOSS) {
>  			logi_dj_recv_forward_null_report(djrcv_dev,
> dj_report);
> +		} else {
> +			kobject_uevent(&hdev->dev.kobj, KOBJ_CHANGE);
>  		}
>  		break;
>  	default:

Just noticed I was issuing the udev event on the receiver instead of
the connected device. I will send a v2.

Filipe Laíns

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